Dissertations / Theses on the topic 'Wood science'

In an effort to comprehensively study the wood property variation in juvenile wood, compression wood, and mature wood, and also to provide a rapid and cost-effective assessment tool to screening the wood chemical property variation, several loblolly pines (Pinus tadea), and transmittance near infrared spectroscopy were utilized in this study. The method development results show that a successful screening of wood chemical property variation, such as lignin and á-cellulose contents, could be adapted using stacked wood wafers microtomed from increment cores and combining with transmittance near infrared spectroscopy. The morphological, chemical, and metabolic analyses of juvenile wood and compression wood show that although compression wood and juvenile wood share some properties, they are actually distinct in their chemistry during development and in final wood chemistry and anatomy. The within tree variation analyses also show that juvenile wood from the top of the tree and that from the base of the tree are more different in morphological structures than in chemical structures. A similar pattern was found between juvenile wood and mature wood. The results obtained suggest that the within tree compression wood percentage and the fiber quality differences inherent in juvenile wood appear to have a greater influence on the final wood products.

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: The effects of the macromolecular composition and content of different wood species on the properties of wood-polymer composites (WPCs) achieved when using poly(vinyl alcohol-co-ethylene) (EVOH) as a compatibiliser and linear low density polyethylene (LLDPE) as a matrix, were investigated. Four wood different species (A. cyclops (acacia), E. grandis (eucalyptus), P. radiata (pine) and Q. alba (oak)) with different macromolecular composition and contents and average particle lengths were used. WPCs filled with these species and WPCs filled with the same species but without extractives were prepared using 10% wood content and different amounts (0, 2, 5, 7 and 10%) of EVOH. An EVOH content of 7% was found to be optimum. Unextracted woods produced WPCs with higher mechanical properties and better resistance to ultraviolet (UV) degradation, while the extracted woods produced WPCs with lower water absorption (WA) rates and better thermal stability. Use of unextracted A. cyclops resulted in composites with superior mechanical and thermal properties compared with the other unextracted species, most probably due to its higher cellulose and lignin contents and a favourable average wood particle length (0.225 mm). A. cyclops composites also had higher WA and thickness swelling (TS) rates most likely due to the greater number of free hydroxyl groups present in these composites because of higher cellulose content. Composites containing wood species with a high lignin and extractive content, such as A. cyclops and Q. alba, exhibited higher resistance to UV degradation. Poly(vinyl alcohol-co-ethylenes) (EVOHs) with different ethylene content (27, 32, 38 and 44%) and A. cyclops with different particle sizes (180, 250 and 450 ìm) were used to prepare WPCs with 10% A. cyclops content. The effect of the contact area between the A. cyclops particles and LLDPE achieved when using EVOHs as compatibilisers on the properties of WPCs was also investigated. The greatest improvements in the mechanical and thermal properties of composites made with A. cyclops with particle size 180 ìm were obtained when EVOH with 44% ethylene content was used. The greatest improvements in the composites made with A. cyclops with particle size 250 ìm were achieved when EVOH with 38% ethylene content was used. Composites made with A. cyclops with particle size 450 ìm exhibited better properties when EVOH with 27% ethylene content was used. All the composites that had better mechanical and thermal properties, also exhibited better compatibility and interface adhesion. Two successful approaches were used to impart more attractive ecological and economical advantages to WPCs. In the first approach, (0, 2, 5 and 7%) degraded LLDPE was used as a compatibiliser in WPCs at levels of 10, 30 and 50% wood content. The resulting mechanical properties, such as tensile strength and hardness, thermal and morphological properties of the compatibilised composites were slightly higher than those of noncompatibilised composites and virgin LLDPE. Elongation at break and impact properties of the compatibilised composites were lower than in virgin LLDPE, but higher than in noncompatibilised composites. In the second approach, polyethylene (PE) and various functionalised polyethylenes (PEs) were synthesised by copolymerising ethylene and 10-undecen-1-ol using a soluble metallocene/methylaluminoxane catalyst at room temperature. The incorporation of functional groups increased with increasing comonomer content. WPCs with 10 and 30% wood content were prepared. The composites prepared with functionalised PEs had better mechanical, thermal and morphogical properties than the composites prepared with PE. Composites made with functionalised PE with higher hydroxyl groups content exhibited better properties than composites made with functionalised PE with lower hydroxyl groups content. Composites with 10% wood content exhibited better properties and performance than composites with 30% wood content.
AFRIKAANSE OPSOMMING: Die gevolg van die makromolekulere samestelling van verskillende houtspesies op die eienskappe van hout-polimeer saamgestelde materiale (HPS) wanneer poli(viniel alcohol-ko-etileen) (EVOH) as versoeningsmiddel gebruik word saam met linieere lae digtheid poli(etileen) (LLDPE) as matriks is ondersoek. Vier houtspesies (A. cyclops (acacia), E. grandis (eucalyptus), P. radiata (pine) and Q. alba (oak)) met verskillende makromolekulere samestelling and partikelgrootte-verspreiding is gebruik in die studie. HPS materiale is berei met hierdie vesels, beide voor en na ekstraksie van die houtpartikels met onderskeidelik warm water en oplosmiddels (alleen en in kombinasie). In hierdie HPS materiale is 10% hout gebruik en 0, 2, 5, 7 en 10% EVOH. 'n EVOH inhoud van 7% is as optimum bepaal. Houtpartikels voor ekstraksie het HPS materiale met beter meganiese eienskappe en beter weerstand teen UV bestraling, terwyle partikels wat ekstraksie ondergaan het HPS materiale met laer water-absorpsie en beter hitte-stabiliteit to gevolg gehad het. Die gebruik van ongeekstraheerde A. cyclops het samegestelde materiale met die beste meganiese en termiese eienskappe tot gevolg gehad in vergelyking met die ander houtspesies (voor ekstraksie), as gevolg van die hoer sellulose en lignien inhoud van die spesie, sowel as 'n voordelige partikelgrootte-verspreiding. A. Cyclops saamgestelde materiale he took hoer waterabsorpsie (WA) en dikte-swelling (DS) tempos gehad, weens die groter hoeveelheid vrye hidroksielgroepe teenwoording in die materiale, direk in verwantskap met die sellulose-inhoud. Saamgestelde materiale met 'n hoe hoevellheid lignien en ekstraheerbare materiale (A. cyclops and Q. alba) het beter weerstand teen UV-degradasie geopenbaar. Verskillende poli(viniel alkohol-ko-etileen) polimere (EVOHs) met wisselende etileen-inhoud (27, 32, 38 en 44%) en A. Cyclops met verskillende partikel-groottes (180, 250 en 250 µm) is gebruik om HPS materiale met 10% hout te vervaardig. Die gevolg van die kontak-area tussen die houtpartikels en die LLDPE wanneer EVOHs as versoeningsmiddel gebruik is, is ook ondersoek. Die beste verbetering in die meganiese en termiese eienskappe van die saamgestelde materiale met A. cyclops met partikel-grootte 180 µm is gekry met EVOH met 44% etileen-inhoud, terwyl die beste resultate met 250 µm partikels verkry is met 'n EVOH met 38% etileen, en met 27% etileen in die geval van die 450 µm partikels. Twee benaderinge om meer aantreklike ekologiese en ekonomiese eienskappe by die HPS materiale te bewerkstellig was suksesvol. In die eerste geval is gedegradeerde LLDPE as versoeningsmiddel gebruik. Die resulterende meganiese eienskappe van die HPS materiale met LLDPE as versoeningsmiddel was beter as die HPS mateirale daarsonder. Samegestelde materiale met 10, 30 en 50% hout is vervaardig. Die trekverlenging by die breekpunt sowel as die impaksterkte van die HPS materiale was laer as LLDPE alleen, maar beter as die nie-versoende HPS materiale. In die tweede benadering is polietileen (PE) en gefunksionaliseerde PE gesintetiseer deur etileen en 10-undekeen-1-ol te koplimeriseer met ‘n oplosbare metalloseen/metiel alumoksaan katalis. Die hoeveelheid funskionele (OH) groepe is verhoog deur toenemend ekomonommer-inhoud. HPS materiale met 10 en 30% hout is vervaardig. Die saamgestelde materiale met funksionele PE het beter maganiese eienskappe gehad as die met gewone PE. Hoe hoër die hidroksielgroep-inhoud, hoe beter die eienskappe van die HPS materiale, terwyl die materiale met 10% hout beter eienskappe openbaar het as materiale met 30% hout.

The need for sustainability, increasingly requires developing products according to a cradle to cradle approach. For furniture, wood, being potentially renewable, is a suitable material in this regard. However, most wooden furniture today utilizes steels and synthetic polymers in the joints, which can partially be recycled, but are far from being circular materials. All-wood joints have been used in traditional furniture and construction, but they are not adapted to modern manufacturing techniques and do not fulfill the need for easy assembly.  The aim of this thesis is to explore existing solutions for all-wood joints, as well as relevant manufacturing techniques to create an approach for the development of new joints by practitioners. The research questions are: What are the principles used in existing technical solutions and how can they be used to develop new all-wood furniture joints? What are the most important manufacturing techniques for wood today and how can they be considered in the early-stage development? The general approach in this thesis is to abstract the researched existing technical solutions and manufacturing techniques, ideate on this abstract level, and then detail the concepts on a more concrete level.  As results, fourteen different principles and six different patterns of transformation were extracted from existing solutions and documented in an accessible form. Similarly, seven manufacturing techniques were collected and documented. These were then used in an ideation workshop with practitioners from IKEA, which resulted in six abstract concepts. One of the concepts was further developed into a pre-design and tested with a simulations according to strength and stability requirements from applicable standards.  The testing of the pre-design proved its practicality and a team at IKEA is continuing the development of the concept and planning to manufacture a prototype. This is a good indicator for the usefulness of the approach. Even though it worked well, further exploration of the "toolbox" is recommended, as well as the use of different ideation methods. The full environmental benefits of furniture with all-wood joints are not clear, because only resource depletion was considered and the potential effect is small compared to other industries. Despite this, the thesis shows the potential in circular furniture and encourages IKEA and other furniture companies to delve into the topic of circular furniture more deeply.

Wood dynamics that store, transport, break down, and ultimately export wood pieces through watershed networks are key elements of stream complexity and ecosystem health. Efforts to quantify wood processes are advancing rapidly as technological innovations in field data collection, remotely sensed data acquisition, and data analyses become increasingly sophisticated. The ability to extend the temporal and spatial scales of wood data acquisition has been particularly useful to the investigations presented herein. The primary contributions of this dissertation are focused on two aspects of wood dynamics: watershed-scale wood export processes as identified using the depositional environment of a mountain reservoir, and wood deposition mechanisms in a bedrock-dominated mountain river. Three chapters present this work:

In Chapter 1, continuous video monitoring of wood in transport revealed seasonal and diurnal hydrologic cycle influences on the variable rates at which wood transports. This effort supports the efficacy of utilizing continuous data collection methods for wood transport studies. Annual wood export data were collected via field efforts and aerial image analyses from New Bullards Bar Reservoir on the North Yuba River, Sierra Nevada, California. Examination of data revealed linkages between decadal-scale climatic patterns, large flood events, and episodic wood export quantities. A watershed-specific relation between wood export quantities and annual peak discharge contributes to the notion that peak discharge is a primary control on wood export, and yielded prediction of annual wood export quantities where no data were available. Linkages between seasonality, climatic components, and hydrologic events that exert variable control on watershed scale wood responses are presented as a functional framework. An accompanying conceptual model supports the framework presumption that wood responses are influenced by seasonal variations in Mediterranean-montane climate conditions and accompanying hydrologic responses.

Chapter 2 contains development of new theory in support of the introduction of multiplicative coefficients, categorized by water year type, that were used to predict wood export quantities via utilization of an existing discharge-based theoretical equation. This new theory was the product of continued investigations into watershed-scale factors in search of explanation of observed variation of wood export rates into New Bullards Bar Reservoir. The gap between known variability and the attribution of wood export to one hydrologic relation continues to be a persistent issue, as the hierarchical and stochastic temporal and spatial nature of wood budget components remain difficult to quantify. The development of “watershed processes” coefficients was specifically focused on a generalized, parsimonious approach using water year type categories, with validation exercises supporting the approach. In dry years, predictions more closely represented observed wood export quantities, whereas the previously derived annual peak discharge relation yielded large over-predictions. Additional data are needed to continue development of these watershed-specific coefficients. This new approach to wood export prediction may be beneficial in regulated river systems for planning purposes, and its efficacy could be tested in other watersheds.

Chapter 3 presents the results of an investigation into wood deposition mechanisms in a 12.2 km segment of the confined, bedrock-dominated South Yuba River watershed. Inclusion of coarse wood particles in the analyses was essential in recognizing depositional patterns, thus supporting the value of utilizing a wider wood-size range. A near-census data collection effort yielded myriad data, of which topographic wetted width and bed elevation data, developed for an observed 4.5-year flood event, were standardized in 10-m intervals and then univariate and linked values were ordered into landform classifications using decision tree analyses. Digital imagery collected via kite-blimp was mosaicked into a geographic information system and all resolvable wood pieces greater then 2.5 cm in one dimension were delineated and categorized into piece count density classes. Visual imagery was also key in identifying two river corridor terrains: bedrock outcrops and cobble-boulder-vegetation patches. A conceptual model framed an investigation into how topographic variability and structural elements might influence observed wood deposition dynamics. Forage ratio test results that quantified wood piece utilization versus interval availability revealed that high-density wood deposition patterns were most significantly co-located with five discrete bedrock outcrops that dominated small portions of the river corridor in high flow conditions. Topographic variations and cobble-boulder-vegetation patches were found to be subordinate factors in wood deposition patterns. Bedrock outcrops with specific structural components were the primary depositional environments that acted as floodplain extents for coarse wood deposition, with mechanisms such as topographic steering, eddying, trapping, stranding, backwater effects, and lateral roughness features inferred to be responsible for observed wood deposition patterns.

Thesis (MSc)--University of Stellenbosch, 2011.
ENGLISH ABSTRACT: High molar mass tannin extracts are complex mixtures which are distributed in both molar mass and chemical composition. Condensed tannins from quebracho and mimosa and hydrolysable tannins of tara, chestnut wood and turkey gall were studied. Application of a single analytical technique is not sufficient to elucidate the complete structures present in the extracts. 13C Nuclear Magnetic Resonance (NMR) spectroscopy and Matrix Assisted Laser Desorption/Ionisation Time-of-Flight (MALDI-TOF) mass spectrometry were applied in order to determine the chemical composition and molar mass, respectively. A new mass spectrometric method that can uniquely determine the oligomer microstructure was developed using Collision Induced Dissociation (CID) experiments. Bulk analysis only showed the average composition of the extracts, in order to obtain specific information on the molar mass and chemical composition distributions. Hydrophilic Interaction Liquid Chromatography (HILIC) was used for analysis of the condensed tannins and for the hydrolysable tannins Normal Phase Liquid Chromatography (NP-LC) was utilised. The HILIC separation was up-scaled and the fractions were collected and analysed by MALDI-TOF, and this coupling revealed that separation occurs by molar and chemical composition. For separation of the molecules only by size, Size Exclusion Chromatography (SEC) analyses were carried out; this allowed for relative comparison of the tannin molecules. In conclusion, for characterisation of high molar mass tannins a multi-dimensional approach was necessary since the various distributions present in these extracts are superimposed.
AFRIKAANSE OPSOMMING: Hoë molekulêre massa tannienekstrakte is komplekse mengsels, in terme van beide molekulêre massa en chemiese samestelling. Gekondenseerde tanniene vanaf quebracho en mimosa, en hidroliseerbare tanniene vanaf tara, kastaaiinghout en Turksegal is bestudeer. Die gebruik van ‘n enkele analitiese tegniek is nie voldoende om die volledige struktuur van komponente teenwoordig in die ekstrakte te analiseer nie. 13C KMR-spektroskopie en MALDI-TOF-massaspektroskopie is gebruik om die chemiese samestelling en molekulêre massa, onderskeidelik, te bepaal. ‘n Nuwe metode is ontwikkel vir die bepaling van die oligomeer-mikrostruktuur deur gebruik te maak van botsings-geïnduseerde dissosiasie eksperimente. Grootmaat analise het net die gemiddelde samestelling van die ekstrak bepaal. Hidrofiliese-interaksie-vloeistofchromatografie (HILIC) is gebruik vir die analise van gekondenseerde tanniene en gewone fase-vloeistofchromatografie is gebruik vir die hidroliseerbare tanniene. Die HILIC-skeiding is op groter skaal uitgevoer en die fraksies is versamel en gebruik vir MALDI-TOF analise. Hierdie koppeling het getoon dat skeiding plaasvind op grond van molekulêre massa en chemiese samestelling. Grootte-uitsluitingschromatografie is gebruik vir die skeiding van molekules alleenlik op grootte. Hierdeur kon ‘n relatiewe vergelyking van die tannienmolekules gemaak word. Vir die karakterisering van hoë molekulêre massa tanniene is ‘n multi-dimensionele benadering nodig aangesien die verskeie verspreidings teenwoording in hierdie ekstrakte supergeponeerd is.

Wood is our most important renewable resource. We need better quality and quantity both according to the wood itself and the processes that are using wood as a raw material. Hence, the understanding of the chemical composition of the wood is of high importance. Improved and new methods for analyzing wood are important to achieve better knowledge about both refining processes and raw material. The combination of NMR and multivariate analyses (MVA) is a powerful method for these analyses but so far it has been limited mainly to 1D NMR. In this project, we have developed methods for combining 2D NMR and MVA in both wood analysis and metabolomics. This combination was used to compare samples from normal wood and tension wood, and also trees with a down regulation of a pectin responsible gene. Dissolving pulp was also examined using the same combination of 2D-NMR and MVA, together with FT-IR and solid state 13C CP-MAS NMR. Here we focused on the difference between wood type (softwood and hardwood), process type (sulfite and sulfate) and viscosity. These methods confirmed and added knowledge about the dissolving pulp. Also reactivity was compared in relation to morphology of the cellulose and pulp composition. Based on the method and software used in the wood analysis projects, a new method called HSQC-STOCSY was developed. This method is especially suited for assignment of substances in complex mixtures. Peaks in 2D NMR spectra that correlate between different samples are plotted in correlation plots resembling regular NMR spectra. These correlation plots have great potential in identifying individual components in complex mixtures as shown here in a metabolic data set. This method could potentially also be used in other areas such as drug/target analyses, protein dynamics and assignment of wood spectra.

Thesis (MScFor)--University of Stellenbosch, 2007.
ENGLISH ABSTRACT: Unextracted (control) and PHWe Eucalyptus grandis wood chips were pulped at 15% active alkali (AA) and 1% antraquinone (AQ). Another batch of wood chips were then inoculated with fungal co-cultures of Aspergillus flavipes and Pycnoporus sanguineus. FCCi wood chips were incubated for four weeks; one PHWe inoculated experimental treatment was incubated for three weeks. The full pulping cycle (160 min) was used to digest the experimental treatments with the exception of one lot of PHWe wood chips that were pulped for 150 minutes. A further experimental treatment of PHWe wood chips was cooked at a reduced AA charge of 14% and 1% AQ. Analysis of variance (ANOVA) of the data from all the experimental treatments was conducted and the differences within the experimental treatments were determined using Statistica (v7, 1984–2006). The F-value (Fischer distribution) and the p-value as well as a non-parametric test known as the Mann-Whitney procedure was tested at the 95% confidence limit. For a further enhancement of the 95% confidence limit the screened yield data was tested by the Bootstrap method. Scanning electron micrographs clearly demonstrated the changed structure and appearance of the chip cross-sectional area after the different pretreatments. Although the mean average results of all the screened pulp yields showed no significant statistical difference (p> 0.05), differences in screened yield of up to 2.5% were obtained. All the weighted means of the rejects showed a significant difference (p < 0.05). Other pulp properties like shive content, chemical consumption, Kappa number, handsheet brightness and strength tests showed mixed results i.e. rejected or accepted the hypothesis (p> or =or < 0.05). The hypothesis that the combined PHWE and FCCI of wood chips would further increase the pulp yield had to be rejected. It is however anticipated that the combination of PHWE with successive co-culture fungal pretreatment would be very beneficial in obtaining higher pulp yields for fully bleached chemical pulp. Further research would be required to test this assumption. This investigation confirmed the expected beneficial effects of combined PHWE and FCCI pretreatments of wood chips on the strength properties. In addition the combined treatment also improved the initial bonding strength potential of the unbeaten fibres.
AFRIKAANSE OPSOMMING: Onbehandelde en met onder druk, warm water uitgeloogde Eucalyptus grandis houtspaanders is respektiefwelik met 15% aktiewe alkali (AA) en 1% antrakinoon (AQ) verpulp. Hierdie is dan met swamkokulture van Aspergillus flavipes en Pycnoporus sanguineus inokuleer en respektiewelik vir drie en vier weke inkubeer. Onder druk uitgeloogde houtspaanders is ook vir 150 minute verpulp by 15% AA 1% AQ en by ‘n verminderde AA van 14%. Pulpevaluasies is uitgevoer op alle eksperimentele behandelinge. Alle onder druk uitgeloogde en met swamkokultuur inokuleerde houtspaanders het ‘n laer pulpopbrengs, uitskot, skilferinhoud, Kappanommer en ‘n hoër RAA en helderheid opgelewer in vergelyking met die vars houtspaanders. Die vars en warm water uitgeloogde houtspaanders het soortgelyke pulpopbrengs opgelewer. ‘n Variansieanalise (ANOVA) van die data van alle eskperimentele behandelings is uitgevoer gebruikmakende van Statistica (V7, 1984 – 2006). Die F-waarde (Fischer-verspreiding) an die p-waarde so wel as ‘n parametriese toets (Mann-Whitney prosedure) is getoets by ‘n 95% betroubaarheidsgrens. Vir ‘n verdere verhoging van die 95% betroubaarheidsgrens van die pulpopbrengs, is die beskikbare data weer getoets met die Bootstrap-metode. Alle gemiddelde pulpopbrengswaardes het geen beduidende statistiese verkil opgelewer nie (p>0.05), alhoewel verskille van tot 2.5% in pulpopbrengs verkry is. Alle gemiddelde uitskotwaardes het ‘n beduidende verskil getoon (p<0.05). Die ander pulpeienskappe soos skilferinhoud, verbruik aan chemikalieë, Kappagetal, handvel helderheid en sterktewaardes het gemengde resultate opgelewer maw verwerping of aanvaarding van die hipotese p> or =or < 0.05. Die hipotese dat die gekombineerde PHWE en FCCI van die houtspaanders die pulpopbrengs verder sou verhoog moes verwerp word. Daar word egter verwag dat die kombinasie van PHWE met opeenvolgende swamkokultuur behandeling baie voordelig sou wees op die pulpopbrengs van ‘n ten volle gebleikte chemiese pulp. Verdere navorsing is nodig om hierdie veronderstelling te toets. Die ondersoek het die verwagte woordelige effek van die gekombineerde PHWE en FCCI voorbehandelings van die houtspaanders op die papierstrkte-eienskappe bevestig. Bo en behalve dit, het die gekombineerde behandeling ook die aavanklikte bindsterkte potensiaal van die ongeklopte vessels verbeter.

Thesis (PhD(For))--Stellenbosch University, 2014.
ENGLISH ABSTRACT: Pinus patula is the most intensively planted conifer in the tropics and sub‐tropics. In South Africa Pinus patula plantations are the main saw‐log resource for structural lumber production. Improved intensive silvicultural practices and tree breeding have resulted in marked increases in the rate of growth. To reap the financial benefits of the faster growth, plantation managers are more and more inclined to reduce rotation ages, which inevitably results in the production of higher proportions of juvenile wood at final harvest, and lumber which often does not meet the minimum requirements for stiffness for structural lumber. Knowledge of the variation and the accurate prediction of the mechanical properties of the timber of standing trees can have various benefits for growers and processors of trees. It can be used for tree allocation to different processing facilities, for processing production planning, and to assist tree breeders to screen and select for superior breeding material. The objectives of this study were (1), to examine the within‐ and between‐tree variation in wood properties of young South African grown Pinus patula trees known to have important impacts on the suitability of sawn lumber for structural purposes and (2), to develop empirical prediction models for the flexural lumber properties from standing Pinus patula, based on variables that could be assessed non‐destructively from standing trees. Sample material was obtained from 170 trees (16‐20 years old) established in 17 compartments along the Mpumalanga escarpment of South Africa. A large number of variables which could be obtained non‐destructively from the trees while they were still standing, were measured. The trees were subsequently felled and two logs, 2.1 m in length, were extracted from each tree at two height positions. The 340 logs were processed into 1402 pieces of lumber for further measurements and destructive testing. Results showed that the mean modulus of elasticity measured on edge (MOEedge) was far below the limits set for structural grade softwood timber in South Africa. All the desirable properties for structural lumber improved with distance from the pith with the exception of the 5th percentile value for modulus of rupture (MOR), which was higher at the pith than for the boards processed adjacent to the pith. Boards processed from the lower part of the stem were superior in most of the important properties compared to those higher up in the stem. Separate multiple regression models for predicting the average dynamic MOE (MOEdyn) of individual boards, trees and compartments were developed. The models managed to explain 68%, 60% and 95% of the variation in MOEdyn respectively. The models developed for MOR explained 40% and 42% of variability at board and tree level respectively. At compartment level, 80% of the variation in the 5th percentile MOR value could be explained by the model. Sensitivity analyses showed that site index at base age of 10 years, acoustic time‐of‐flight, wood density and ring width were the most influential variables in the MOE models. The models indicated that tree slenderness during early growth seems to play a major role in determining the dynamic MOE and MOR of lumber. This is in agreement with Euler’s buckling theory and the bending stress theory. Microfibril angle (MFA) and density were measured on radial strips taken from a sub‐sample of trees with the Silviscan 3 technology. The mean microfibril angle per year ring in Pinus patula varied between 7o and 29o. In general MFA decreased with distance from the pith and height above ground level. A multiple regression model including microfibril angle, density and ring width explained 71% of the variation in the dynamic MOE of boards. Sensitivity analysis on the model showed that microfibril angle and density had roughly equal influences on predicting the MOEdyn of Pinus patula boards.
AFRIKAANSE OPSOMMING: Pinus patula is die mees aangeplante naaldhoutspesie in die tropiese en sub‐tropiese areas van die wêreld. Dit is die grootste bron van saagblokke vir die produksie van strukturele hout in SA. Intensiewe boskultuurpraktyke en boomteling het gelei tot ‘n merkbare verhoging in die groeitempo van die spesie. Plantasiebestuurders is gevolglik geneig om rotasie‐ouderdomme te verlaag, wat lei tot ‘n groter persentasie jeughout wat nie aan die minimum styfheidvereistes van strukturele hout voldoen nie. Kennis van die variasie en die akkurate voorspelling van die meganiese eienskappe van staande bome kan voordele inhou vir beide die verbouers en verwerkers van bome. Dit kan byvoorbeeld van hulp wees met die toewysing van bome aan verwerkingsfasiliteite, vir produksiebeplanning, en vir ondersteuning met die keuse van teelmateriaal vir boomtelers. Die doelwitte van hierdie studie was (1), om die binne– en tussenboomvariasie in die houteienskappe, wat ‘n bepalende invloed het op die geskiktheid van jong Suid Afrikaanse Pinus patula bome vir strukturele hout produksie, te ondersoek en (2), om empiriese modelle vir die voorspelling van die buigeienskappe van planke te ontwikkel, gebaseer op veranderlikes wat niedestruktief op staande Pinus patula bome ge‐evalueer is. Monsters vir die studie is verkry vanaf 170 bome (16‐20 jaar oud), geplant in 17 vakke op die Mpumalanga platorand van Suid Afrika. ‘n Groot aantal veranderlikes is nie‐destruktief gemeet op die staande bome waarna die bome gevel is en twee saagblokke, 2.1m in lengte, is op twee hoogte posisies uit elke boom verwyder. Die 340 blokke is verwerk tot 1402 planke vir verdere metings en destruktiewe toetse. Resultate het getoon dat die gemiddelde modulus van elastisiteit gemeet op die dwarskant (MOEedge) aansienlik laer was as wat vereis word vir strukturelegraad hout in Suid Afrika. Al die gewenste eienskappe het toegeneem met afstand vanaf die murg behalwe die 5de persentiel breekmodulus (MOR), wat hoër was vir murgplanke as vir aangrensende planke. Planke afkomstig van die laer dele van die stam het oor die algemeen beter eienskappe gehad as planke afkomstig van die hoër dele. Veelvuldige regressiemodelle kon 68%, 60% en 95% van die variasie in die gemiddelde dinamiese MOE (MOEdyn) op die vlak van onderskeidelik individuele planke, bome en vakke verklaar. Die modelle vir MOR kon 40% en 42% van die variasie op onderskeidelik plank‐ en boomvlak verklaar. Die model vir 5de persentiel MOR van vakke kon 80% van die variasie verklaar. ‘n Sensitiwiteitsanalise het aangetoon dat groeiplekindeks op ouderdom 10, akoestiese vlugtyd, digtheid en jaarringwydte die belangrikste veranderlikes was wat MOEdyn beïnvloed het. Die modelle het aangetoon dat die slankheid van bome tydens vroeë groei vermoedelik ‘n belangrike invloed op die MOEdyn en MOR van planke het. Dit is in ooreenstemming met Euler se knikteorie en die buigsterkteteorie. Die mikrofibrilhoek en digtheid van ‘n steekproef van die bome is gemeet met die Silviscan 3 apparaat. Die gemiddelde mikrofibrilhoek per jaarring het tussen 7 o en 29o varieer. Hierdie variasie was hoofsaaklik afhanklik van boomhoogte en aantal jaarringe vanaf die murg. ‘n Veelvuldige regressiemodel wat mikrofibrilhoek, digtheid en jaarringwydte insluit, kon 71% van die variasie in MOEdyn verklaar. ‘n Sensitiwiteitsanalise op die model het aangetoon dat mikrofibrilhoek en digtheid ongeveer ewe belangrik was wat betref hulle invloed op die voorspelde MOEdyn van Pinus patula planke.

The use of wood pellet boilers for residential space heating has significantly increased over the past decade. Wood pellets are a biomass-based renewable energy made by pelletizing debarked wood fiber. Compared to log wood and wood chips, wood pellets have higher energy density, relatively uniform fuel quality, easier to automate their use, and therefore, are being more widely used.

A typical wood pellet heating system has three components: the boiler (energy generation unit), the thermal energy storage (TES) tank (energy storage unit), and the building (energy consumption unit). The three components form into two loops: the boiler to TES tank loop and the TES tank to building loop.

Three modern wood pellet boilers were installed and monitored in this research. Two 25 kW boilers (PB and WPB) were installed in the end of 2014 and a 50 kW boiler (LGB) was installed in March of 2016. PB is used only for radiant floor heating and WPB is used for traditional baseboard/cast iron radiators space heating as well as providing domestic hot water (DHW) supply. LGB boiler is used for concrete slab heating. The three boiler installations provide different methods of heating and different levels of building heat demand.

This research first evaluated the performance of residential scale wood pellet boilers (25 – 50 kW) in terms of boiler operation characteristics, thermal efficiency, boiler emissions, TES tank stratification and discharge efficiency, etc. Comparisons were also made among different boilers and suggestions for improvements were made. A process dynamic simulation using VMGSim was built up based on the field monitoring data. Good agreement between the simulation and field data was found. The model was then used to size the TES tank with respect to different boiler capacities and heating demands. A system sizing algorithm was provided in the end. The results will be used to compose a guidance document for wood pellet boiler heating systems.

This research assessed the influence of hydrologic gradients on woody debris dynamics in a Cumberland Plateau watershed, eastern Kentucky, U.S.A. Although the breakdown of wood can be attributed to several different processes, including leaching, biological decay, fragmentation, and transport, the influence of differing flow regimes has been unstudied. The objectives of this study were to examine how stream channel type (temporary vs. perennial) affected wood processing dynamics (i.e., mass loss and macroinvertebrate colonization and standing stock patterns). Two questions were addressed: (1) do mass loss rates of wood differ across hydrological gradients in stream channels?, and (2) do macroinvertebrate colonization and standing stock patterns vary in relation to hydrologic gradients? Although within each channel type both dry mass and ash free dry mass loss followed a negative exponential model (p < 0.05), there wasn’t a significant between-channel difference in mass loss rates (p > 0.05). Breakdown rates (-k) ranged from 0.133 – 0.194year-1 for perennial streams compared to 0.103 – 0.170year-1 in the temporary streams. Collector-gathers comprised the greatest proportion of macroinvertebrates, accounting for 65.5% (temporary) and 59.3% (perennial) of all taxa colonizing wood bundles, followed by shredders (16.1%, 16.8%), predators (16.8%, 20.1%), (scrapers < 0.1% in both reaches) and filtering collectors (1.2%, 3.7%). Overall, there were no significant between-channel differences for total macroinvertebrate abundance, total macroinvertebrate biomass, and similarly for abundance and biomass of all functional groups. There was a trend, however, of decreasing density and biomass over time of collector-gathers and shredders on wood. Overall, hydrological gradients had no effects on short-term breakdown rates of woody debris or macroinvertebrate colonization patterns. Studies of wood breakdown have been shown to require long study periods (≥ 5 years), therefore, future studies of hydrological gradient may show differing results for woody debris breakdown.

Thesis (MScFor (Forest and Wood Science))--University of Stellenbosch, 2009.
ENGLISH ABSTRACT: Wood waste, when used for gasification is commonly pressed into briquettes, especially if no uniform particle size is available. This densification reduces problems of handling, storage and transportation and improves the combustion performance because of a more uniform fuel size. Briquettes have to be mechanically strong enough to be handled. Cohesive strength is provided by residual moisture and lignin present in the wood. The lignin acts as a natural binder. However, the briquetting process becomes more complicated if one wants to add other agricultural waste products that do not necessarily contain lignin as binders,, In this study we have investigated various briquetting process parameters, such as mixing ratios of briquettes containing wood chips, grape skins and chicken litter, moisture content and press time. The aim was to determine the optimum process parameters that allow the production of briquettes, containing a blend of biomaterials that are mechanically stable to allow further handling but yield high energy content at the same time.
AFRIKAANSE OPSOMMING: Wanneer houtafval vir vergassing gebruik word en die partikelgrootte daarvan varieer, word die materiaal normaalweg in ’n brikket gedruk. Brikketvorming vergemaklik opberging, hantering en vervoer. Weens die meer uniforme grootte en vorm van die brikkette is verbranding daarvan heelwat meer doeltreffend. Brikkette moet egter meganies sterk genoeg wees om hanteer te kan word. Die kohesiewe sterkte word deur residuele vog en lignien, wat as natuurlike bindmiddel in hout aanwesig is, verskaf. Indien ander materiale soos landbouafval, wat noodwendig geen lignien bevat nie egter gebruik word, word die brikketvormingsproses meer kompleks. In hierdie ondersoek is verskeie brikketvormingsparameters evalueer. Mengverhoudings van brikkette wat houtspaanders, druiwedoppe en hoendermis bevat, asook invloed van materiaalvoggehalte en druktyd is bestudeer. Die doel was om die optimale materiaal- en prosesparameters vas te stel wanneer ’n mengsel van biomateriale gebruik word om brikkette te lewer wat meganies sterk genoeg is maar steeds die hoogste energieopbrengs lewer.
Centre for Renewable and Sustainable Energy Studies

Wood is a natural raw material, and would hardly be considered a risk to the environment. However, the handling of wood materials on an industrial scale has been shown to have a negative impact on water bodies that run-off from industrial sites that process wood-based materials. Most investigations related to water pollution from wood-based industries have focused on large industrial sites such as pulp and paper mills. The goal of the present thesisis to understand better such environmental problems and treatment solutions that occur at most wood handling sites. Where there are large outdoor storage areas for logs and sawdust that are exposed to rainfall or irrigation, such as the wooden-floor and bio-energy sectors. Leachate generated by the contact of water with wood in storage areas contains a large amount of organic matter that is potentially hazardous to water bodies that receive run-off from the site. It has been found that different wood species yield different leachate compositions, with leachate from oak having the highest pollutants content, followed by leachate from pine. This investigation shows that oak has the potential to leach about 10 times the amount of polyphenols compared with other investigated species (i.e., pine, beech and maple). Furthermore, oak leachates have the lowest ratio of biological oxygen demand at 7 days tochemical oxygen demand (0.12), which suggests a potential problem with the biological degradation of this leachate. It has also been shown that leachate from wood are potentially toxic to aquatic organisms. Treatability studies with the aim of reducing the environmental impact of wood leachate were conducted on a pilot scale as part of the scope of this thesis. The results showed, among other options, the possibility of using constructed wetlands to treat leachate. It was found that plants and aeration can affect the performance of a wetland. However, the most important factor is the time water spends in the wetland. Filter material that could be used to absorb leachate was also studied. A filter consisting of a mixture of peat and ash (from incinerated organic matter), was used to absorb a specific chemical group (polyphenols) in the leachate. It was also shown that polyphenols are vulnerable to ozone, representing a third viable treatment process.
Trä är ett naturligt råmaterial som knappast anses vara en risk för miljön. Däremot har hanteringen av trämaterial i industriell skala visat sig ha negativ inverkan på vattendrag. De flesta utredningar avseende vattenföroreningar inom träbaserade industrier har fokuserat på stora industrier med stor vattenförbrukning så som massa- och pappersbruk. Lakvatten som alstras vid kontakten mellan vatten och trä innehåller höga halter av organiska ämnen som är potentiellt farliga för vattendrag. Målet med denna avhandling är att få kunskap om ovanstående miljöproblem och möjlig behandlingar av dessa. Förorenat lakvatten skapas av industrier, där stora mängder timmer och sågspån är placerade utomhus och utsätts för regn och bevattning, såsom inom trägolv och bioenergisektorn. Man har funnit att lakning från olika träslag ger olika sammansättningar på lakvattnet, där lakvatten från ek har den högsta halten av föroreningar följt av furu. Denna undersökning visar att ek har potential att laka ut tio gånger så mycket polyfenoler jämfört med andra undersökta arter (tall, bok och lönn). Dessutom har lakvatten från ek den lägsta andelen av biologisk syreförbrukning efter 7dagar per kemisk syreförbrukning (0,12), vilket tyder på ett potentiellt problem med den biologiska nedbrytningen av detta lakvatten. Man har även påvisat att lakvattnet från trä är potentiellt giftigt för akvatiska organismer. Studier för att försöka minska miljöpåverkan av lakvatten från denna trädsort gjordes i pilotskala inom ramen för denna avhandling. Dessa studier visade bland annat på möjligheterna att använda sig av våtmarker som reningsmetod, där växter och luftning påverkar hur bra en våtmark fungerar. Men den viktigaste faktorn var den ökade uppehållstiden som vattnet får i våtmarken. Utöver studier av våtmarker har också ett filtermaterial studerats, filtret bestod av en blandning av torv och aska, som användes för att absorbera en specifik kemisk grupp i lakvattnet (polyfenoler). I en tredje typ av behandlingsprocess visade det sig också att polyfenoler effektivt kan brytas ned av ozon.

Introduction: Throughout many parts of the world, forests exist in one form or another. And for the timber from these forests to be used, it must be processed by, for example, sawing into planks and dried. Studies have shown that profits for the forest owners increase from beneficial processing of these raw materials. An efficient use of this raw material is to process it into lightweight panels. Some general incentives for using lightweight constructions are: economical, technical and environmental. Some general weaknesses with sandwich constructions are more sensitive to impact and bumps, risk for delamination, harder to make fastenings, and more sensitive to the concentration of point loads. This work aims to increase the knowledge of properties and design of wood based lightweight panels used for interiors and furniture. The intention with this knowledge is that it can contribute to the development of lightweight panels. Material and method: A lightweight panel of cross glued sandwich type and a cross-glued multi-layered panel with densified face sheets have been used as an example to investigate and understand which parameters are crucial for a lightweight panel, made of wood. The lightweight panel of sandwich construction has been studied to consider the changes of shape brought about by moisture, as well as which mechanical properties this panel has, with a focus on creep deformation. Two methods for reducing the moisture-generated shape changes so as to increase the shape stability of the panel have also been studied. The methods are crossgluing and thermal treatment of the wood material. In the investigations of the panels, primarily quantitative methods in the form of empirical tests have been used. Some numerical simulations describing the moisture-generated shape changes and stresses that arise in the investigated lightweight panels were also made. Results and discussion: Cross-gluing of a multi-layered panel and also for the lightweight panel used in this study is a way to reduce the movement in the panel, generated by moisture. The drawbacks with this method are that stresses occur in the panels when the moisture change, and this can lead to a decrease in the shape stability of the panel. Thermal treatment can also be used to decrease the moisture-generated movement in wood, and in this way increase the shape stability of the product. In those cases where the empirical experiments were combined with numerical simulations, there was good agreement between the experimental and the numerical results. With the lightweight panels a weight reduction was achieved from 307 to 540 kg/m3 compared with a solid beech wood panel. The creep deformation of the lightweight panel was better or comparable for 6 of the 8 studied groups, compared to solid beech wood panel. The study also show that is possible to adapt the mechanical properties through its design of this lightweight panel.

Denna avhandling behandlar den svenska trähusbranschens behov och möjligheter att erhålla trämaterial med egenskaper som uppfyller de krav som produktion och slutkund ställer. Ett gemensamt problem för den svenska trähusbranschen är de kvalitetsbrister hos det virke sombranschens företag köper för sin produktion, som kan resultera i merkostnader för branschen med 100 MSEK årligen. Trähusföretagen uttrycker en viss uppgivenhet över bemötandet från virkesleverantörerna. Virkesleverantörerna å sin sida menar att köparna av trämaterial inklusive företagen i trähusbranschen i ringa utsträckning genomför reklamationer. Avgörande för genomförda virkesaffärer är ofta priset – det blir affär med den som erbjuder lägst pris. Sammantaget innebär detta att det inte blir någon dialog mellan leverantör och köpare som utvecklar synsättet på trämaterialkvalitet. Avhandlingsarbetet har bland annat behandlat beredning av träråvaran till färdiga ämnen t.ex. studier vid tillverkning av kvistfria ämnen. Resultatet av arbetet visar på vikten av att genomföra utvärderingar av material och leverantörer. Resultatet visar vidare att kapkostnaden för färdiga träämnen inkl. spill är ca 1/3 av ämneskostnaden. Dock är kostnaden för trämaterialet låg i relation till totalkostnaden för det färdiga huset vilket innebär att ett högre pris för ett virke som fullt ut motsvarar kravspecifikationerna i liten utsträckning påverkar totalkostnaden för huset. Råd till trähusbranschen är att ställa krav på virkesråvaran, utvärdera material och leverantörer samt att trähusbranschen ska sikta mot att bli en modern tillverkningsindustri i likhet med de mest framgångsrika inom verkstadsindustrin.
This thesis investigates the needs and opportunities for the Swedish wood house industry to obtain wood material with properties meeting demands of both producers and final customers. A common problem within the Swedish wood house industries is the insufficient quality of the wood material that companies purchase for their production. These flaws in quality can render an additional annual cost for the industry of approximately 10 million Euros. Wood house companies express a certain resignation regarding communication with wood material suppliers. However, timber suppliers claim that they rather receive very few complaints regarding timber quality from wood house companies and other purchasers. For a timber supplier, being able to offer an acceptable price is often a determining factor, since most deals will go to the supplier offering the lowest price. This has led to a non-existent dialogue between suppliers and purchasers regarding how to approach the wood quality issue. This study has, among other things, studied the preparation of sawn wood into finished components, for instance, the production of knotfree boards. The results illustrate the importance of carrying out evaluations of raw material and suppliers. Furthermore, results show that the cutting cost for wood components, including waste is approximately 1/3 of the total cost for ready-made components. However, in relation to the total cost of the house the timber cost is low. This means that a higher price for wood that fully meets the target specifications, will have limited impact on the total cost for the house. The wood house industry is recommended to present firm demands for a high-quality material and to evaluate material and suppliers. In addition to this, the wood house industry should aim towards becoming a modern manufacturing industry, like those most successful manufacturing industries in other fields.

Timber with its natural appearance and glass with its transparency may be appealing material for architects and users of modern buildings. Glass is a brittle material, but it is about six times stiffer than timber. Combined appropriately, the materials could form different types of composite products, e.g. beams or shear walls, that can be included in the load-carrying structure of buildings. e knowledge on load- carrying timber/glass components is limited. e intention of this research has been to contribute to the knowledge required for the industry to be willing to produce timber/glass components for the market. The thesis includes experimental testing accompanied with complementary nite element simulations, which provide more details and information about the test results. Tests were performed on small-scale specimens with a bond area of 800 mm2 as well as on I-beam and shear wall prototypes. For the small-scale specimens tested in standard climate, three different adhesives were used for the bond line between timber and glass. ese specimens were tested in both tension and shear. In addition, one of the adhesives was used for small-scale shear specimens which were exposed to different humidity levels before the tests were performed. e 4 m long I-beam prototypes designed with a web of glass and wooden anges were tested in four- point bending. e shear wall prototypes were tested by applying either a vertical load, a horizontal load or a combination of these, all being applied in the plane of the shear wall. Of the three adhesives used in the small-scale testing, an acrylate adhesive had the largest strength, both in tension and in shear. e study on the effect of humidity was performed with this adhesive. is study indicates that the adhesive properties do not change dramatically in indoor climate. is adhesive was also used for twelve of the fourteen tested I-beams. e results from the beams show that a signi cant redundancy is obtained; the load at the nal failure was around 240 % of the load when the rst crack in the glass web appeared. e shear walls were glued using the acrylate adhesive and for a few cases a 2-component silicone based adhesive. e results from the shear wall tests showed the shear wall to behave in a much more brittle manner, without any noticeable redundancy.

The objective of this study was to investigate the effects of weathering on the performance of intumescent fire-retardant coatings on wooden products. The weathering effects included primary (solar irradiation, moisture, and temperature) and secondary (environmental contaminants) parameters at various time intervals.

Wildland urban interface (WUI) fires have been an increasing threat to lives and properties. Existing solutions to mitigate the damages caused by WUI fires include protecting the structures from ignition and minimizing the fire spread from one structure to another. These solutions can be divided into two general categories: active fire protection systems and passive fire protection systems. Passive systems are either using pre-applied wetting agents (water, gel, or foam) or adding an extra layer (composite wraps or coatings). Fire-retardant coating treatment methods can be divided into impregnated (penetrant) and intumescent categories. Intumescent coatings are easy to apply, economical, and have a better appearance in comparison to other passive fire protection methods, and are the main focus of this study.

There have been limited studies conducted on the application of intumescent coatings on wooden structures and their performance after long-term weathering exposure. The main concerns of weathering effects are: 1) the reduction of ignition resistance of the coating layer after weathering; and 2) the fire properties of coatings after weathering since coatings might contribute as a combustible fuel and assist the fire growth after ignition.

Three intumescent coatings were selected and exposed to natural weathering conditions in three different time intervals. Two types of tests were performed on the specimens: a combustibility test consisted of a bench-scale performance evaluation using a Cone Calorimeter, and a thermal decomposition test using Simultaneous Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) method (also known as SDT). For each coating type and weathering period, three different radiative heat flux levels were used in the combustibility tests. Data obtained from the tests, including flammability and thermal properties, were gathered, analyzed, and compared to non-weathered specimens.

The results revealed visible effects of weathering on pre (and up to)-ignition flammability and intumescent properties, especially decreases in Time-to-Ignition (TTI), Time-to-Intumescence (t_intu.), and (maximum) Intumescence Height (H_intu.) values in weathered specimens. These results showed that the ignition resistance of the coating layers decreased after weathering exposure. On the other hand, the obtained results from weathered specimens for the post-ignition flammability properties, especially Peak Heat Release Rate (PHRR) and Effective Heat of Combustion (EHC) did not show a significant difference in comparison to the non-weathered samples. These results demonstrated that the weathered coating layer would not likely to act as an additional combustible fuel to increase fire spread.

Thesis (PhD (Forest and Wood Science))--Stellenbosch University, 2007.
ENGLISH ABSTRACT: There has been a reported reduction in the durability of creosote treated, wooden utility poles in South Africa in recent years. Several factors could have been responsible for this. In this study, Eucalyptus grandis pole drying schedules currently used, methods of measurement of moisture content (MC) after drying and drying defects were investigated. Relationships involving drying defects and MC gradient before treatment which may help in the development of simple nondestructive methods of assessing defects such as surface checking, honeycomb and collapse, and MC gradient were also explored. The long term goal of this study was to increase the durability of treated poles by avoiding unacceptable drying defects and MC values before treatment. The results of this investigation are presented in the following chapters: an introduction motivating the aims of the investigations (Chapter 1); a review of literature relevant to MC and drying defects in sawn or round wood (Chapter 2); ready for press manuscripts on MC and drying defects in kiln-dried E. grandis poles (Chapters 3 to 7) and a general conclusion that links up chapters 3 to 7, and recommendations (Chapter 8). The auger drill method gave reliable MC values when samples in increments of 25 mm depths into the pole were taken. However, when single samples of 50 mm and 75 mm depths were considered, the auger drill MC measurements were unreliable. It was concluded that SABS SM 983 (2000), which specifies taking single radial auger drill samples of depth 70±5 mm at pole mid length, is not a reliable method of measuring MC in a kiln-dried E. grandis pole. Correlation results indicated that tree growth factors such as sapwood depth, green MC and heartwood percentage were related to final drying defects and may be used as criteria for pole sorting before kiln drying. Also, the number of valleys per unit length (VPUL) of the circumference at the theoretical ground line (TGL) was positively correlated with honeycomb and closed surface checks, implying that VPUL as a parameter of the pole circumference profile can be used to assess invisible, internal defects. The dry bulb temperature (Tdb) of 80oC, used to dry poles in industry, was too high and resulted into unacceptable levels of drying defects in kiln dried E. grandis poles. In addition, the drying period of 8 days was too short to attain an acceptable MC gradient in poles. It is, therefore, recommended that: To use the auger drill method to reliably determine the moisture content of a pole, samples in increments of 25 mm should be taken. MC measurements should be made at the most critical zones of a pole such as the TGL and not higher up since there is normally considerable MC variation in the longitudinal direction. It is also important to consider sampling more than one position on the pole circumference to cater for the MC variation in the tangential direction. For poles with large sapwood depths i.e. >15mm, mild drying conditions at the beginning of a drying run should be used, since such poles may be more susceptible to surface checking. Poles with large heartwood percentages should also be dried with suitable kiln schedules, i.e. with low Tdb to minimise honeycomb and collapse. In general, Tdb lower than 80oC should be considered in order to reduce the defects to acceptable levels. Poles should be dried for longer than 8 days even at Tdb as high as 80oC to reduce the MC to acceptable values and gradients. Since only three schedules were tested, more drying schedules should be investigated to make reliable conclusions about the effect of schedule on drying defects. In addition, more poles per schedule should be considered in order to obtain statistically reliable results. The relationship of pole diameter and drying defects also requires further investigation. Since a limited sample was used to test for the effect of source of poles and drying schedules on defect correlations, further studies should be done on sufficient samples to come up with more reliable conclusions. It is also necessary to further investigate the possible variation in correlation of VPUL and internal defects on a large sample of poles from specific sources and drying schedules.
AFRIKAANSE OPSOMMING: Die afgelope paar jaar is waargeneem dat kreosootbehandelde transmissiepale 'n afname in duursaamheid toon. Verskeie faktore kan hiervoor verantwoordelik wees. In hierdie studie is huidige Eucalyptus grandis oonddrogingskedules en voggehalte- (VG) bepalingsmetodes vóór en na droging asook drogingsdefekte ondersoek. Verwantskappe tussen drogingsdefekte en VG-gradiënt vóór behandeling wat kan meehelp om nie-destruktiewe metodes te ontwikkel om defekte soos oppervlaktekrake, interne barste en instorting en VG-gradiënt te bepaal, is ook bestudeer. Die langtermyn doelwit van hierdie studie is om die duursaamheid van behandelde pale te verbeter deur onaanvaarbare drogingsdefekte en voggehaltes vóór behandeling te vermy. Die resultate van hierdie ondersoek word in die volgende hoofstukke bespreek: 'n inleiding waarin die doelwitte van die onderskeie ondersoeke motiveer word (Hoofstuk 1); 'n oorsig van die literatuur relevant tot VG en drogingsdefekte in gesaagde en rondehout (Hoofstuk 2); persklaar manuskripte oor VG en drogingsdefekte in oondgedroogde E. grandis pale (Hoofstukke 3 tot 7) en 'n algemene gevolgtrekking wat bevindings uit hoofstukke 3 tot 7 saamvat gevolg deur aanbevelings (Hoofstuk 8). Die augerboor-metode kon betroubare VG-waardes lewer indien monsters van 25mm diepteinkremente in die paal geneem is. Augerboor-voggehaltemetings met enkel 50mm en 75mm monsters was egter onbetroubaar. Daar is bevind dat SABS SM 983 (2000), wat 'n enkel radiale augerboormonster tot op 'n diepte van 70±5 mm in die middel van die lengte van die paal spesifiseer, nie 'n betroubare VG-bepalingsmetode vir oondgedroogde E. grandis pale is nie. Die resultate het aangetoon dat boomgroeifaktore soos spinthoutdiepte, groen voggehalte en die persentasie kernhout aan drogingsdefekte verwant is en as basis vir sortering van pale vóór oonddroging gebruik kan word. Ook kon die aantal valleie per eenheidslengte (e. VPUL) van die omtrek by die teoretiese grondlyn (TGL) positief met interne barste en geslote oppervlaktekrake korreleer word wat impliseer dat VPUL as parameter van die omtrekprofiel van die paal gebruik kan word om onsigbare, interne defekte mee vas te stel. Die droëbaltemperatuur (Tdb) van 80oC wat in die industrie gebruik word, was te hoog omdat dit onaanvaarbare vlakke van drogingsdefekte in oondgedroogde E. grandis veroorsaak het. Daarbenewens was die drogingsperiode van 8 dae by 'n Tdb van 80oC te kort om 'n aanvaarbare VG-gradiënt te lewer. Die volgende word derhalwe aanbeveel: Om betroubare VG-resultate d.m.v. die augerboormetode te verkry, behoort monsters in inkremente van 25mm geneem te word. VG-metings behoort in die mees kritiese dele van 'n paal gedoen te word byv. by TGL en nie hoër nie omdat daar normaalweg beduidende VG-variasie in die longitudinale rigting is. Dis ook belangrik om op meer as een posisie op die omtrek te meet om vir die variasie in die tangensiale rigting voorsiening te maak. Ligte drogingstoestande behoort aan die begin van die drogingsproses by pale met groot spinthoutdieptes, bv. > 15mm, gebruik te word omdat sulke pale meer geneigd tot oppervlaktekrake is. Pale met hoë kernhoutpersentasies moet ook met geskikte drogingskedules, bv. met lae Tdb, gedroog word om interne barste en ineenstorting te verminder. Oor die algemeen behoort Tdb laer as 80oC oorweeg te word om die omvang van defekte by aanvaarbare vlakke te hou. Selfs by Tdb so hoog as 80oC behoort pale langer as 8 dae te droog om die VG tot by aanvaarbare waardes en 'n gradiënt te bring. Omdat slegs drie skedules evalueer is, behoort meer skedules ondersoek word om betroubare gevolgtrekkings oor die effek van skedule op drogingsdefekte te verskaf. Addisioneel behoort meer pale per skedule oorweeg word om statisties betroubare resultate te verkry. Die verwantskap tussen paaldeursnee en drogingsdefekte benodig ook verdere ondersoek. Aangesien 'n beperkte aantal pale gebruik is om die herkoms en drogingskedule met defekte te korreleer, behoort verdere studie op genoeg pale gedoen te word om meer betroubare gevolgtrekkings te kry. Dit is ook noodsaaklik om die moontlike variasie in die korrelasie tussen VPUL en interne defekte op 'n groot aantal pale van spesifieke herkoms en drogingskedules vas te stel.

Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 41-46).
Biomorphic silicon carbide, a porous, light and high strength ceramic typically derived from natural wood, has great potential in high temperature and structural applications. Over the past several years, researchers have developed three main routes to fabricating biomorphic SiC: reactive infiltration of molten Si, chemical vapor infiltration of Si or SiO, and SiO₂-bearing solution infiltration. In this study, the latter was investigated and optimized. In addition, a novel synthesis technique, Si suspension infiltration, is proposed that overcomes the major issues present in the current methods. Four wood species (balsa, pine, maple and oak) offering a wide range of porosities were infiltrated with colloidal SiO₂ under varying pressure conditions, and the corresponding weight gains were recorded and studied. The samples were then fired at 1600 °C for 2h under argon flow, and examined via X-ray diffraction (XRD), scanning electron microscopy (SEM) and compression testing. It was found that applying pressure or vacuum produced more effective SiO₂ weight gains. Pine showed superior absorption to other types with its maximum obtained value achieved under vacuum followed by pressure. The starting concentration of SiO₂ solution proved to be crucial in controlling the final mechanical properties of the specimens. XRD analysis revealed that the resulting samples consisted of nearly pure SiC, and SEM images indicated that the initial structure of wood was retained. Due to the nature of the reactions involved with using SiO₂ as a-precursor, the produced specimens tend to be mechanically weak. The new synthesis approach involves the use of <10 pm sized particles of Si instead of nano-sized SiO₂ particles. Pine was selected to serve as the template for absorption, and after two infiltration treatments, the sample absorbed 55.6% of its weight, ~4% higher than its theoretical stoichiometric need, 51.3%. EDS analysis revealed that Si was able to spread homogenously, and XRD spectra confirmed the material identity to be composed of mainly pure SiC with minor trace metal contamination. Compression testing illustrated better mechanical properties of the Si prepared specimen, suggesting the potential of this method to replace existing techniques.
by Abdullah Yousef Alsalloum.
S.B.

Thesis (M.S.F.S.) PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.
The ability to extract ignitable liquids from wooden fire debris samples is an important aspect of arson investigation. A common method by which the ignitable liquids are extracted is heated passive headspace extraction, a process by which a sample is heated in a sealed container and any ignitable liquid residues present desorb from the sample and adsorb to an adsorbent present in the container. An activated charcoal strip is most often used as the adsorbent, and the recommended extraction procedure is to allow the sample to extract in an oven set at a temperature between 50 °C and 80 °C for an amount of time between 8 and 24 hours. The ignitable liquid residues can then be eluted from the adsorbent and analyzed by gas chromatography-mass spectrometry (GC-MS) to identify the type of ignitable liquid present within the sample as well as specific compounds within the ignitable liquid. The extraction procedure typically does not yield 100% of the original amount of ignitable liquid deposited on the sample. Some of the ignitable liquid residue loss can be attributed to any irreversible adsorption that occurs between the substrate and the ignitable liquid. This irreversible adsorption is not known to be a constant across different wood genera; however, the extent of irreversible adsorption may vary between differing genera of wood. The focuses of this thesis are to examine any trends in irreversible adsorption that occur in wooden substrates, to see which genera of wood presents the greatest retention of ignitable liquids, and to see if any correlation exists between the retention capabilities of a wood genus and its density. The densities were determined for a total of thirteen common wood genera, which were spiked with one of three ignitable liquids and then subjected to heated passive headspace extraction. A semi-quantitative approach was taken by comparing the abundance of specific compounds within an ignitable liquid extracted from a wood substrate to the abundance present in a diluted sample of the same ignitable liquid, allowing a comparison between different genera to be made. Ultimately, it was determined that different genera of wood do display different retention capabilities for the common ignitable liquids examined in this thesis, but there was no genus of wood which consistently demonstrated a greater retention for the ignitable liquids compared to the other genera, nor was there a genus of wood which consistently allowed for greater recovery of the ignitable liquids compared to the other genera.
2031-01-01

The research described here provides the technology and theory to quantify surface quality for a variety of wood and wood-based products. This technology provides a means of monitoring trends in surface quality which can be used to discriminate between Agood@ products and Abad@ products (the methods described in this research are not intended to provide ?grading? of individual workpieces) as well as provide information to the machine operator as to the source of poor quality machined surfaces. The analysis can be done either on-line at industrial speeds or off-line as a periodic quality control tool. Although the surface quality can be quantifiably measured, the determination of the best feature from the surface profile (root mean square, peak amplitude, average wavelength, frequency content, Joint Time and Frequency Analysis (JTFA) and Wavelet Analysis results, etc.) for the quantification of surface Adefects@ is highly dependent on the application. This research consisted of three broad areas: (1) determination of an optimal hardware configuration for both laboratory and industrial surface scans of wood products, (2) determination of the optimal set of surface descriptors as well as the development of advanced signal processing techniques such as the wavelet transform to accurately describe the quality of a surface as well as provide information to the machine operator on the cause of the loss of surface quality, and (3) development of a software interface to distill the advanced signal processing techniques into a readily obtainable and readable format for the machine operator as well as provide assistance for process decisions.

Structure-property relationships of cellulose-based materials including paper, micro- and nano-fiber composites are often strongly influenced by environmental variables. The interaction of polymeric and crystalline structure in cellulose bio-based materials is of high technological importance. Therefore, understanding the underlying mechanism of environmental/material interactions is crucial for engineering products from bio-based materials. This study was undertaken in an effort to develop a technique for the assessment of dimensional stability of cellulose microfibrils as a function of different relative humidity. Analysis of atomic force microscopy images showed that the local dimensional properties of cellulose microfibrils are highly responsive to variable relative humidity, and their hygro-expansive behavior depends on the relative humidity history, and their method of preparation. The results obtained suggested that dimensional and hygro-expansive behaviors of cellulose microfibrils are related to their ultra-structural arrangements and their origin, either directly or indirectly. These findings, hopefully, will prompt an open discussion regarding the dynamic interactions between cellulose and water molecules at a nano-scale.

Low temperature pyrolysis offers a feasible option for wood waste management and the recovery of a variety of useful chemicals. The effect of Chromated Copper Arsenate (CCA) wood preservatives on the yield and composition of various pyrolysis products was investigated in the present research. A novel quantitative 31P NMR methodology has been developed to quantify levoglucosan and levoglucosenone from the pyrolysate of CCA-treated and untreated wood. The CCA treatment on wood had a significant effect on the amount of main carbohydrate derived degradation products of tar. In particular, a higher yield of levoglucosan can be obtained compared to that from untreated wood. Phosphoric acid has proven to be an efficient catalyst to favor levoglucosenone formation. The pyrolysis of CCA-treated wood in the presence of phosphoric acid gave rise to high yields of levoglucosenone, which demonstrated the potential for a new pathway in the rational use of CCA-treated wood waste. Pretreated wood with metal compounds has demonstrated that K2Cr2O7 and CuSO4 salts promote the formation of levoglucosan. The CrO3 treatment was found to favor the formation of levoglucosenone. A kinetic study of the pyrolysis of CCA-treated wood by thermogravimetric analysis has shown that CCA components have a significant influence on the thermal decomposition behavior of CCA-treated wood, which accelerate the weight loss of wood and the oxidation of the char.

The objective of this research is to understand the interfacial behavior of cellulase enzymes and its effect on cellulose hydrolysis. This research began with an in-situ monitoring of cellulose hydrolysis using a piezoelectric based quartz crystal microbalance. The time-course kinetics was modeled using a dose response model. The adsorption indicated by the frequency drop followed a Langmuir model as cellulase enzyme increased. Another important part of this research is the development of a new cellulase activity assay based on the piezoelectric technique. This assay provides an easier and more user friendly method for cellulase enzyme activity measurement. It also helps to clarify an element of the interpretation of frequency drops after the injection of cellulase solutions in the hydrolysis of cellulose film, which has been neglected in previous research. Interfacial adsorption of cellulase protein was also investigated using the depletion method. The effects of substrate properties, primarily the crystallinity, which was characterized using X-ray diffraction, were investigated. The effect of surface area, which was measured using both laser light scattering and BET adsorption, on cellulase adsorption were also investigated. It was found that crystallinity played a more important role in cellulase adsorption than surface areas of cellulosic substrate. In characterization of cellulosic substrates, the water retention value (WRV) was also investigated. The results indicated that lower crystallintiy substrates have higher water retention ability. The cellulase adsorption, as well as desorption, was also studied by using sodium dodecyle sulphate polyacrylamide gel electrophoresis (SDS-PAGE). The adsorption results followed the same trend as indicated by the depletion methods. The various isozymes demonstrated a uniform adsorption in proportion to their concentrations. Desorption appeared uniform. Higher pH was found to create higher desorption for a particular cellulase from a particular substrates. It was also found that cellulase from Trichoderma reesei had higher affinity to cellulosic substrates used in this work than the one from Aspergillus niger.

The objective of this research is to understand the drying behavior of cellulose fibers characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). A parameter termed ?hard-to-remove (HR) water content? was defined as the ratio of water mass to fiber mass at the transition between the constant and falling rate drying zones of an isothermal TGA experiment. The HR water content showed a linear relationship with water retention value. TGA and DSC were used to explain the linear relationship. During drying, free water was observed to evaporate first, followed by trapped water, freezing bound water and then non-freezing bound water, with some overlap. Trapped water can be described as water bound to the fibers, but difficult to evaporate. For pilot papermachine samples, all the water in the wet web entering the dryer section was HR water, with no free water detected. Based on the results, a qualitative drying model of cellulose fibers was proposed with regard to decreasing moisture ratio. Changes in the pore size distribution during drying were determined using DSC measurements and the Gibbs-Thomson equation. Larger pores collapsed first followed by the sequential collapse of smaller pores, indicating that pore wall collapse resistance is critical. The average pore size for bleached softwood was calculated to be about 80 nm and decreased with drying. A constant pore size of about 20 nm was observed at moisture ratios below 0.3 g/g, which corresponds to one-to-two layers of non-freezing bound water. The heat of vaporization of water associated with cellulose fibers was determined using modulated DSC and showed a steep increase at moisture ratios below 0.3 g/g, indicating that a higher energy is required to evaporate non-freezing bound water.

Lignin, the glue that keeps fibers together, is a complex three dimensional network polymer which has shown association phenomena in solution. Following the molecular weight of the biopolymer in solution as a function of time allow us to explore their observable de-association phenomena. These measurements were carried out using multiple angle light scattering (MALS) photometry in the static mode. EMAL (Enzymatic Mild Acidolysis Lignin) from hardwood and softwood were isolated and an additional method for the complete dissolution of such biopolymers in THF was further developed. Once the challenge of the measurement procedures were worked out, some rather accurate dn/dC values for lignin solutions were obtained as a function of time. This effort when coupled to additional work using static light scattering measurements (Zimm plots) for the same solutions offered an insight into the self-assembly processes operating within the lignin biopolymer.

Polyampholytes are polymers that have both positively and negatively charged groups in the same chain. In recent years polyampholytes have started to be used in papermaking applications, as well as in sludge treatment processes. Benefits, in the case of papermaking, have included increased dry-strength and faster removal of water. But the molecular mechanisms by which such benefits are achieved have not been fully understood. This thesis project focused on effects related to polyampholyte charge density. A series of polyampholytes with a fixed charge ratio but different charge density was used for the experiments. Analysis methods included pH titrations, streaming current titrations, and adsorption isotherms. From pH titrations the charge density of cationic and anionic groups under different pH were calculated. From streaming current tests the net apparent charge density under different pH was calculated. And from adsorption tests it was found that the highest adsorbed amounts were achieved in certain cases corresponding to the highest content of ionic groups on the polyampholytes. Adsorption depended strongly on pH. Substantial differences were observed when comparing results obtained with polyampholyte samples versus ordinary polyelectrolyte samples with same charge density of cationic or anionic groups.

Over the years, hydrogen peroxide has been used to improve the brightness of pulp at the end of a bleaching sequence. However, the degree of delignification achieved by a hydrogen peroxide stage is usually modest. That is because in alkaline condition the hydroperoxy anion reacts with chromophores in pulp as a nucleophile that does not oxidize residual lignin to a significant extent. In order to enhance the reactivity of hydrogen peroxide as an oxidant, a binuclear manganese complex Mn(IV)2-Me4DTNE was added. As a result, the degree of delignification was significantly improved, while at the same time, the strength properties of the pulp were better preserved compared traditional in hydrogen peroxide delignification. In order to better understand the mechanism of this delignification process, lignin model compound oxidation and kinetics of pulp delignification were studied. In addition, residual lignin was isolated from the pulp before and after delignification and then characterized by GPC, FTIR, and 1H-13C 2D NMR. Shown by the model compound study, hydrogen peroxide is able to oxidize 1-(3,4-dimethoxyphenyl)ethanol, E-diphenylethene, and 1-(3,4-dimethoxyphenyl)-1-propene to a considerable extent when catalyzed by Mn(IV)2-Me4DTNE, indicating that the reactivity of hydrogen peroxide as an oxidant is significantly improved. Indeed, as shown by the kinetic study of pulp delignification, the degree of delignification as well as the rate of delignification were greatly improved when the catalyst was applied. In addition, the catalyzed delignification process benefits from the concerted reaction mechanism that regulates the formation of hydroxyl radicals responsible for the severe damage to the fibers. As a result, the strength properties were well preserved. Shown by the characterization of residual lignin before and after the delignification, residual lignin was oxidized to a good extent which accounts for the significant degree of delignification. The process simulation of this catalyzed delignification process by WinGEMS4.0 showed that this process was profitable if the cost of the catalyst was kept below $330/kg.

The purpose of this research was to study the effect of pretreatment on the extractive content and bleachability of extended delignified kraft pulps. The studies were carried out on both southern hardwood and southern softwood species. It was found that the extractives affected the bleachability of pulps by reaction and blocking mechanisms. For hardwood pulps, the reaction of extractives with bleaching chemicals was more significant. For softwood, the blocking effect of extractives was more pronounced. During the batch extended delignification process, the extractives were accumulated and precipitated on the pulps due to the black liquor recycling. The amount of precipitates was determined by the pretreatment conditions. It was possible to lower the extractive content of both the softwood and hardwood pulps by introducing a gas-off process in the pretreatment stage of a batch extended delignification process. The removal efficiency of extractives was affected by the gas-off process and the extractive distribution. The amount of extractives that was removed by the gas-off process was affected by the pretreatment operational conditions and the volatility of the extractives. The distribution of the extractives in the digester was also affected by the operational conditions. For the softwood, the natural extractives were comparatively volatile. It was possible to perform the gas-off under a high temperature and a high pH of the system. For the hardwood, the natural extractives were not volatile. High temperature and high pH were the ideal gas-off conditions. Apart from the extractive content, the fiber morphology also affected the bleachability of kraft pulps. For the softwood, the earlywood was easier to cook than the latewood. With the same kappa number, the final brightness of the earlywood pulp was at least 2% ISO higher than the latewood pulp because of the thinner fiber wall and faster leaching rate.

Thesis (MScFor (Forest and Wood Science))--University of Stellenbosch, 2006.
Producing high quality end products, rather than focusing on volume production, is slowly but surely becoming the main driving force in the wood processing industry of South Africa. Drying defects such as surface checks and discolouration by yellow stain and kiln brown stain are major factors in softwood timber downgrades when selecting furniture grade timber. Previous efforts to control these defects have focused on schedule adaptation, but as the industry is still mainly concerned with volume production, and because of the varying lumber price, longer schedules to control these drying defects have not yet been that attractive for the larger sawmills. In ongoing research in this laboratory, a dip treatment of freshly sawn softwood boards in an aqueous solution containing a surfactant called sodium lauryl sulphate (SLS) was used to try to influence the mechanism involved in the development of these stains. Further, complementary research is reported in this study. Firstly, the possibility of using SLS solutions to control surface mould development and bluestain was investigated. Results showed that SLS did control the development of blue stain and mould growth in open-stacked boards for up to three weeks, using concentrations as low as 0.1%, and up to two weeks in closed-stacked timber when using concentrations of 0.2%. Secondly, it was investigated whether SLS treatment would have a detrimental effect on downstream product quality; in particular, kiln dried boards and glued components for furniture manufacturing. Since SLS influenced fluid water flow during kiln drying, the treatment could have exacerbated the occurrence of surface checking due to altered moisture distribution profiles. Results of this investigation showed that the SLS treatment did not result in increased surface checking. Thirdly, as furniture quality timber treated with SLS would be glued, (and also finished with surface coatings), it was further considered important to determine if SLS treatment influenced adhesion properties of wood surfaces. Based on shear test results, it was established that SLS did not influence the adhesion properties of wood when glued with two most commonly used glues in the furniture industry i.e. polyvinyl acetate (PVAc) and urea formaldehyde (UF).

Thesis (PhD (For))--Stellenbosch University, 2012.
ENGLISH ABSTRACT: A primary reason for the existence of the forest industry is to provide a renewable and natural resource for much needed timber and fibre products. Substantial improvements in management practices are required to increase forest volume and pulp yields for increased demand. Eucalyptus grandis clonal trees of age 6.75 years, grown in a Nelder 1a spacing experiment, were sampled and analysed to describe the effect of planting density on i) growth and yield, ii) wood properties and iii) pulp and paper quality. The main objective was to populate a fibre productivity index (FPI) which would be suitable from technical and economical perspectives. A material study was conducted on the wood and in addition, two methods were developed to further describe the variability of the forest resource to i) separate growth rings by means of wood density peaks from gamma-ray densitometry and ii) calibrate near infrared (NIR) prediction models. The results indicated that planting density did not influence the variability of wood density but mechanisms affecting available soil water are important. NIR prediction models were developed to rapidly and reliably assess wood properties on a non-destructive basis. The validation models for wood density, total pulp yield, kappa number and insoluble lignin returned high predictive ability. When applied to predict chemical properties from an independent data set, the outcomes were accurate in comparison with measured data. Growth and yield functions were developed for tree survival, dominant height and basal area. They accurately predicted outcomes as demonstrated by the goodness of fit and their logical behaviour tested over the range of planting densities. When the most extreme stand density treatments, 6809 and 275 trees per hectare (TPH) were evaluated for wood and fibre properties, the larger trees grown at 275 TPH, produced wood of better quality for pulp processing; basic wood density at 0.520 g cm–3 (21 % higher), fibre cell wall thickness at 2.10 μm (18.6 % thicker) and fibre lumen diameter at 8.16 μm (9.9 % lower) than for 6809 TPH. Intra-specific tree variability of wood and product properties increased from diameter at breast height (DBH) to 35 % and then decreased to 65 % of tree height. The effect of planting density was carried throughout the product value chain up to the paper manufacturing phase. Paper with higher bulk mass and thickness and more porous sheets is most likely to be made from lower planting densities (801 and 275 TPH), and stronger, smoother and denser paper is most likely to be made with trees at high planting densities (6809 or 2336 TPH). From the growth and yield and materials investigation, technical indicators identified to populate a fibre productivity index were: i) mean annual increment (MAI) as a forestry growth indicator, ii) wood density, summarising the composition of wood and, iii) pulp yield, the indicator of the amount of fibre processed through a chemical cooking process. Delivered cost of timber to the mill, was identified as the most suitable economic indicator which included fixed costs elements, variable costs and aspects of mill efficiency. The product of the technical and economic indicators concluded in a profit/loss scenario of producing 1 ton of pulp was deemed the best index to describe the entire and integrated value chain. This index, termed the Fibre Productivity Index (FPI) at the Mill, denoted as FPMill, is an integrated index that is easy to interpret in the realms of a forestry - pulp manufacturing, and can be used for differential pricing of timber for wood quality.
AFRIKAANSE OPSOMMING: 'n Primêre rede vir die bestaan van die bosbouindustrie is om ‘n hernubare, natuurlike hulpbron vir hout en vesel te voorsien. Aansienlike verbeterings in bestuurspraktyke is nodig om die houtvolume en pulpopbrengste vir die toename in aanvraag te verhoog. Eucalyptus grandis klonale bome met ‘n ouderdom van 6.75 jaar en wat in 'n Nelder 1a spasiëring eksperiment gegroei is, is versamel en ontleed om die effek van opstandsdigtheid te beskryf op a) groei en opbrengs, b) houteienskappe en c) pulp- en papiergehalte. Die hoofdoel was om 'n veselproduktiwiteitsindeks (FPI), wat geskik sou wees in terme van tegniese en ekonomiese perspektiewe, te ontwikkel. 'n Materiaalkundigestudie is op hout uitgevoer. Twee metodes is ontwikkel om die variasie in hout as natuurlike hulpbron te beskryf deur a) vroeëhout- en laathoutdigtheidspieke deur gammastraal-densitometrie van mekaar te skei en variasie in groeiringe te beskryf en b) daarstelling van naby-infrarooispektroskopiese (NIR) voorspellingsmodelle. Die resultate het aangedui dat aanplantingsdigtheid nie ‘n invloed het op die variasie van houtdigtheid nie, maar dat meganismes wat beskikbare grondwater bepaal, belangrik is. NIR-voorspellingsmodelle is ontwikkel om houteienskappe op 'n nie-destruktiewe manier betroubaar te kan evalueer. Die validasiemodelle vir houtdigtheid, pulpopbrengs, kappanommer en onoplosbare lignien, openbaar akkurate voorspellingsvermoë. Wanneer dit toegepas word om chemiese eienskappe van 'n onafhanklike datastel te voorspel, was die resultate akkuraat in vergelyking met gemete data. Groei- en opbrengsfunksies is ontwikkel vir mortaliteit, dominante boomhoogte en basale area. Akkurate voorspellingsuitkomste is verkry soos gedemonstreer deur die logiese gedrag wat getoets is vir alle plantdigthede. Toe die mees ekstreme opstansdigtheidbehandelings vir hul hout- en veseleienskappe geëvalueer is, was die hout van die groter bome, teen 275 stamme per hektaar (SPH), van beter gehalte. Dit was veral prominent vir houtdigtheid van 0.520 g cm-3 (21 % hoër), veselselwanddikte van 2.10 μm (18.6 % dikker) en vesellumendeursnit van 8.16 μm (9.9 % laer) as by die hoër (6809) SPH. Intra-spesifieke boomvariasie van hout- en produkeienskappe het toegeneem van deursnee op borshoogte (DBH) tot 35 % en dan weer afgeneem tot 65 % van die boomhoogte. Die effek van plantdigtheid is regdeur die produkwaardeketting tot by die papiervervaardigingstadium sigbaar. Papier met hoër basismassa en dikte, en meer poreuse papiervelle kan meer waarskynlik van laer aanplantdigtheid (801 en 275 TPH) bome gemaak kan word. Papier wat sterker, gladder en digter is, kan waarskynlik gemaak word van hout van bome teen hoë aanplantdigthede (6809 of 2336 SPH). Die veselproduktiwiteitindeks wat ontwikkel is uit die materiaalondersoek en tegniese aanwysers wat geïdentifiseer is sluit in i) gemiddelde jaarlikse aanwas, as 'n bosbou groei-indikator, ii) houtdigtheid, wat ‘n opsomming van die samestelling van hout is, en iii) pulpopbrengs; die aanduiding van die hoeveelheid vesel verwerk deur 'n chemiese verpulpingsproses. Gelewerde koste van hout by die pulpmeul is geïdentifiseer as die mees geskikte ekonomiese aanwyser wat vaste kosteelemente, veranderlike koste en aspekte van die meul se doeltreffendheid insluit. Die produk van die tegniese en ekonomiese aanwysers is saamgevat in 'n wins / verlies opsie vir die vervaardiging van 1 ton pulp, en is beskou as die mees geskikte indeks om die geïntegreerde waardeketting te beskryf. Dié indeks, die sogenaamde Vesel Produktiwiteitsindeks (VPI) by die Pulpmeul, aangedui as VPMeul, is 'n geïntegreerde indeks wat maklik is om te interpreteer in 'n bosbou - pulpvervaardigingsopset, en kan gebruik word in die differensiële prysbepaling van hout waarby die kwaliteit in ag geneem word.

Understanding how different processing variables influence wood welded bonds is vital if the technique will ever be used to create engineered lumber without using adhesives. A variation of vibration welding, wood welding uses pressure and friction to bond materials together. During welding, heat causes a softening in the wood, a naturally occurring composite material. This softening leads to fiber entanglement and a bond forms upon cooling. The goal of this research was to investigate several processing aspects of the wood welding procedure. A prototype wood welding machine, designed and fabricated from the ground up, was used to investigate the effects of various welding parameters using birch wood. Wood welds were evaluated on the basis of bond coverage and ultimate shear strength. Four experiments were performed: welding frequency and duration interaction, grain orientation effects, alternative welding completion metrics, and strength development over time. During the wood welding process, three distinct phenomena were repeatedly observed: smoke creation, welding residue formation, and an audible pitch change. The presence of each was recorded for every wood welded specimen and used later in additional data analysis. Investigating each of the welding phenomena was done in an attempt to better characterize when fusion was achieved at the weld interface. ImageTool, an image analysis software package, was used to investigate and quantify the often irregular bonds exposed after shear fracture. The results of the various welding variables were analyzed on the basis of shear strength and bond uniformity. From the birch samples, it was shown that better bonds result from lower welding frequencies and longer welding durations. The grain orientation analysis demonstrated that welding orientation marginally affects the average shear strength of the wood weld. The data from the alternative welding metrics suggests that welding time is not a quality indicator of welding completion (bond coverage). The strength development trials confirmed previous research; wood welds obtain most of their strength in a relatively short period of time. Douglas fir and poplar both proved to be weldable for the first time, but they were sufficiently weaker than birch. When welding was attempted with Douglas fir under similar pressures used for birch, Douglas fir samples would commonly “washboard.” With reduced welding pressure, Douglas fir formed wood welds more easily.

Thesis (PhD (Forest and Wood Science))--University of Stellenbosch, 2006.
The discolouration of South African softwood during kiln drying can reduce the value of furniture grade lumber. Thermal discolouration of wood, as found due to heat treatment, produces a homogeneously browner colour in wood than is normally expected. This type of discolouration is attributed to reactions of the macromolecules present in wood and is found in both hard- and softwoods. Yellow stain and kiln brown stain can severely alter the colour of the outer few millimeters of a wooden board and is attributed to the reaction of water-soluble sugars and nitrogenous compounds, present in the wood sap, after deposition at the wood surface due to liquid or capillary water flow during drying. A discussion of the mechanism of discolouration due to yellow stain and kiln brown stain would be incomplete without a good understanding of the liquid flow of water during drying above fibre saturation point. This thesis brings the two concepts of liquid water flow and discolouration in context and is presented in four chapters: • an introduction motivating the aims of the investigation (Chapter 1); • a literature review of factors which may influence discolouration and liquid water flow during drying (Chapter 2); • original manuscripts describing the discolouration of South African softwood and liquid water flow in hard- and softwood (Chapter 3); and • a final conclusion that links up the results from the investigations (Chapter 4). The investigations into the occurrence of yellow stain and kiln brown stain showed that the intensity of these types of discolouration was influenced by geographical origin (and/or climate), tree species, planing depth of dried lumber, and kiln schedule parameters like dry- and wet bulb temperature and time. The characteristic discolouration pattern of yellow stain and kiln brown stain indicated that this stain type was related to the wetline phenomenon that is found during the liquid water flow phase of drying wet wood. Thermal discolouration, on the other hand, occurred homogeneously throughout the volume of lumber and is, therefore, not related to free water flow, but to chemical changes of the macromolecules in wood. The results of the liquid water flow investigations support the invasion percolation theory of drying that states that the largest meniscus will retract into a drying liquid-filled capillary network until it is not the largest meniscus anymore. Fluctuations in the rate of moisture loss from the cores of wood pieces above fibre saturation point were also found. The pattern of fluctuation differed appreciably between Betula verrucosa and Pinus radiata. In both cases, the start of the last phase in rate of moisture loss from the core coincided with a reduction in the cross-sectional area of the drying wood piece. This behaviour is explained by the hypothesis that distinct capillary size classes are emptied of free water, in order, from large to small. As smaller capillaries are emptied, the capillary forces become greater, to the point where the forces are great enough to cause permanent or temporary deformation of the remaining water-filled capillaries. Classification and regression tree analysis was a useful statistical technique to analyse a large multivariate dataset. The importance of kiln schedule temperatures and planing depth to control yellow stain and kiln brown stain was clearly pointed out by the technique, which can help to simplify the control of colour quality during the industrial processing of wood.

Thesis (MScFor) (Forest and Wood Science)--University of Stellenbosch, 2007.
While the contribution of non-timber forest products (NTFPs) in sustaining livelihoods of the poor is gaining global attention, the importance of woodcarving trade in sustaining the livelihoods of the poor people has been poorly researched. A study was conducted in Cape Town area of the Western Province, South Africa to assess the contribution of woodcarving trade to the livelihoods of the traders and the dynamics of the trade, and institutional constraints impacting on the development of the trade. A total of 61 traders in wood carving, as well as municipal authorities and key informants, were interviewed using structured questionnaires; note taking, personal observations, and in-depth interview based open-ended questions. The findings of the study revealed that the woodcarving trade is a highly male (69%) dominated activity. Most traders were married (55%) and most of the respondents (63%) fell within the active age group of 21-35 years. The wood carving trade was dominated by highly literate people with 66% and 25% having reached secondary and tertiary education, respectively. The study also revealed that “earning a living” represented the single most important factor (70%) that pushed people into the wood carving trade. Most traders (85%) did not own property but for those who owned property, 56% were South Africans followed by Zimbabweans (22%). The study showed that most of the woodcarving products arriving in the Western Cape come from the SADC region accounting for 78% of the products. Malawi (36%), Zimbabwe (30%) and Kenya (13%) are the main sources of the wooden crafts curio into the Western Cape woodcraft market. The study also found that Dalbergia melanoxylon from Zimbabwe (47%) and Malawi (16%) and Brachylaena huillensis from Kenya (47%) and Afzelia quanzensis from Zimbabwe (27%) represent the most traded wood species. The wood for carving was mainly accessed through intermediate agents (48%) and on site purchase (43%); and polishing represented the most important process (80%) of value adding compared to painting and shining. Personal cars (38%) and buses (36%) were the main means of transportation used compared to other forms of transport. It was shown that cost (48%) and customer based price (33%) represented the main pricing methods used by traders. Shop owners had an average income estimated at R 6, 450 and R 2, 692 in good and lean month sales, respectively. In addition, seasonality represented the single most important factor (56%) threatening the woodcarving industry and the livelihood of urban traders compared to factors such as quality of wood product (18%) and scarcity of the resource (10%). This study found that traders had difficulties accessing physical infrastructures (87%); social assets (50%) and human capital (74%). On the other hand, 62% of the traders did not seem to have problems accessing natural assets. As a livelihood strategy, traders also undertook multiple activities including sale of minor products as well as soliciting extra help from companions and/or hiring extra help during peak seasons. For the sustainability of the woodcarving trade in the Western Cape, there is a need for sustained, long-term management of wood species used for carving through domestication and use of alternative wood species. In addition, policies should promote: (i) integrated resource use that will ensure maximum utilisation of the wood from a single tree e.g. timber and wood carving, (ii) the culture of association and cooperation among traders, (iii) collaborative mechanisms involving all players from the forest and the tourism sector as well as the traders, (iv) secure traders’ livelihood assets, (v) an environment favourable to business venture’s expansion and growth through micro-finance and micro-credit schemes.

Thesis (MScFor (Forest and Wood Science))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: The objective of this study was to develop and assess a methodology of using pruning information (age and height) and ring width measurements on increment core samples taken at breast height from standing pruned Pinus patula trees for modeling the knotty core sizes in the pruned section of a tree. A total of 170 trees from 17 compartments, representing a wide variety of growth sites from the Mpumalanga escarpment, were selected and destructively sampled. Sample trees were selected to represent the productive timber volume available from the compartments using stratified sampling. Sample discs were removed at breast height (1.3m) and at six meter height. After drying and sanding, the cross-sectional surfaces of one surface of each of the discs were scanned on a document scanner and the ring widths measured, using an image analysis program. A preliminary study, using 30 discs, was undertaken to ascertain the appropriate number of radii per disc to measure. A comparison between results of two opposite radii, as opposed to four radii, showed that the difference in mean ring width resulting from the two approaches was statistically not significant. In practice this means that for ring width assessment, sampling of increment cores opposite to one another at breast height would be sufficiently accurate to study average ring width variation across the radius of a tree. A study was also conducted to determine to what accuracy ring widths at six metre height could be predicted from breast height measurements. It was shown that cumulative growth at six metre height can be predicted from cumulative growth at breast height, site index and cambial age at breast height as independent variables (R2 = 0.96). Ring width measurements at breast height can, therefore, be used to predict incremental growth throughout the pruned section. Combined with available information on the pruning history of a stand (pruning heights and pruning age), this study proved that quantitative knowledge on incremental growth can be used as a basis for estimating changes in knotty core sizes along the entire pruned section of the stem. Analysis of variation for the entire data set from ring width measurements showed that there was far greater variation in knotty core percentages (the percentage of diameter occupied by knotty core) between different compartments than within compartments. Within a tree, the knotty core percentages between three stem sections, 0-2.4m, 2.4–4.8m, and 4.8-7m, were found to increase significantly from the bottom section (49.1%) to the top section (65.4%). A single 2.4m log from the pruned section of each tree was removed and processed into sawn timber at a sawmill. After drying of the boards, a sub-sample of sawn boards from 17 logs, one log from each compartment, was selected and reconstructed into log form. From the reconstructed log (reconstructed to represent their original position in the log) the actual knotty core size was estimated by measuring the distance from the pith to the end of the branch stub. A comparison of the actual knotty core sizes and the modelled knotty core sizes of a sub-sample of trees showed only a modest relationship (R2 = 0.62). Reasons for this might be variability in pruning quality, inaccurate pruning records, nodal swellings and the methodology used to measure the actual knotty core sizes. Knowledge of knotty core sizes of standing trees can be used for many different purposes. Two applications that were assessed and found to be useful include decision support for cross cutting logs and for sawmill production planning purposes. Sawmill simulation software was used to evaluate value -and grade recoveries under different scenarios. Results showed that cross-cutting the pruned sections of logs from a compartment with large within-tree knotty core size variation into shorter logs, as opposed to keeping the pruned sections as single logs, result in increases in grade and value recovery. It was also shown that sawing of pruned logs from compartments with relatively small knotty cores, results in much better grade recoveries than logs from compartments with relatively large knotty cores (this information will be useful for production planning purposes). It can be concluded that the methodology proposed to reconstruct knotty cores from tree ring measurements has the potential to be used as a decision aid in the forest and forest products industry.

Thesis (MScFor (Forest and Wood Science))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: Mid rotation fertiliser application is generally practised in forestry to enhance nutrient availability in areas were soils are impoverished and do not provide sufficient nutrients for high productivity. Generally speaking there is great potential for mid rotation fertiliser in pine plantations, but stand and site characteristics such as water availability, soil depth, stand density and available nutrients need to be considered before fertiliser treatments are implemented. Foliar nutrient analyses were used to estimate nutrient availability. These levels were measured throughout the study and were used to implement specific fertiliser treatments that would boost nutrient availability. Treatments consisted of an unfertilised control, a single fertiliser application (1F) and two fertiliser applications over two consecutive years (2F). Leaf area index (LAI) and stem volume increment were measured in order to evaluate its influence on growth efficiency. LAI was estimated using the gap fraction method with the use of a ceptometer. Volume increment was calculated with diameter and height measurements. Basal area was calculated by means of diameter measurements. These growth responses were used to determine the effect of increased nutrient availability and although increases were found in LAI, volume increment, basal area increment and growth efficiency, none were significant. The lack of significance may be due to relatively large variations in other factors such as stand density and initial volume of the experimental plots. The 18 month monitoring period apparently did not allow complete reaction time to increased nutrient availability and limited our understanding of the responses somewhat. Despite this, the magnitude of some growth responses was large as nutrient ratios in the foliage increased to levels within the norms range. Increases in current annual volume increment (CAI) of 3.48 m3 ha-1 a-1 and 3.62 m3 ha-1 a-1 in 1F plots at Grabouw and La Motte plantations indicated that it may be economically feasible to fertilise at mid rotation age as the NPV and IRR increased over a projected 25 year rotation. The Grabouw site had the most significant response with regards to CAI in 2F treatment with a mean volume increment of 5.43 m3 ha-1 a-1. The mechanism of the response was examined further by taking water availability and soil characteristics into account. The seasonal climatic effect (length of the moisture growing season) had a significant influence on the response to fertilisation.
AFRIKAANSE OPSOMMING: Die toediening van mid-rotasie bemesting word algemeen in bosbou toegepas om voedingstofbeskikbaarheid te verhoog in areas waar voedingstowwe onvoldoende is vir hoë produktiwiteit. Daar is oor die algemeen ruim potensiaal vir mid-rotasie bemesting in denne plantasies, maar eienskappe soos waterbeskikbaarheid, gronddiepte, opstanddigtheid en beskikbaarheid van voedingstowwe moet in ag geneem word voor optimum bemestingtoedienings bepaal kan word. Blaaranalise is gebruik om voedingstofbeskikbaarheid in plantasies te skat. Hierdie voedingstofvlakke is deurgans gemeet en is gebruik om spesifieke bemestingsbehandelings te implementeer wat voedingstofbeskikbaarheid kon opstoot. Behandelings het bestaan uit ‘n onbemeste kontrole, ‘n eenmalige kunsmistoediening (1F) en twee kunsmistoedienings in opeenvolgende jare (2F). Blaar oppervlak indeks en toename in stamvolume is gemeet om die invloed daarvan op die effektiwiteit van groei te bepaal. Blaaroppervlakindeks is bepaal deur middel van die gapingfraksie metode met behulp van ‘n stralingsmeter. Toename in volume is bereken met stamdeursnee en hoogte meetings. Basale oppervlakte is bereken deur middel van deursnee metings. Hierdie groeireaksies is gebruik om die effek van verbeterde voedingstofbeskikbaarheid te bepaal. Al die groeireaksies het toegeneem maar was nie statisties beduidend nie. Die gebrek aan beduidende toename kan toegeskryf word aan variasies in opstandsdigtheid en oorspronklike volume van die bome in die navorsingspersele. Die toetstydperk van 18 maande het moontlik nie genoeg tyd gegee vir die bome om op die toename in voedingstofbeskikbaarheid te reageer nie. ‘n Goeie groeirespons is wel waargeneem waar die voedingstofverhoudings in die naalde aanvaarbare norme bereik het. Die toename in volume aanwas van tussen 3.48m3 ha-1 a-1 en 3.62 m3 ha-1 a-1 in 1F persele by Grabouw en La Motte plantasies het aangedui dat dit ekonomies lewensvatbaar is om op mid-rotasie ouderdom bemesting toe te dien aangesien die netto teenswoordige waarde en die interne opbrengs koers toegeneem het op ‘n geprojekteerde 25 jaar rotasie. Die persele op Grabouw plantasie het die mees beduidende respons getoon met betrekking tot huidige jaarlikse aanwas (5.43 m3 ha-1 a-1 in die 2F perseel). Die meganisme van die respons is verder nagevors met inagneming van waterbeskikbaarheid en grondeienskappe. Die seisoenale klimaatseffek (lengte van die vog-groeiseisoen) het ‘n beduidende impak op die respons tot bemesting.

The primary objective of this study was to investigate mould growth resistance of different types of wood products which include the sheathing and framing within full scale wall assemblies. Secondary objectives were to investigate the difference in mould growth resistance between borate-treated and untreated wood products as well as provide information about mould growth under different temperature and humidity conditions for treated and untreated wood products.

The objective of the study is to better understand mould growth, and to examine the effects of varying high moisture conditions on wooden products and the mould growth which may result. More importantly this will be examined on full scale wall assemblies; to date mould growth studies have only been performed within a laboratory on small samples of materials. Moreover, this study recreates the conditions which evidently cause mould growth on full scale wall assemblies. Tests were performed within a climate chamber on three full scale wall assemblies. The original scope of this study included an examination of the sheathing and framing components within a full scale wall assembly, however this study will focus mainly on the sheathing.

Results of this study indicate that the relative humidity conditions needed for mould growth on wood are higher than originally believed (i. e. , significantly greater than 80%RH). During the first eight weeks of test number one the relative humidity at the surface of the sheathing was held constant at 95% and little mould growth was observed on the untreated sheathing (mould growth index of 3 or less); little or no mould growth on the treated sheathing (mould growth index of 1 or less). The second and third tests demonstrated that the presence of liquid water greatly accelerated the time to germinations, the amount of mould growth (up to a mould growth index of 6), and the rate of mould growth. All three tests clearly showed that borate-treatment reduced the amount of mould growth; however, the concentration of borate-treatment, and the types of materials treated, does affect the resistance of mould growth. Furthermore, there was some evidence to suggest Borate treatments of the plywood increased the time to germination significantly, from a few weeks to 16 weeks in this study, but once mould growth was initiated, the rate of mould growth was similar to that of the untreated plywood. Two mathematical models to determine mould growth were examined: Viitanen and WUFIBIO (Sedlbauer). Viitanen?s model predicted time to germination and rate of growth rate well for untreated plywood, and WUFIBIO predicted time to germination but not the growth rate. It was also found both models err on the side of caution in predicting mould growth.

Recommendations include improvements to the test method and producers, and for future work.

Thesis (PhD)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: Polymer composites, and in particular wood-polymer composites have become commercially and environmentally important materials. Studies in polyolefin-wood composites have mostly focused on polypropylene (PP) and polyethylene (PE). To our knowledge, no study has been undertaken on advancing impact polypropylene copolymer (IPPC)-wood composites as a suitable alternative to using PP and PE. IPPC have proven to be a suitable alternative to PP at low temperatures to improve impact resistance for manufactured polymer products, and could be a great addition to improved properties for wood polymer composites. This study shows that the physical properties of IPPC-wood composites can be markedly improved when compatibilizer(s) are used to improve the distribution of the wood within the matrix, as well as improving the interaction between the wood and the polymer matrix.. The use of different compatibilizers, vi polypropylene-graft-maleic anhydride (PPgMA) and poly(ethylene-co-vinyl alcohol) (EvOH) results in different physical properties. Using simple admixtures of the PPgMA and EvOH in IPPC-wood composites result in a large spread of results, while pre-reacting the PPgMA and EvOH to form a joint compatibilizer gives reproducible results w.r.t the physical testing. A study of the fundamental interactions of the compatibilizer(s) with the molecular components of the IPPCs was undertaken. The IPPCs used were fractionated by preparative temperature rising elution fractionation, and the fractions were mixed with the compatibilizers. To this end, fluorescence microscopy was utilized to study the interaction. The results clearly indicate that the interaction of the PPgMA with the fractions differ from that of the EvOH. These differences can be explained in terms of the chemical composition distribution within the IPPC fractions. Atomic force microscopy (AFM) was used to study adhesive forces between compatibilizer, polymer and cellulose and lignin. Successful coating of AFM tips with PPgMA and EvOH was achieved. Whilst interactions based on chemical force microscopy (CFM) could not be quantified, the AFM results in conjunction with fluorescence spectroscopy provided meaningful insight in the way that compatibilizers interact with both the wood and the impact copolymers used in this study.
AFRIKAANSE OPSOMMING: Polimeer saamgestelde material, en meer spesifiek hout-polimeer saamgestelde material het die afgelope tyd belangrike produkte geword, beide kommersieel en in verband met omgewingvriendelikheid. Navorsing op die gebied van poli(olefien)-hout komposiete het tot op hede meestal gefokus op die grbruik van poli(propileen) (PP) en poli(etileen) (PE). Sover dit on kennis strek is daar nog geen studie gedoen om die gebied van impak polipropileen kopolimere (IPPK)-hout komposiete uit te bou nie. IPPKs is ‘n geskikte alternatief vir PP in veral laetemperatuur aanwendings. Die gebruik van IPPKs as matriks vir die hout komposiete kan ‘n groot staqp vorentoe beteken. Hierdie studie wys dat die fisiese eienskappe van iPPK-hout komposiete merkwaardig verbeter kan word waneer versoeningmateriale gebruik word om die verspreiding van die hout in die polimeermatriks sowel as die interaksie tussen die hout en polimeer te verbeter. Die gebruik van verskillende versoenings material, t.w poli(propileen-ent-maleinsuur anhidried) (PPeMA) en pol(etlieen-ko-viniel alkohol) (EVOH). Deur gebruik te maak van eenvoudige mengsels van PPeMA en EVOH in IPPK-hout composite het ‘n geweldige wye verpreiding van resultate tot gevolg gehad, terwyl ‘n voorafgaande reaksie tussen die PPeMA en die EVOH om ‘n saamgestelde versoeningmateriaal te maak tot gevolg gehad het dat reproduseerbare resultate verkry kon word. ‘n Studie van die fundamentele interaksies van die versoeningsmateriale met die molkulêre komponente van die IPPKs is uitgevoer. Die IPPKs is gefraksioneer deur preparatiewe temperatuur-stygende uitloog frakasionering en die fraksies is gemeng met die versoeningmateriale. Fluoressensie mikroskopie is gebruik om hierdie interaksies te bestudeer. Die resultate dui duidelik daarop dat die interaksie van die PPeMA met die fraksies verskil met die van die EVOH. Die verskille kan verduidelik word aan die hand van die chemiese samestelling verspreiding van die IPPK fraksies. Atoomkrag mikroskopie (AKM) is gebruik om die adhesive-kragte tussen die versoeningmateriale, polimere, sellulose en lignien. AKM tippe is suksesvol bedek met PPeMA en EVOH, onderskeidelik. Alhoewel interaksies gebaseer op chemiese krag mikroskopie (CKM) nie gekwantifiseer kon word nie, lewer hierdie resultate tesame met die fluoressensie spektroskopie unieke insig in die manier wat versoeningmateriale met beide die hout en die polimeer reageer.

In response to the furniture industry’s growing demand for raw material, large volumes of juvenile silver birch and downy birch stems available from pre-commercial thinning operations in Sweden’s forests could offer solutions. However, such stems are not currently used on an industrial scale, and most research conducted on birch stems in general has neither focussed on young trees nor the potential use of the central stem part around the tree pith. The resulting lack of knowledge about the juvenile part of birch wood thus requires additional information about the material properties of birch, which could encourage its use for various purposes in the furniture and other industries. The initial literature review performed for this thesis has highlighted some properties of juvenile birch required for its use as a furniture material, as well as identified topics concerning the physical characteristics of juvenile birch about which knowledge is currently limited. Consequently, the objectives of this thesis were to explore some characteristics of juvenile birch—bark thickness, wood-to-bark bonding ratio after drying, variations in the density and width of growth rings, and anatomical growth response to fertilisation—in order to increase the knowledge. The material studied came from mixed birch and Norway spruce stands at two sites in southern Sweden, namely Asa and Toftaholm. The birch stems were naturally regenerated silver birch and downy birch, with breast height diameters between 30 and 83 mm. Fertilised and unfertilised silver birch trees were sampled at Toftaholm, whereas unfertilised stems of silver birch and downy birch were sampled at Asa. The characteristics of stems from the pith to bark (radial direction) and along the stem (longitudinal direction) were measured. The wood-to-bark bonding ratio on downy birch after drying was calculated as the percentage of the stem circumference with full contact between the wood and bark, while oven-dry density and basic wood density for silver birch were determined by using the water displacement method. The impact of ring width on wood density was statistically analysed, and an image analysis of the wood anatomy was conducted to elucidate their relationship. Amongst the results, bark thickness along the stem had the highest deviation in the section closest to the stump. Moreover, the wood-to-bark bonding ratio after drying measured for juvenile downy birch seemed to depend more on the stem’s diameter than the sampling height along the stem. Such results are relevant for processors seeking to estimate the volume of wood under the bark. The wood-to-bark bonding ratio was highest for diameters between 30 and 39 mm, and neither did that relationship correlate with the sampling height along the stem. Variation in wood density in the radial and longitudinal directions in juvenile silver birch suggested that such density negatively correlated with growth rate (ring width). That relationship held true for stems at each site and between the sites, irrespective of management or growing conditions. As expected, mean wood density was lower in fertilised trees than in unfertilised ones, and towards the bark, radial density increased more in trees that grew more slowly. At the same time, variation in longitudinal density in young silver birch trees was low. Quantitative wood anatomy studies confirmed that the fertilised juvenile birch had younger cambia, thinner cell walls, and fewer vessels per mm2 than unfertilised trees in the same diameter class. Overall, the knowledge generated in the study may facilitate the industrial use of juvenile birch stems and wood in interior and furniture applications. The role of wood anatomy in determining the mechanical performance of juvenile birch stems should be further examined, however, to possibly reveal new opportunities for the use of juvenile birch.
Det finns ett växande behov av råvaror till möbelindustrin. Stammar av juvenil vårtbjörk och glasbjörk finns tillgängliga i stora volymer från röjning i svenska skogar. För närvarande finns det inget storskaligt industriellt nyttjande av det virket. Bättre kunskap om dess virkesegenskaper kan öppna upp möjligheterna till olika användningsområden. Dock har en majoritet av den befintliga björkforskningen ofta exkluderat studier av innersta veden närmast kärnan, vilket resulterat i en låg kunskapsnivå om det juvenila virket. I den inledande litteraturstudien i denna uppsats belyses vilka krav som ställs på materialegenskaperna i möbelvirke. Vidare identifieras befintliga kunskapsluckor i fysiska och mekaniska egenskaper för juvenil björk. Målet med denna uppsats är därför att utforska några egenskaper, såsom barktjocklek, barkvidhäftning efter torkning, densitet och årsringsbreddsvariation samt hur gödsling kan påverka vedanatomin. Materialet kom från blandskogsbestånd med gran och björk i Asa och Toftaholm i Götaland. Björkarna var självföryngrad vårtbjörk och glasbjörk och stammarna hade en brösthöjdsdiameter mellan 30 och 83 mm. I Toftaholm var en del av beståndet gödslad respektive ogödslad vårtbjörk. Från Asa togs stammar av både vårtbjörk och glasbjörk. Virkesegenskaper och dess variationer i stammens radiella och longitudinella riktning studerades. Vidhäftningen av barken till veden efter torkning bedömdes procentuellt på omkretsen av ändträet. Relativ torrdensitet och rådensitet mättes. Påverkan av årsringsbredd på veddensitet analyserades statistiskt och vedanatomin studerades med mikroskop och bildanalys för en vidare förståelse av dess samband med gödsling. Resultaten gällande barktjocklekens variation visade att den nedre delen av stammen hade störst medelavvikelse. Dessa resultat kan vara relevant information för vidareförädling efter avbarkning. Barkens vidhäftning till veden efter torkning mättes på juvenil glasbjörk. Det visade ett visst samband med stamdiameter där den högsta vidhäftningen fanns på stammarna med en diameter mellan 30 och 39 mm. Sambandet var däremot inte korrelerat till stamhöjden där provet togs. Densitetsvariation i radiell och longitudinell riktning studerades för juvenil vårtbjörk. Densiteten hade en svag negativt korrelation till årsringsbredd. Detta samband sågs både inom bestånd och mellan bestånd med olika tillväxtförhållande samt skötsel. Medeldensiteten för virket var, som förväntat, lägre i de gödslade träden jämfört med de ogödslade. I den radiella riktningen  hade det senvuxna virket en högre faktor på densitetsökningen. Den longitudinella densitetsvariationen i unga vårtbjörkar var låg. Kvantitativa vedanatomistudier bekräftade att ungdomsveden i gödslad vårtbjörk hade en lägre kambiumålder, tunnare cellväggstjocklek och färre kärl jämfört med ogödslade träd med samma diameter, resultat som tidigare påvisats för mogen björk. Sammanfattningsvis kan resultaten från den här uppsatsen förbättra kunskapen och därmed underlätta för en industriell användning av juvenila björkstammar inom inredning och möbler. Dock bör vedanatomins påverkan på de mekaniska egenskaperna för juvenila björkstammar studeras vidare. Det kan möjliggöra nya användningsområden för juvenil björk.

Thesis: M.B.A., Massachusetts Institute of Technology, Sloan School of Management, in conjunction with the Leaders for Global Operations Program at MIT, 2017.
Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, in conjunction with the Leaders for Global Operations Program at MIT, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (page 60).
Pacific Gas & Electric Companys (PG&E) electric distribution system includes approximately 2.4 million wood utility poles. The Pole Test & Treat (PTT) program at PG&E is responsible for inspecting these poles, prolonging their service life through the use of chemical treatments or structural reinforcements, and identifying poles that need to be replaced. Following industry best practices and taking advantage of the vast knowledge and experience of the PTT team, PG&E inspects poles every 10 years. The company believes that the next step in improving the performance of the PTT program is to leverage the data collected since the inception of the program and utilize modern statistical methods to better understand and predict decay in their wood pole assets. In this thesis, we describe the possibilities and limitations of using PG&E's current data to predict the results of future inspections. We study both the possibility of making predictions at the individual pole level, predicting whether a pole will be rejected during the next inspection cycle, and at the aggregate level, predicting what the overall rejection rate in a subpopulation of poles will be in the future. In order to accomplish this, we first studied the available data sources and performed exploratory analysis to understand the characteristics of the different variables and form hypotheses about the main drivers of rejections during pole inspections. Next, we attempted to build a classification model to predict the results of future inspections. This showed us that our current data cannot be used to yield an accurate prediction at the individual pole level. Then, we developed a model to estimate the overall rejection rates of subpopulations of poles. The result was a prediction with a Mean Absolute Percentage Error of about 30%. While not ideal, this model gives PG&E the ability to budget and plan for future work better. Finally, we leveraged the results of the prediction model to simulate the evolution of rejection rates in the future. The simulation highlighted a well-known problem in the utility industry - the problem of aging infrastructure. The relatively low average age of poles and the low replacement rates observed in the past few inspection cycles mean that PG&E will likely experience a drastic increase in rejection rates as the average age of its pole population grows. Planning for the accompanying increase in manpower and work hours required will be of great importance to PG&E in the next few decades.
by Boyan Lyubomirov Kelchev.
M.B.A.
S.M.

Thesis (MScFor (Forest and Wood Science))--Stellenbosch University, 2008.
The characterization of soils in Nzara District of Southern Sudan in comparison to other tropical teak growing countries (Tectona grandis) – in respect of extensions to existing and/or the establishment of new teak plantations – were done by firstly considering the soils of three existing plantations: Yoboa, Mabarizinga and Nagondi, and secondly by considering soils outside and inside the existing teak plantations in respect of land uses. From these soil characterizations, it emerged that considerable positive returns can be expected from teak plantings in the area as an investment, provided that appropriate site management is implemented. Climatic data of the Nzara area compared favorably with the climatic range of areas where teak grows naturally and the world’s dominant producers: mean annual rainfall 1350-1600 mm with a distribution over 6-8 months compares well with that of Myanmar (1250-3750 mm) and Indonesia (1511-2108 mm) both with at least 3 months of dry season. The mean annual temperature of 28-350C compares well with 15-410C and 30-320C of Myanmar and Indonesia respectively. The Yoboa and Mabarizinga sites should be prioritized as they appear slightly more suitable than the Nagondi site. All three sites have a dominant soil texture of Sandy Clay Loam similar to Sandy Loam of most areas of other tropical countries where teak is growing well (such as India, Indonesia and Nigeria). Yoboa and Mabarizinga however distinguish themselves by having the highest soil pHwater values range from 6.4±0.56 and 6.04±0.7 in top soils; 5.91±0.5 and 5.46±0.61 in subsoils at Yoboa and Mabarizinga respectively; the highest soil organic matter content 1.8±0.34% and 1.92±0.43% in topsoil 0.89±0.16% and 1.13±0.19% in subsoils; as well as the highest P content in both available (0.09±0.04% and 0.03±0.04% for topsoils) and total forms (1.19±0.26% and 0.9±0.3% also on topsoils). These values though very low in absolute terms, are not much different from those of other tropical teak-growing countries. Management strategies intended to preserve and improve the present status, particularly the protection of top soil horizons against mainly water erosion, would be able to boost the site productivity.

Thesis (MFor ) -- University of Stellenbosch, 2003.
ENGLISH ABSTRACT: The bulk of paper grades destined for the printing industry are produced on modern paper machines which continuously become wider and faster. In order to improve printability, print quality and dimensional stability, such papers contain a large percentage of mineral pigments either in the form of internal loading or external coatings. Although mineral pigments exercise a substantial beneficial effect on paper surface quality, unfortunately these minerals do not contribute towards sheet strength and machine runnability. Today's papermakers are faced with the dilemma of producing highly filled and coated printing papers with low grammages on faster running paper machines, but often lacking the required quality of fibre resources to secure a smooth runnability of such at high speeds. Standard fibre furnishes will have to be upgraded with special types of reinforcing fibres in order to meet the demands of sheet strength and machine runnability. The investigation had succeeded to identify a new suitable fibre resource, which would satisfy the demand of a reinforcing type natural material.
AFRIKAANSE OPSOMMING: Die oorgrootte meerderheid tipes papier wat vir die drukkersbedryf bestem is, word op moderne papiermasjiene vervaardig wat steeds breër en vinniger word. Om die drukbaarheid, drukkwaliteit en dimensionele stabiliteit te verbeter, bevat sulke papiere groot hoeveelhede minerale pigmente wat in die vorm van interne ladings of as eksterne bestrykings teenwoordig is. Alhoewel minerale pigmente -n merkbare voordelige effek op die papier oppervlakte-kwaliteit uittoefen, dra sulke pigmente ongelukkig nie by tot die sterkte en loopvermoë van die papier nie. Die hedendaagse papiervervaardiger word konfronteer met die dilemma om swaar gevuldeen bestrykte drukpapiere met lae oppervlaktegewig op vinniger lopende papiermasjiene te vervaardig. Dit gebeur dikwels sonder die beskikbaarheid van die nodige hoëkwaliteit veselbronne om te verseker dat die loopvermoë van die papier teen hoë spoed nie benadeel word nie. Standaard veselsamestellings salopgegradeer moet word met spesiale tipe versterkingsvesels om aan die uitdaging van hoë velsterkte en masjien-Ioopvermoë te voldoen. Hierdie ondersoek het daarin geslaag om 'n nuwe geskikte veselbron te dentifiseer en wat aandie behoeftes van 'n versterkingsvesel sal voldoen.

Thesis (MScFor (Forest and Wood Science))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: Balau, a group consisting of 21 Shorea species, is widely used for outdoor application. In South Africa, Balau is one of the most popular materials used for decking. Due to the increasing scarcity of Balau, it is of economic importance to investigate the possibility of a substitute timber for decking material. One possible timber could be Colorado, a mixture containing one or more of the following: Eucalyptus camaldulensis, Eucalyptus tereticornis and their hybrids. These two species and their hybrids are extensively cultivated in countries such as Australia, India and parts of South America because of their short rotation period and easy adaptability to a wide variety of soil and climatic factors. The timber was initially utilized as raw material for the pulp and paper industry but is now gaining importance in structural uses like furniture, flooring and decking. The aim of this exploratory study was to investigate relevant material properties and to examine the natural and accelerated weathering behaviour of Colorado and Balau to predict Colorado’s suitability as decking material. It was found that Colorado had smaller vessel lumina, fewer vessels/m2 and smaller rays than Balau and had a higher density than Balau. Although both timbers had a relatively low FSP, Colorado’s FSP was 2.3 percentage points higher than Balau’s. The swelling coefficients (radial and tangential) of Colorado were slightly higher than Balau’s but Colorado’s lower swelling anisotropy can result in a lower tendency to twist in service. Colorado had a higher water soluble extractive content than Balau, which can lead to the rapid initial colour changes when the timber is exposed uncoated. The weathering performance of Colorado and Balau was investigated by exposing samples in a QUV accelerated weathering apparatus and to natural weathering at an inland and a marine location. During weathering Colorado showed a slightly higher colour change ( E*) than Balau. Balau showed a higher increase in roughness (Rz), surface checking and check formation than Colorado. Colorado showed slightly more cup than Balau, however, Balau showed much larger amounts of twisting than Colorado. No statistically significant differences were found between the hydrophobicity of the two timbers. A coating was effective in increasing the initial hydrophobicity of samples and could maintain a relatively hydrophobic surface during weathering. No statistically significant differences were found in the effect of sample cut on timber species surface wettability. Although only long term exposure studies and using substantially more samples can confirm its weathering performance, the results of this exploratory weathering study indicated that Colorado can successfully be used as a substitute decking material for Balau.
AFRIKAANSE OPSOMMING: Balau, ‘n houtsoort wat ongeveer 21 Shorea-spesies verteenwoordig, word wyd in buitenshuise aanwendings benut. In Suid-Afrika is Balau een van die mees gewilde materiale wat vir dek-doeleindes gebruik word. As gevolg van die toenemende skaarsheid van Balau, is dit van ekonomiese belang om die gebruik van ‘n moontlik plaasvervangende houtsoort vir dek-materiaal te ondersoek. Colorado, ‘n mengsel van een of meer van die volgende: Eucalyptus camaldulensis, Eucalyptus tereticornis en hibriede daarvan, kan as ‘n moontlike plaasvervanger gebruik word. Hierdie twee spesies en hulle hibriede word op groot skaal in lande soos Australië, Indië en dele van Suid-Amerika gekweek vanweë hul kort rotasieperiode en goeie aanpasbaarheid by ‘n wye verskeidenheid grond- en klimaatsfaktore. Die spesies is aanvanklik as grondstof in die pulp- en papierbedryf gebruik maar word tans al hoe belangriker in strukturele aanwendings soos byv. meubels, vloer- en dek-materiaal. Die doel van hierdie verkennende studie was om relevante materiaaleienskappe te ondersoek en om die versnelde en natuurlike verweringsgedrag van Colorado en Balau vas te stel om sodoende ‘n aanduiding van die geskiktheid van Colorado as dek-materiaal te kan kry. Daar is gevind dat Colorado kleiner vat-lumina, minder vate/m2 en kleiner strale as Balau besit en dat Colorado ‘n hoër digtheid het as Balau. Alhoewel beide houtsoorte relatiewe lae veselversadigingspunte (VVP) besit, is Colorado se VVP 2.3% persentasiepunte hoër as dié van Balau. Die swellingskoëffisiente (radiaal en tangensiaal) van Colorado is effens hoër as dié van Balau, maar Colorado se laer swellingsanisotropie kan op ‘n kleiner neiging tot skeeftrek dui. Colorado het ‘n hoër wateroplosbare ekstrakstofinhoud as Balau bevat, wat tot aanvanklik vinnige kleurveranderings kan lei wanneer die hout sonder oppervlaktemiddel blootgestel word. Die verweringsgedrag van Colorado en Balau is ondersoek deur monsters aan versnelde en natuurlike verwering bloot te stel. Eersgenoemde is in ‘n QUV versnelde verweringsapparaat uitgevoer en laasgenoemde in ‘n binnelandse en ‘n mariene lokaliteit. Tydens verwering het Colorado ‘n effens hoër kleurverandering ( E*) as Balau getoon. Balau het ‘n hoër toename in rofheid (Rz), oppervlaktekrake en kraakvorming as Colorado getoon. Colorado het effens meer kromgetrek terwyl Balau meer skeefgetrek het as Colorado. Geen statisties beduidende verskille kon tussen die waterwerende eienskappe van die twee houtsoorte vasgestel word nie. ‘n Oppervlakbedekking was effektief om die aanvanklike toename in waterwerende vermoë te verhoog en gedurende verwering te kon behou. Geen statisties beduidende verskille kon tussen die invloed van snit van die monster op die oppervlaktebenatbaarheid van die houtsoorte vasgestel word nie. Alhoewel slegs langtermyn blootstellingstudies en die gebruik van beduidend veel meer monsters die verweringsgedrag kan bevestig, dui die resultate van hierdie verkennende ondersoek aan dat Colorado suksesvol as ‘n plaasvervangende dekmateriaal vir Balau gebruik kan word.

Sitka spruce (Picea sitchensis (Bong.) Carr.) has been the most common forestry species in UK plantations for many decades. It is generally fast grown in short rotation, which has implications for quality. The harvested timber has a number of end-use applications. Of these, sawn construction grade timber is at the high end of market value. Currently, under one third of home grown sawn timber processed by sawmills achieves the required C16 or higher grading for construction class timber. Presently there is significant standing stock of 40 years old or under. Improvements in timber quality would create significant benefits for growers and processors. Distortion in kiln dried sawn timber is a considerable barrier to improving grading classification and marketability. Twist in particular accounts for around six percent of the rejections after kiln drying. Additional twist when timber dries further; in storage, at construction sites or in-service, is perceived as a marketing issue. The focus of this work was to better understand the evolution of twist during the drying process and seek to improve quality by examining the key properties in sawn timber that contribute to the formation of twist. Samples of regularly processed full size (3 m in length) sawn timber were kiln dried with no restraint to promote maximum twist. This was done in three stages to assess the impact of intermittent drying. Measurements of twist, moisture content, acoustic velocity and basic dimensions were taken before and after each drying cycle. The results showed highly significant differences between battens containing the pith and those that did not. Drying in stages did not seem to affect the linearity of the moisture content against twist relationship. Twist was seen to develop at a consistent rate throughout the process regardless of the final amount of twist accrued or the position from which the batten was sawn. Where timber is likely to dry to lower moisture content after sale it is therefore possible to predict the additional twist from the moisture content expected and allow for it by stricter grading than the twist standard demands. Twist was seen to decrease slightly during a lengthy period of storage in controlled conditions between drying cycles. This may allude to a relaxation effect which could have implications for timber distortion in-service but this would require a more extensive study before any such conclusions could be drawn. A second batch of unrelated samples, were kiln dried to 12% MC under restraint. All of these samples contained the pith along their length and all developed significant amounts of twist. This suggests that battens containing the pith will twist regardless of restraint. A method was developed to measure longitudinal shrinkage. This required the batten size to be reduced to fit the method and battens were sawn into 3 x 1 m sections. Battens were re-saturated and measured daily throughout air drying until an equilibrium moisture content was achieved. Measurements of transverse shrinkage were also taken concurrently. No relationship could be found between the longitudinal and transverse results. When plotted against the data for twist a positive relationship was found with longitudinal shrinkage. Acoustic tools were used to calculate dynamic stiffness. As the values for acoustic velocity squared correlated well with dynamic stiffness, other possible relationships were explored. Good agreement was found with twist and longitudinal shrinkage. This suggests it may be possible to predict twist in sawn timber directly or as a function of microfibril angle, using acoustic tools. A simple method for measuring grain angle was devised. Discs taken from the trees used in the drying experiment were measured for grain angle to compare with other measured properties. The measurement method worked well but the sample size was small and the discs too thin to provide good quality data quality. The results were not as instructive as expected. A vague relationship with twist was found. A repeat of the experiment with an improved method could yield more conclusive results. A method was developed to measure radial and tangential shrinkage in discs. Discs of Sitka spruce from a different source were used. Discs were saturated and allowed to dry with the expectation of cracks developing. The intention was to explore the nature of internal stresses present in intact discs and why tangential and radial shrinkage differs. As only one disc cracked the scope of comparison was limited but it was apparent that the greater shrinkage tendency in the tangential direction was responsible for radial cracking.

Graphene nanoplatelets (GNPs) were used to reinforce wood polymer composites (WPCs) in order to achieve multifunctionality. Multifunctionality could be achieved through the GNPs because of their excellent mechanical and electrical properties. The research consists of two parts: HDPE/GNP/WF composites and LLDPE/GNP composites. The HDPE part is a continuation of previous work. Here further mechanical characterisation was done (impact testing), impurities in the composites were identified, the manufacturing process that results in damaged wood particles was investigated and the Young's modulus of the composites were modeled. The impact strength was improved due to the addition of GNPs. WF composites exhibited more brittle behaviour and therefore a lower impact strength. The impurities were identified as some form of nanoclay introduced during the extrusion process. The particles were damaged during the extrusion processes. Little can be done about this as different shear configurations and/or screw speeds will result in a poor GNP dispersion and distribution. Modeling of the Young's modulus was the most accurate through applying the laminate analogy and rule of thumbs. The rule of mixtures does not represent the composites which have a preferred orientation. During the previous work done, it was found that the HDPE composite were not electrically conductive and therefore not multifunctional. The work was therefore continued with LLDPE and GNPs. LLDPE has more branches and is less dense, resulting in potential opportunities for the GNPs to form a network through the polymer. This could lead to a better conductivity. Mechanical and electrical characterisation was done of the LLDPE/GNP composites. Here multifunctionality could also not be achieved as the composites were highly electrically resistant. Mechanical testing indicated that the GNPs significantly enhance the LLDPE matrix. Here an increase of up to 170% could be seen in tensile modulus and an increase of 46% in tensile strength. Furthermore the GNPs improved the flexural properties and increase the resistance to viscoplastic deformation during residual strain testing. Overall the GNPs improve the mechanical properties significantly, but at 10wt.% GNP contents, multifunctionality could still not be achieved.

The design and implementation of a computer-assisted tree-ring chronology composition system for dendrochronology is described in this thesis. Methods for tree-ring growth sequence pattern matching, hierarchical composition of master chronologies, and analytical quality control are discussed in detail and systematically implemented in the CROSSDATE program in a highly visual, graphic environment. The objective of this work is to provide dendrochronologists with a robust set of tools for comparing the relative growth patterns of tree-ring samples for purposes of dating the samples and composing new master chronologies from individual tree-ring samples and other master chronologies. This system is complementary to the TREES program, a computer-vision based tree-ring identification and measurement system developed at the University of Arizona.