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1
Ren, Dakai. "Moisture-Cure Polyurethane Wood Adhesives: Wood/Adhesive Interactions and Weather Durability." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/29866.
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This project addresses two main subjects of moisture-cure polyurethane (PUR) wood adhesives: wood/PUR interactions and structure-property behavior emphasizing on weather durability. For these purposes, one simplified model PUR (MPUR) and three more commercially significant PURs (CPURs) with different hard segment contents were prepared. Separately, an early side project involved the synthesis of a 13C and 15N double-labeled polymeric methylenebis(phenylisocyanate) (pMDI) resin; this was used for the solid-state NMR characterization of isocyanate cure chemistry in wood bondline.
MPUR and a CPUR were employed to investigate whether wood/adhesive interactions influence PUR properties. Wood interactions significantly altered PUR hard/soft domain size distribution (atomic force microscopy, AFM), thermal transition temperatures (dynamic mechanical analyses, DMA), and urethane/urea hydrogen bonds (Fourier transform infrared spectroscopy, FTIR).
The effects of hard segment content on properties of PUR prepolymers, and cured PURs (films and wood composites) were studied. Hard segment content largely influenced the PURs’ molecular weights, viscosity, penetration, thermal transitions, and hard segment hydrogen bonds, but only slightly altered the dry (unweathered) bondline toughness.
Three accelerated weathering procedures were developed to evaluate CPUR bondline weather durability through mode-I fracture testing. Both hard segment content and weathering conditions were found to significantly influence the bondline weather durability. Among these weathering procedures, only one (VPSS) was able to effectively distinguish weather durability of PUR adhesives, and therefore it was selected for detailed structure-weather durability studies. PUR weather durability was found to correlate with its moisture sensitivity and hard segment softening temperature; both were provided by water-submersion DMA. Much attention was directed to the investigation of weather-induced PUR molecular changes. FTIR studies provided evidences of post-cure, hydrolytic degradation, and variation of urethane/urea hydrogen bonds. DMA presented weathering effects on PUR thermal properties. Special efforts have been made to correlate these analytical results with PUR weather durability.
A 13C and 15N double-labeled pMDI resin was synthesized and used for solid-state NMR characterization of isocyanate cure chemistry in wood bondline, particularly to detect the evidence of urethane formation. Rotational echo double resonance (REDOR) NMR clearly revealed the formation of urethane linkages, but largely overestimated their content.Ph. D.
2
Glavas, Lidija. "Starch and Protein based Wood Adhesives." Thesis, KTH, Skolan för kemivetenskap (CHE), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-31486.
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Different native starches, modified starches and plant proteins were evaluated as wood adhesives. They were combined with different synthetic polymers in order to achieve improved adhesive properties. The study was divided into two parts: development of starch based adhesive formulations and evaluation of an existing protein based adhesive. Eight different starches and two different plant proteins were used in the first part. Starch 1 and starch 2 as well as protein 1 and protein 2 were some of the used materials. These materials were dispersed in synthetic polymers such as poly (vinyl acetate) (PVAc), styrene-butadiene rubber (SBR), poly (vinyl alcohol) (PVA), poly (acrylic acid) (PAA) and poly (ethylene-co-vinyl acetate) (EVA). Five different cross-linking agents were also tested. In the second part of the study, protein 2 was used as a renewable material. It was dispersed in dispersing media 2 and filler 1 was used. In an effort to increase the amount of renewable material in the adhesive composition, six different renewable fillers were examined. Lower pressing temperatures as well as lower amounts of cross-linking agent 1 were evaluated in order to observe their influence on the adhesive properties of the protein based adhesive. All formulations were characterized by measurement of viscosity, solid content and pH. The adhesive properties of some of the formulations in both parts of the study were characterized according to SS-EN 204:2001 and EN 14257 (WATT 91). The best results, of the starch based formulations, were obtained when starch 1 and protein 2 were dispersed in dispersing media 2 or dispersing media 7. These formulations in combination with cross-linking agents were classified as D2 and passed the criteria for heat resistance (WATT 91). However, the results were comparable with the reference sample. It was possible to replace filler 1, totally or partly, in the protein based adhesive with renewable fillers. Protein based adhesive formulations with filler 2 and filler 4, amongst others, showed improvement of the adhesive properties. These formulations passed D3 and D4 – wet criteria and almost passed D4 – boiling criteria. The amount of renewable material in the protein based adhesive was increased from ~32 % to ~56 % in the formulations that obtained the best adhesive properties. The amount of non-petrochemical material was ~67 % in all new formulations as well as in the reference sample. By decreasing the pressing temperature from 110 °C to 90 °C or by decreasing the amount of cross-linking agent 1 from 15 % to 5 %, a protein based system that passes D3 criteria can be obtained.
3
Zhang, Xuelian. "Characterization of Wood Resin-Adhesive Spray." Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/ZhangX2008.pdf.
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Yang, Xing. "Organic Fillers in Phenol-Formaldehyde Wood Adhesives." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/64999.
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Veneer-based structural wood composites are typically manufactured using phenol-formaldehyde resols (PF) that are formulated with wheat flour extender and organic filler. Considering that this technology is several decades old, it is surprising to learn that many aspects of the formulation have not been the subject of detailed analysis and scientific publication. The effort described here is part of a university/industry research cooperation with a focus on how the organic fillers impact the properties of the formulated adhesives and adhesive bond performance. The fillers studied in this work are derived from walnut shell (Juglans regia), alder bark (Alnus rubra), and corn cob (furfural production) residue.
Alder bark and walnut shell exhibited chemical compositions that are typical for lignocellulosic materials, whereas corn cob residue was distinctly different owing to the high pressure steam digestion used in its preparation. Also, all fillers had low surface energies with dominant dispersive effects. Surface energy of corn cob residue was a little higher than alder bark and walnut shell, which were very similar.
All fillers reduced PF surface tension with effects greatest in alder bark and walnut shell. Surface tension reductions roughly correlated to the chemical compositions of the fillers, and probably resulted from the release of surface active compounds extracted from the fillers in the alkaline PF medium.
It was shown that viscoelastic network structures formed within the adhesive formulations as a function of shear history, filler type, and filler particle size. Relative to alder bark and walnut shell, the unique behavior of corn cob residue was discussed with respect to chemical composition.
Alder bark and walnut shell exhibited similar effects with a decrease of adhesive activation energy. However, corn cob reside caused much higher adhesive activation energy.
Alder bark exhibited significant particle size effects on fracture energy and bondline thickness, but no clear size effects on penetration. Regarding corn cob residue and walnut shell, particle size effects on fracture energy were statistically significant, but magnitude of the difference was rather small. Classified corn cob residue fillers all resulted in a similar bondline thickness (statistically no difference) that was different walnut shell.Ph. D.
5
Wendler, Steven L. "Characterization of the wood/isocyanate bondline." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-07102009-040325/.
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Miesner, Martin. "Photodegradation of adhesives used in wood composite materials." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/2294.
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The weathering of wood composites is caused by a complex combination of chemical and mechanical effects. Wood composites such as glulam beams are increasingly being used outdoors where their service life depends to some extent on the durability of the adhesive used in the composite. Increases in the durability of adhesives used in such composite materials would prolong their service life and enable them to compete more effectively with other structural materials such as concrete and steel. This study attempted to improve our understanding of the photodegradation of adhesives and the relationship between wood and adhesive photodegradation. The effectiveness of a UV light absorber and hindered amine light stabilizer (UVA and HALS) at protecting adhesives from photodegradation was also investigated. First, the effect of adhesive type (melamine formaldehyde, epoxide, and emulsion polymer isocyanate), stabilizer and adhesive stabilizer interaction on tensile strength, weight loss and discoloration of adhesive dog-bone samples exposed in two different weatherometer devices (QUV and Xenon-arc) was examined. Structural and chemical changes of the adhesive specimens were examined using Fourier Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM). Secondly, the effects of adhesive type (melamine formaldehyde, epoxide), stabilizer and adhesive stabilizer interaction on surface roughness and discoloration of wood-adhesive-dowel samples exposed to solar radiation was examined. Profileometry and SEM was used to examine the surface of dowels in the region where they were exposed to both wood and sunlight. An epoxide adhesive (butyl glycidyl ether of bisphenol-A with polyamide) used in the aircraft industry showed outstanding resistance to weathering. The other adhesives were not as resistant to weathering, but the addition of a UVA/HALS photostabilizer to the adhesives generally increased their photostability (particularly color changes of the epoxy adhesives and weight loss of the MF adhesive). Greater degradation of adhesive samples occurred when they were exposed in a QUV weatherometer than in a Xenon-arc weatherometer. The synergistic effect of moisture and UV radiation on the degradation of adhesives may account for this observation. Adhesive dowels embedded in wood did not show greater degradation (erosion) in the region where they were exposed to both wood and sunlight. Therefore the hypotheses that wood photosensitizes adhesives could not be supported by experimental findings. Further refinement of the experimental methodology developed in this thesis would be desirable to retest this hypothesis. All of the four adhesives that were tested possessed some interesting characteristics that might make them suitable for use in glulam exposed outdoors, but out of the four the two epoxy adhesives appeared to have the greatest potential.
7
Nussbaum, Ralph. "Surface interactions of wood with adhesives and coatings /." Stockholm, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3229.
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Paris, Jesse Loren. "Carboxymethylcellulose Acetate Butyrate Water-Dispersions as Renewable Wood Adhesives." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/34644.
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Two commercial carboxymethylcellulose acetate butyrate (CMCAB) polymers, high and low molecular weight (MW) forms, were analyzed in this study. High-solids water-borne dispersions of these polymers were studied as renewable wood adhesives. Neat polymer analyses revealed that the apart from MW, the CMCAB systems had different acid values, and that the high MW system was compromised with gel particle contaminants. Formulation of the polymer into water-dispersions was optimized for this study, and proved the â direct methodâ , in which all formulation components were mixed at once in a sealed vessel, was the most efficient preparation technique. Applying this method, 4 high-solids water dispersions were prepared and evaluated with viscometry, differential scanning calorimetry, dynamic mechanical analysis, light and fluorescence microscopy, and mode I fracture testing.
Thermal analyses showed that the polymer glass transition temperature significantly increased when bonded to wood. CMCAB dispersions produced fairly brittle adhesive-joints; however, it is believed toughness can likely be improved with further formulation optimization. Lastly, dispersion viscosity, film formation, adhesive penetration and joint-performance were all dependent on the formulation solvents, and moreover, these properties appeared to correlate with each other.Master of Science
9
Lan, Ping. "Condensed tannins extraction from grape pomace : characterization and utilization as wood adhesives for wood particleboard." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0242/document.
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Les marcs de raisin issus de la viniculture constituent un gisement de ressource naturelle abondant, sous valorisé et riche en polyphénols. Une méthode d?extraction de ces tannins condensés a été développée et optimisée en vue d'une application en adhésif pour les produits dérivés du bois. Les tannins ont été caractérisés par Résonance Magnétique Nucléaire, spectroscopie Infra Rouge (FTIR), spectrométrie de masse (MALDI TOF) et Analyse Thermomécanique (TMA). Des panneaux de particules ont été fabriqués à l'aide des colles élaborées en laboratoire et testés suivant les normes françaises en vigueur, plusieurs dépassent largement les valeurs seuilsThe extraction of condensed tannins from grape pomace was examined using water medium in the presence of different bases as catalyst (NaOH, Na2CO3, NaHCO3 and Na2SO3). Two different extraction processes and the influence of 4 parameters (i.e., temperature, reaction time, chemical reagents and concentration of the chemical reagents) on the tannin extracts yields and properties were studied. The tannin fractions were characterized by Fourier transform-infrared spectroscopy, thermogravimetric analysis, carbon nuclear magnetic resonance spectroscopy and matrix assisted laser desorption ionization time of flight mass spectrometry ( MALDI-TOF ). It was demonstrated that it is possible to extract reactive tannins from grape pomace in basic medium. The tannin extracts obtained by precipitation in acidic conditions display a high phenolic content (Stiasny number higher 95%) but low water solubility and low reactivity toward formaldehyde because of the formation of catechinic acid phlobatannins during the acidification step. The tannins extracts obtained by lyophilization of the liquid, despite of their lower phenolic contents, displayed promising properties for adhesive applications. The optimum temperature of the extraction process was 100 °C, reaction time was 120 min; the best concentration of reagent was 10% (w/w). It was also shown that addition of sulphite ions during the extraction step improved the process :y the introduction of a sulfonic group through sulfitation increased both tannin solubility and reactivity as a result from the opening of the heterocyclic ring during extraction The structure of grape pomace sulfited tannin extracts did not present noticeable discrepancy exception of the ratio of the opening pyran ring which was different as a function of the catalyst used. The opening of pyran ring during the tannins extraction seem to be more important by using Na2CO3 and NaHCO3 than when using NaOH. The FT-IR bands assigned to aromatic ring vibration and carbonyl groups were stronger and no bands attributed to sulfited groups were tested detected in acidified tannins compared to lyophilized tannins. The TG2 results showed that the weight lost of these tannin extracts mainly composed of two steps. The first step starts from room temperature to 200 °C. It is attributed to the mass lost of water and some easy-degraded small low molecules. The secondly steps which is the mainly degradation step of tannin extract samples from 200 to 400 °C. The results from 13C-NMR showed that condensed tannin extracts from grape pomace were consistent with dominant procyanidin units with a minor amount of prodelphinidin units that are linked together by a C4-C8 bond. Relatively low carbonhydrate and high catechinc acid content was observed in acidified tannins compared to lyophilized tannins. It was shown by MADI-TOF experiments that grape pomace tannin extracts are mainly composed of flavoinoid oligomers up to 6 repeating units in lyophilized tannins and 10 repeating units in acidified tannins respectively, with dominant procyanidin units. A small proportion of substitution with glucose and gallic acid was detected in procyanidin units of polyflavonoid oligomers. The degree of polymerization of acidified tannins is higher than lyophilized tannins. Two different formulations (nonfortified tannin adhesive and fortified with addition of 20% of polymeric 4, 4'-diphenyl methane diisocyanate (p-MDI)) were used to press one layer wood particle board. It was shown that the nature of the extraction reagent (NaOH, Na2CO3 or NaHCO3) greatly impacts the properties of the resins and the mechanical properties of the panel internal bonding strengths. The particleboards bonded by the tannins extracted using Na2CO3 as catalyst give the best performance and were good enough to pass relevant international standard specifications for interior grade panels. Formaldehyde emission of these panels was below the European Norm requirements (<= 6.5 mg/ 100g panel)
10
Tahir, Paridah Md. "Utilisation of mangrove bark extracts in cold-setting wood adhesives." Thesis, University of Aberdeen, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327020.
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Extraction of mangrove bark with 4.0% aqueous sodium sulfite and 0.4% aqueous sodium carbonate at 100° and 2 hours gives 24-26% yields compared with extraction by water at 70° for 2 hours which gives 21%. The hot water extracts are more acidic (pH 3.6) than is the sulfite extract (pH 5.6); both are reasonably reactive toward formaldehyde (Stiasny number 70.6 using water and 85.4 using aqueous sulfite-carbonate). The 13C NMR spectra of R. mucronata shows this tannin to have phloroglucinolic A-rings with hydroxy groups at C-5 and C-7 and pyrogallolic B-rings with hydroxy groups at C-3', C-4', and C-5'. The interflavanoid linkages are C-4→C-8 and C-4→C-6. The 13C NMR spectra also indicate the presence of a considerable amount of carbohydrate which is shown to be mainly rhamnose, glucose, arabinose, and uronic acids. Sulfitation of R. mucronata bark reduces the total carbohydrate and the rhamnose extracted but increases the amount of arabinose and uronic acids. The bark storage period has significant effects on the pH and the reactivity of the aqueous tannin solution. Barks stored for <4 weeks produce higher extraction yields than those stored for > 6 weeks and contain significantly larger amount of reactive tannin and have shorter gel times. The reactivity of bark extracts towards formaldehyde can be controlled either by limiting the duration of bark storage to 4 weeks or by maintaining the aqueous tannin solution at pH <10.0. The aqueous tannin solution from R. mucronata exhibited properties such as viscosity, solubility and tackiness which were superior to those from the R. apiculata extract while the mixed R. mucronata-R. apiculata aqueous tannin solution had properties in between these. These barks could be used singly or together as a source of tannin without the bond strength of the resulting glued joints being significantly affected. The "honeymoon" bonding technique improved the bond strengths of joints made using sulfited tannin but is suitable only for tannin solutions containing > 4% aqueous sodium hydroxide. The viscosity of sulfited tannin adhesives is influenced by (a) the amount of aqueous sodium hydroxide added to the aqueous tannin solution, and (b) the lapse time, i.e. the period between the addition of sodium hydroxide to the aqueous tannin solution and the addition of phenol-resorcinol-formaldehyde (PRF) resin, hardener, and paraformaldehyde. The present study shows that with the addition of 5% w/w sodium hydroxide and at a curing temperature of 40° the sulfited tannin extracts from the bark of mangrove trees can replace about 50% w/w of the PRF resin in cold-setting wood adhesives with the production of bond strengths comparable to those produced by 100% PRF resin.
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Hale, Kristen. "The potential of canola protein for bio-based wood adhesives." Thesis, Kansas State University, 2013. http://hdl.handle.net/2097/15515.
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Master of ScienceDepartment of Biological and Agricultural Engineering
Donghai Wang
Currently, the majority of adhesives used for wood veneer, plywood, and composite applications are formaldehyde-based. Formaldehyde is derived from petroleum and natural gas, making it non-renewable and toxic. Therefore, extensive research has been conducted to develop bio-based adhesives to replace formaldehyde-based adhesives. Soy protein has shown great potential to partially replace formaldehyde adhesives, and canola protein has similar properties to soy protein. However, little research has been conducted on the feasibility of using canola protein for wood adhesive applications. The objective of this research was to study the adhesion performance of canola protein. Canola protein was modified with different chemical modifiers including sodium dodecyl sulfate (SDS), calcium carbonate (CaCO[subscript]3), zinc sulfate (ZnSO[subscript]4), calcium chloride (CaCl[subscript]2), and 2-octen-1-ylsuccinic anhydride (OSA) as well as combined chemical modifications. The wet, dry, and soak shear strengths of the adhesive formulations were determined. Viscosity testing, differential scanning calorimetry, and TEM and SEM imaging were used to characterize protein properties. Chemical modification with SDS (1%, 3%, and 5%), CaCO[subscript]3 (1%, 3%, and 5%), ZnSO[subscript]4 (1%), and OSA (2%, 3.5%, and 5%) improved the dry and soak shear strengths compared to unmodified canola protein. Canola protein modified with 3.5% OSA had improved wet, dry, and soak shear strengths. Combined chemical modification of canola protein did not show significant improvement on shear strength. Thermal modification of canola protein adhesives showed a trend of increasing shear strength with increasing press temperature. The data suggests that with further research, canola protein has potential to be used as a commercial adhesive or as an additive to formaldehyde-based adhesives to make them more environmentally-friendly.
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Stables, Christa Lauren. "Wetting and Penetration Behavior of Resin/Wood Interfaces." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/79700.
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The goal of this project was improve the fundamental understanding of the wood-resin interaction, by looking at the relationship between the resin wetting onto wood and the resulting penetration into wood lumens. Wetting was analyzed with the sessile drop method, which observed the initial contact angle and change in contact angle over 35s. Penetration was measured within each individual tracheid. The Lucas-Washburn equation analyzed the wetting and penetration by calculating the penetration and comparing it to the measured penetration.
Wetting of four resins was compared on 3 species, to improve the understanding of adhesive wetting behavior. This study agreed with previous research, that the non-aqueous resin exhibited favorable wetting and presumably better penetration than aqueous resins, with exception of urea-formaldehyde.
Wetting and penetration of pMDI was studied on 5 wood species using the Lucas-Washburn equation. The wetting behaviors exhibited grain and species effects, which had implications on the resin availability for flake/strand-based composite products. The greater surface energy of loblolly pine most likely accounted for the significantly greater penetration of loblolly pine compared to Douglas-fir. The calculated penetration, via the Lucas-Washburn equation, exceeded the measured penetration, but it was concluded that the Lucas-Washburn equation predicted penetration reasonably well.
Wetting and penetration of phenol-formaldehyde and subsequent adhesives was compared on 3 wood species using the Lucas-Washburn equation. All contact angles were unfavorable due to a skin formation. The Lucas-Washburn equation did not predict any penetration; however, penetration was observed with all systems. The findings suggest that the system was too complex for the Lucas-Washburn equation to be able to predict accurately.Master of Science
13
Phanopoulos, C. "The nature of bond formation and failure in wood-adhesive systems." Thesis, De Montfort University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374074.
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Xian, Diyan. "Effect of nanoclay fillers on wood adhesives and particle board properties." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/42266.
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The objective of this research is to investigate the effect of nanoclay additions to particleboard resins on the properties of particleboard made with those resins. Two nanoclays, Cloisite30B, a modified nanoclay and Nanofil16, an unmodified clay, were blended with the two resins used to produce particleboard: Urea Formaldehyde (UF) and Melamine Formaldehyde (MF). Coupling agent was added to nanoclays to facilitate clay dispersion into the resin. X-ray diffraction tests showed that mechanical mixing was sufficient to exfoliate Closite30B into both resin types and enable the intercalation of Nanofil116/resin mixtures.
Addition of nanoclays and coupling agents had small to severe adverse effects on resin curing: Cloisite30B slightly delayed the curing process of both UF and MF resin and reduced the reaction heat of curing, and the addition of coupling agent together with Closite30B further compounded this effect. Nanofil116 significantly delayed the curing reaction of both resins and decreased the heat of reaction. The coupling agent had a significant further detrimental effect on the resin cure.
In order to test whether nanoclays had a positive or negative effect on the adhesive strength of UF and MF resins, the shear strength of clay-modified resin were tested and compared with that of unadulterated resin. Regardless of whether coupling agent was used, the clay-modified UF resin had lower bonding strength than pure UF resin. In contrast, three kind of clay-modified MF resin had higher bonding strength then pure MF resin.
Based on these findings those MF resins which have higher shear strength were blended with furnish to fabricate particle board using different clay loading rates. Most clay treatments had no significant effect on particleboard physical or mechanical properties. The only significant improvement was for internal bond strength which increased when using either 2% Closite30B or Nanofil116 with or without coupling agent. Higher clay loading rates tended to decrease board strength properties. In conclusion, the modified Closite30B nanoclay and the unmodified Nanofil116 nanoclay had only a minor effect on improving UF and MF resin strength and the particle board properties.
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Wykle, Cody James. "Adhesive Bonding of Low Moisture Hickory Veneer with Soy-based Adhesive." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/89922.
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Low moisture veneer and regions of sapwood within hickory engineered wood flooring bonded with soy-flour adhesive are thought to be factors leading to potential performance deficiencies. The goal of this research was to gain a broader understanding of bonding low moisture hickory veneer with soy-based adhesive. Soyad® is of particular interest due to its novel cross-linking chemistry. Impacts of moisture content and wood region (heartwood versus sapwood) were analyzed with dry and wet shear bond strength tests, measurement of percent wood failure, lathe check characterization, and adhesive bondline thickness and penetration depth measurement. Impact of wood region and type (hickory versus red oak) was assessed by comparing wood buffering capacity and delamination following three-cycle water soaking.
Dry and wet shear strength values met expectations for engineered wood flooring yet percentage wood failure results were uniformly very low for all combinations of moisture levels and wood regions. In contrast, delamination following wet and dry cycling was minor and within minimum requirements for all specimens tested. The influence of moisture level, wood region and type were inconsistent; statistically significant relationships were not evident within the moisture range studied. However, different wood regions and types exhibited differing veneer buffering capacities that had potential to interfere with pH requirements of Soyad®. Additional study of buffering capacity and resin cure is recommended to determine the significance of the buffering capacity results found in this study.Master of Science
Performance issues including debonding and delamination have been reported for hickory engineered wood flooring products constructed using a soy-flour based adhesive. Sapwood regions within the composite and extremely low moisture veneer were provided by industry as possible factors that resulted in performance deficiencies. The goal of this research project was to gain a broader understanding of bonding low moisture hickory veneer with Soyad® adhesive. Soy-flour adhesive systems offer many environmental, health, and durability advantages. Soyad® is of particular interest due to its use of natural, renewable soy flour, a novel cross-linking resin, and no added formaldehyde. Test specimens were prepared using heartwood of hickory and red oak and sapwood of hickory. Analytical tests included determination of certain chemical properties of the adhesive and wood veneer, measurement of strength properties of the adhesive bond, and assessment of delamination tendencies of bonded panels following water soaking. Results indicate that moisture levels and the different growth regions and wood type had an inconsistent impact on the bond strengths yet percent wood failure was uniformly low and considered unacceptable by industry. Although this research established a foundation of basic knowledge, more information about adhesive bonding of wood with the recently developed soy based adhesives is needed to optimize the systems and provide technological advancements that lead to more efficient and safe utilization of woody materials from the forest.
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Ferguson, Christopher James. "Core-shell polymers from styrene and vinyl acetate for use as wood adhesives." Thesis, University of Canterbury. Chemistry, 2000. http://hdl.handle.net/10092/5647.
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Techniques to produce core-shell morphology have been applied to the creation of poly(vinyl acetate) emulsions for use as wood adhesives. These strategies have been used to investigate the molecular origins of some of the shortcomings of poly(vinyl acetate) adhesives, and also to attempt to enhance the properties of these widely used adhesives. A model is presented to predict the incidence of particle formation, which was used to accurately predict that the polymerisation of vinyl acetate in the presence of large polystyrene seed particles would not be possible without the formation of secondary particles. Numerous attempts were made to reduce the incidence of secondary particle formation using the mechanistic basis of the model as a guide, without success. As a result, the inverse route to core-shell morphology was used to create the desired morphology. Microscopic characteristics that favoured the formation of particles containing one centrally located polystyrene core were investigated. Transmission electron microscopy techniques were developed to allow characterisation of the morphology produced in two-stage styrene-vinyl acetate polymerizations Latices having a range of morphologies, including the desired core-shell, were subjected to a range of physical tests to evaluate their performance as wood adhesives. The information gained from this testing was used to correlate performance between tests. The results have also been explained on the basis of microscopic structure.
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Calve, Louis R. "The role of sugars in wood adhesives based on ammonium spent sulfite liquor." Thesis, University of Ottawa (Canada), 1989. http://hdl.handle.net/10393/21266.
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Zhu, Xiangwei. "Unfolding, crosslinking and co-polymerization of Camelina protein and its use as wood adhesives." Diss., Kansas State University, 2017. http://hdl.handle.net/2097/35420.
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Doctor of PhilosophyDepartment of Grain Science and Industry
X. Susan Sun
Oilseed protein is a promising renewable source to be used as the replacement of petroleum-based materials for adhesion purpose, and it has drawn increasing attention since soy-based adhesives were developed for wood glues. However, soy protein comprises a portion of humans’ diets, thereby creating competition between utilization of soy protein for protein-based products or human food. Therefore, alternative bio-resources must be discovered. Proteins from camelina sativa provide such potential. Similar to other protein-based polymers, low mechanical strength and poor water resistance are the major drawbacks limiting camelina protein’s further applications. In this research, camelina protein (CP) was modified by unfolding, crosslinking, and co-polymerization treatment for improved flow-ability, adhesion properties and water resistance, which facilitates the industrialization of camelina as an alternative to soy-based adhesives. The physicochemical properties and microstructures of CP were also investigated. To increase the reactivity of CP adhesive, the first step is to denature the folded structure of native proteins. Camelina protein was extracted from defatted camelina meal through alkali solubilization and acid precipitation and modified with varying amount of NaHSO₃ (0-12% of the protein dry base) and Gdm.Cl (0-250% of the protein dry base). NaHSO₃ treatment broke the disulfide bonds of the CP and thus increased its free sulfhydryl content and surface hydrophobicity. As NaHSO₃ concentration increased, the viscosity, elastic modulus (G') and water resistant of NaHSO₃-modified camelina protein (SMCP) dispersion decreased, and the protein became hydrophobic. Gdm.Cl treatment broke the CPI’s hydrogen bonds but decreased their surface hydrophobicity. Similarly, viscosity, G', and water resistant of Gdm.Cl-modified camelina protein (GMCP) dispersions decreased as Gdm.Cl increased and protein became to aggregate. The reducing effect of NaHSO₃ was more obvious than Gdm.Cl to disrupt CPI’s intermolecular protein interaction but less obvious than Gdm.Cl to reduce the viscosity and water resistant. To further increase the CP’s water resistance, a coupling agent, Ethyl-3-(3-dimethyl-aminopropyl-1-carbodiimide) (EDC), was applied to stabilize the protein structure by crosslinking the free carboxyl groups and amino groups. The cross-linked CP exhibited increased molecular weight and particle size. Microstructures of modified CP also became rigid and condensed. Accordingly, CP’s increased intermolecular protein interaction resulted in its higher elastic modulus, viscosity and water resistance. The ultrasound pretreatment further increased the crosslink degree of CP, which resulted in protein’s increased aggregation behaviors and compact micro-structures. Consequently, the elastic modulus, viscosity, and water resistance of CP increased accordingly. Copolymerization with hydrophobic enhancers was also an effective method to improve CP’s water resistance. In this study, kraft lignin was oxidized by H₂O₂ and then copolymerized with CP as wood adhesives, which exhibited increased wet strength. In the presence of ultrasound irradiation, the H₂O₂-depolymerized kraft lignin exhibited reduced particle size, thermal stability and increased content of hydroxyl groups. Fluorescence spectroscopy analysis revealed that after coupling with pristine or de-polymerized lignin, CP exhibited increased hydrophobicity due to lignin’s increased reactivity with camelina protein. Accordingly, the water resistance of CP-based adhesives improved. In the optimized condition, when CP was copolymerized with ultrasound-induced oxidized lignin, it had increased wet shear adhesion strength from 0.28 MPa to 1.43 MPa, with wood panels passing the three-cycle water soaking test.
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Alvarez, Gloria Amelia. "Evaluation of the Ability of Adhesives to Substitute Nails in Wooden Block Pallets." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/99422.
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The most common fastening technique that is used to connect the components of wooden pallets together are helically or annularly threaded pallet nails. Pallet nails create a strong durable connection and increase manufacturing efficiency for a low cost. However, nails can also cause iron staining, wood splitting, and when exposed can cause product damage or personnel injury. Using adhesives could be a solution to these problems, but only if the adhesives� strength and durability is comparable or higher than nails. The objective of the study was to investigate the tensile and shear strength of pallet connections secured using commercially available wood adhesives and compare their performance to pallet connections secured using common pallet nails.
The lowest pre-compression pressure resulted in the best tension and shear performance for a solvent based construction adhesive (SBCA). The pre-compression pressure did not have any practical effect on the performance of the two-part emulsion polymer isocyanate (EPI) adhesive. Samples made with the solvent based construction adhesive (SBCA) had greater strength and energy at failure than nailed samples. Meanwhile, the samples made with the two-part emulsion polymer isocyanate (EPI) adhesive had equal or greater strength than nailed samples, except for during the tension parallel to the grain tests in which they had equal or lower strength.MS
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Riedlinger, Darren Andrew. "Characterization of PF Resol/Isocyanate Hybrid Adhesives." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/31366.
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Water-based resol phenol formaldehyde, PF, and organic polymeric methylenebis(phenylisocyanate), pMDI, are the two primary choices for the manufacture of exterior grade wood-based composites. This work addresses simple physical blends of pMDI dispersed in PF as a possible hybrid wood adhesive. Part one of this study examined the morphology of hybrid blends prepared using commercially available PF and pMDI. It was found that the blend components rapidly reacted such that the dispersed pMDI droplets became encased in a polymeric membrane. The phase separation created during liquid/liquid blending appeared to have been preserved in the cured, solid-state. However, substantial interdiffusion and copolymerization between blend components also appeared to have occurred according to measured cure rates, dynamic mechanical analysis, and atomic force microscopy. In the second part of this study a series of PF resins was synthesized employing the so-called â split-cookâ method, and by using a range of formaldehyde/phenol and NaOH/phenol mole ratios. These neat PF resins were subjected to the following analyses: 1) steady-state flow viscometry, 2) free formaldehyde titration, 3) non-volatile solids determination, 4) size exclusion chromatography, 5) quantitative solution-state 13C nuclear magnetic resonance, NMR, 6) differential scanning calorimetry, 7) parallel-plate oscillatory cure rheology, and 8) dielectric spectroscopy. The neat PF analytical results were unremarkable with one exception; NMR revealed that the formaldehyde/phenol mole ratio in one resin substantially differed from the target mole ratio. The neat PF resins were subsequently used to prepare of series of PF/pMDI blends in a ratio of 75 parts PF solids to 25 parts pMDI solids. The resulting PF/pMDI blends were subjected to the following analyses: 1) differential scanning calorimetry, 2) parallel-plate oscillatory cure rheology, and 3) dielectric spectroscopy. Similar to what was inferred in part one of this study, both differential scanning calorimetry (DSC) and oscillation cure rheology demonstrated that cure of the PF continuous phase was substantially altered and accelerated by pMDI. However within actual wood bondlines, dielectric analysis detected little variation in cure speed between any of the formulations, both hybrid and neat PF. Furthermore, the modulated DSC curing experiments detected some latent reactivity in the hybrid system, both during initial isothermal curing and subsequent thermal scanning. The latent reactivity may suggest that a significant diffusion barrier existed between blend components, preventing complete reaction of hybrid blends even after thermal scanning up to 200 °C. Part three of this work examined the bonded wood mode-I fracture performance of hybrid resins as a function of the resol formaldehyde/phenol ratio and also the alkali content. A moderate increase in unweathered fracture toughness was observed for hybrid formulations relative to neat PF. Following accelerated weathering, the durability of the hybrid blends was promising: weathered hybrid toughness was equivalent to that of weathered neat PF. While the resol F/P ratio and alkali content both influenced hybrid fracture toughness, statistical modeling revealed interaction between these variables that complicated result interpretation: the influence of hybrid alkali content depended heavily on each formulationâ s specific F/P ratio, and vice versa.Master of Science
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Janová, Petra. "Adhezní spolupůsobení lepidla s konstrukčním dřevem." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2020. http://www.nusl.cz/ntk/nusl-409760.
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This labor is based on penetration of adhesives into a wood cell walls. It focuses mainly on adhesives that are currently used for construction purposes. It also contains a methodics of selecting adhesives and wood, which will be used for glued joints and summarizes the methods used for detect these adhesives in the wood cell wall. It experimentally verifies the appropriate selection of the dye-solvent combination used in the adhesive.
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Zheng, Jun. "Studies of PF Resole / Isocyanate Hybrid Adhesives." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/25960.
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Phenol-formaldehyde (PF) resole and polymeric diphenylmethane diisocyanate (PMDI) are two commonly used exterior thermosetting adhesives in the wood-based composites industry. There is an interest in combining these two adhesives in order to benefit from their positive attributes while also neutralizing some of the negative ones. Although this novel adhesive system has been reportedly utilized in some limited cases, a fundamental understanding is lacking. This research serves this purpose by investigating some of the important aspects of this novel adhesive system.
The adhesive rheological and viscometric properties were investigated with an advanced rheometer. The resole/PMDI blends exhibited non-Newtonian flow behavior. The blend viscosity and stability were dependent on the blend ratio, mixing rate and time. The adhesive penetration into wood was found to be dependent on the blend ratio and correlated with the blend viscosity. By using dynamic mechanical analysis, the blend cure speed was found to increase with the PMDI content. Mode I fracture testing of resole/PMDI hybrid adhesive bonded wood specimens indicated the dependence of bondline fracture energy on the blend ratio. The 75/25 PF/PMDI blend exhibited a high fracture energy with a fast cure speed and processable viscosity. Exposure to water-boil weathering severely deteriorated the fracture energies of the hybrid adhesive bondlines.
More detailed chemistry and morphological studies were performed with cross-polarization nuclear magnetic resonance and 13C, 15N-doubly labeled PMDI. A spectral decomposition method was used to obtain information regarding chemical species concentration and relaxation behavior of the contributing components within the major nitrogen resonance. Different urethane concentrations were present in the cured blend bondlines. Water-boil weathering and thermal treatment at elevated temperatures (e.g. > 200°C) caused reduced urethane concentrations in the bondline. Solid-state relaxation parameters revealed a heterogeneous structure in the non-weathered blends. Water boil weathering caused a more uniform relaxation behavior in the blend bondline.
By conducting this research, more fundamental information regarding the PF/PMDI hybrid adhesives will become available. This information will aid in the evaluation of, and improve the potential use of PF/PMDI hybrid adhesives for wood-based composites.Ph. D.
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Vrazel, Matthew Eric. "The effects of species, adhesive type, and cure temperature on the strength and durability of a structural finger joint." Thesis, Mississippi State : Mississippi State University, 2002. http://library.msstate.edu/etd/show.asp?etd=etd-05152002-122630.
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Brown, Nicole Robitaille. "Understanding the Role of N-Methylolacrylamide (Nma) Distribution in Poly(Vinyl Acetate) Latex Adhesives." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/26446.
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This work addresses the distribution of N-methylolacrylamide (NMA) units in crosslinking poly(vinyl acetate) (PVAc) adhesives. In this case, distribution refers to the three potential locations of polymerized NMA units in a latex: the water-phase, the surface of polymer particles, and the core of the polymer particles. The objective is to identify the distribution of NMA in three latices and to determine whether NMA distribution correlates with durability related performance. NMA distribution was studied via a series of variable temperature solution NMR experiments, while the durability-related performance was studied via mode I fracture mechanics tests.
Studying the distribution of NMA required the use of isotopically labeled NMA. Both 15N-NMA and 13C, 15N-NMA were synthesized. Three NMA/vinyl acetate (VAc) latices were prepared. The NMA feed strategy was varied during each of the three emulsion copolymerizations. Latex characterization methods including differential scanning calorimetry (DSC), rheometry, particle size analysis, and scanning electron microscopy (SEM) were used to study the three latices.
The solution NMR method to identify NMA distribution was performed on untreated latices and on washed latices. Washing techniques included membrane dialysis and centrifugation. Results revealed that the three latices had different NMA distributions, and that the distributions were related to the expected differences in microstructure. Latex 3 had ~ 80% core-NMA, while Latex 2 had ~ 80% surface-NMA. Latex 1 had a high proportion of surface-NMA (~60%), but also had the highest proportion of water-phase NMA (~ 20%). This high proportion of water-phase NMA could be responsible for the unique morphology Latex 1 exhibited in SEM studies.
Mode I opening fracture mechanics studies were used to study adhesive performance. Specimens were analyzed after exposure to accelerated aging treatments. Latex 2 and Latex 3 exhibited very similar results, despite having very different NMA distributions. All three latices showed good durability related performance. In Latex 2 and Latex 3, the critical strain energy release rates (Gc) after accelerated aging treatments were statistically the same as the Gc of the control specimens. The most interesting finding was that the Latex 1 Gc values were significantly higher after accelerated aging. Latex 1 also had the highest proportion of water-phase NMA. Bondline images and SEM micrographs both indicated that the integrity of Latex 1 was least affected by the accelerated aging treatments.Ph. D.
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Silva, Cátia da Costa e. "Análise teórica e experimental de vigas de madeira de seção transversal \"I\" para uso em fôrmas para concreto." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-14072010-091217/.
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Devido à importância da madeira na construção civil e a preocupação com o impacto ambiental, a engenharia passou a se preocupar com a racionalização de seu uso por meio da apresentação de produtos engenheirados, buscando melhorar as propriedades técnicas das construções em madeira. Novos modos de manufatura foram introduzidos, principalmente no campo da engenharia estrutural, fazendo com que se desenvolvessem elementos comprovadamente superiores em suas propriedades físico-químicas e econômicas a outros normalmente usados. Neste trabalho foram avaliadas as propriedades de resistência e elasticidade de vigas de madeira de seção transversal \"I\", utilizadas na sustentação de painéis de fôrmas para concreto armado e em obras civis estruturais, incluindo as emendas de mesas e alma-mesa utilizadas em sua fabricação, por meio de ensaios de flexão e cisalhamento na linha de cola. Essas vigas são comercialmente chamadas de H2O devido a sua altura de 20 centímetros, sendo compostas de mesa em madeira serrada, almas em compensado sarrafeado, compensado laminado ou madeira serrada, e dois tipos de adesivos o de poliuretano e o de resorcinol-formol. As análises visaram comprovar a eficiência e viabilidade técnica da fabricação e utilização destes materiais nestas vigas. A configuração de viga H2O que apresentou os melhores resultados comparativamente com o mínimo exigido nos ensaios especificados pela norma européia EN 13377:2002 foi a composta por alma de compensado, emenda dentada e colada com o adesivo de Resorcinol-Formol.Due to the importance of wood in construction and the concern about the environmental impact, engineers have worried about the rationalization of its use through the development of engineered products, seeking the improvement of the technical properties. In this study, the I-beams built with reforestation wood were used for concrete formwork purpose. Their mechanical properties and the connections between flanges and web used in its manufacture were evaluated by means of bending tests and shear in the glue line. These beams are commercially called H2O. The flanges were made from Pinus Oocarpa, the webs were made from laminated plywood, block plywood, and Pinus Oocarpa, and two types of adhesives were used: polyurethane and resorcinol-formaldehyde. The H2O beam configuration showed the best results compared to the minimum required by European standard EN 13377:2002 was with the flange made from lumber, glued with resorcinol-formaldehyde and the web of laminated plywood.
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Sterley, Magdalena. "Characterisation of green-glued wood adhesive bonds." Doctoral thesis, Linnéuniversitetet, Institutionen för teknik, TEK, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-18606.
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The gluing of unseasoned wood, called green gluing, is a relatively new sawmill process, implying a radically changed order of material flow in the production of value-added wood-based products. It facilitates the enhancement of raw material recovery and value yield by integrating defect elimination and gluing already before kiln drying. The present study evaluates green glued adhesive bonds in flatwise glued beams and finger joints. The main part of this work deals with green gluing using a moisture curing polyurethane adhesive (PUR). Standardised test methods and specially designed, small scale, specimens were used for the determination of the strength, fracture energy and the ductility of both dry- and green glued bonds in tension and in shear. Using the small scale specimens it was possible to capture the complete stress versus deformation curves, including also their unloading part. An optical system for deformation measurement was used for the analysis of bond behaviour. The influence of moisture content during curing and temperature after curing on the adhesive chemical composition and on the mechanical properties was investigated. Furthermore, the moisture transport through the adhesive bond during curing was tested. Finally, microscopy studies were performed for analysis of bond morphology and fracture. The results show that two significant factors influence the shear strength of green glued bonds: wood density and adhesive spread rate. Bonds which fulfil the requirements according to EN 386 could be obtained within a wide range of process parameters. The small specimen tests showed that green glued PUR bonds can reach the same strength and fracture energy, both in shear and in tension, as dry glued bonds with the same adhesive amount. The local material properties of the bonds could be determined, thanks to the failure in the tests taking place within the adhesive bond itself and not in the wood. Following process factors were shown to cause lower bond strength: a) a low adhesive spread rate, b) high pressure and c) short pressing time in combination with low wood density and high moisture content. Moreover, the heat treatment of the cured PUR adhesive during drying influenced the chemical composition of the adhesive, providing for higher strength, stiffness and Tg of the adhesive, caused by an increased amount of highly ordered bidentate urea.
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SILVA, Gilmar Correia. "Qualidade de pain?is aglomerados produzidos com adesivos ? base de lignosulfonato e ur?ia-formalde?do." Universidade Federal Rural do Rio de Janeiro, 2015. https://tede.ufrrj.br/jspui/handle/jspui/1505.
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This study aimed to evaluate the quality of panels Pinus caribaea var caribaea produced from lignosulfonato based adhesive (LS), urea formaldehyde (UF) and mixtures thereof, variations in time and pressing temperature. For that, were determined the physical and chemical properties of wood and adhesives, the chemical composition of the LS and its chemical bonds by infrared spectroscopy (IR) and nuclear magnetic resonance (NMR), and pure in composition with different catalysts , the substitution effect of different percentages of UF by LS in the production of panels on the technological properties. They were also produced panels with modified LS acid. The predetermined nominal density of the panels was 0,70g/cm?. LS used in solid form was diluted to 45% in distilled water. The production of the panels was performed in three steps by varying the press temperature (140, 160 and 180?C). In the first step was applied at 140?C for composite panels 100% UF and thereafter was to be replaced by LS in the proportions of 20, 40, 60, 80 and 100%. In a second step, the first step three treatments with results from inferior mechanical properties were tested at temperatures of 160 to 180?C. In the third stage they were produced composite panels only with LS adhesive and acid in the previous three temperatures. The results of basic and apparent wood density were 0,54 and 0,60g/cm?, respectively. The extractive content of the wood was 1,80%, the macromolecular components present in the cell wall of the wood (cellulose, hemicellulose and lignin) followed the standard for the species, and pH and buffering capacity of the timber. NMR analysis showed the same pattern for lignin derivatives in their chemical bonds. Regarding the physical properties of the boards produced at 140?C, smaller percentages of thickness swelling and water absorption were checked in particleboards produced with 100% UF. For mechanical properties, no significant difference occurred between the panels made with 100% UF panels and modified with up to 40% LS. The panels produced with temperatures of 160 and 180?C generate similar results and in most higher in temperature at 180?C. Since the panels produced with LS and acid had generally improved in all properties, especially those with higher temperature
O presente trabalho teve como objetivo geral avaliar a qualidade de pain?is aglomerados de Pinus caribaea var. caribaea produzidos a partir de adesivo ? base de lignosulfonato (LS), ureia-formalde?do (UF) e suas misturas, sob varia??es de tempo e temperatura de prensagem. Para tanto, foram determinadas as propriedades f?sicas e qu?micas da madeira e dos adesivos, a composi??o qu?mica elementar do LS e suas liga??es qu?micas por meio da espectroscopia de infravermelho (IV) e resson?ncia magn?tica nuclear (RMN), puro e em composi??o com diferentes catalisadores, o efeito da substitui??o de diferentes porcentagens de UF por LS na produ??o dos pain?is sobre as propriedades tecnol?gicas. Tamb?m foram produzidos pain?is com LS modificados com ?cido. A densidade nominal preestabelecida dos pain?is foi de 0.70 g/cm?. O LS utilizado na forma s?lida foi dilu?do a 45% em ?gua destilada. A produ??o dos pain?is foi realizada em tr?s etapas variando a temperatura de prensagem (140, 160 e 180?C). Na primeira etapa foi aplicada a temperatura de 140?C para pain?is compostos com 100% de UF e a partir da? houve a sua substitui??o por LS nas propor??es de 20, 40, 60, 80 e 100%. Numa segunda etapa, tr?s tratamentos da primeira etapa com resultados de propriedades mec?nicas inferiores foram testados nas temperaturas de 160 e 180?C. Na terceira etapa foram produzidos pain?is compostos apenas com o adesivo LS e ?cido nas tr?s temperaturas anteriores. Os resultados da densidade b?sica e aparente da madeira foram de 0,54 e 0,60g/cm?, respectivamente. O teor de extrativos da madeira foi de 1,80%, os componentes macromoleculares presentes na parede celular da madeira (celulose, hemicelulose e lignina) seguiram o padr?o para a esp?cie, assim como o pH e a capacidade tamp?o da madeira. A an?lise de RMN mostrou o mesmo padr?o para derivados de lignina em suas liga??es qu?micas. Em rela??o ?s propriedades f?sicas dos pain?is produzidos a 140?C foram verificadas porcentagens menores de inchamento em espessura e absor??o de ?gua nos pain?is produzidos com 100% de UF. Para as propriedades mec?nicas, os tratamentos que tiveram composi??o modificada com at? 40% de LS, n?o apresentaram diferen?a significativa com o tratamento produzido com 100% de UF. Os pain?is produzidos com temperaturas de 160 e 180?C geraram resultados similares e na maioria superiores na temperatura de 180?C. J? os pain?is produzidos com LS e ?cido apresentaram em geral, melhoria em todas as propriedades, com destaque para aqueles com maior temperatura.
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Blyberg, Louise. "Timber/Glass Adhesive Bonds for Structural Applications." Licentiate thesis, Linnéuniversitetet, Institutionen för teknik, TEK, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-14956.
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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.
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Nordqvist, Petra. "Exploring the Wood Adhesive Performance of Wheat Gluten." Doctoral thesis, KTH, Ytbehandlingsteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-94883.
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The increasing environmental concern has reawakened an interest in materials based on renewable resources as replacement for petroleum-based materials. The main objective of this thesis was to explore plant proteins, more specifically wheat gluten, as a binder in wood adhesives intended for typical solid wood applications such as furniture and flooring. Alkaline and acidic dispersions of wheat gluten were used as wood adhesives to bond together beech wood substrates. Soy protein isolate was used as a reference. The tensile shear strengths of the substrates were measured for comparison of bond strength and resistance to cold water. AFM in colloidal probe mode was used to investigate nanoscale adhesion between cellulose and protein films. Wheat gluten was divided into the two protein classes; glutenins and gliadins, and their adhesive performance was compared with that of wheat gluten. Heat treatment and mild hydrolysis were investigated as means for improving bonding performance of wheat gluten. The treated wheat gluten samples were analysed by SE-HPLC and 13C-NMR to correlate molecular size distribution and structural changes with bonding performance. Soy protein isolate is superior to wheat gluten, especially in regards to water resistance. However, the bond strength of wheat gluten is improved when starved bond lines are avoided. The AFM analysis reveals higher interfacial adhesion between soy protein isolate and cellulose than between wheat gluten and cellulose. These results partly explain some of the differences in bonding performance between the plant proteins. Soy protein isolate contains more polar amino acid residues than wheat gluten and possibly interacts more strongly with cellulose. Furthermore, the bond performances of wheat gluten and glutenin are similar, while that of gliadin is inferior to the others, especially regarding water resistance. The extent of penetration of the dispersions into the wood material has a large impact on the results. The bonding performance of gliadin is similar to the others when over-penetration of the dispersion into the wood material is avoided. Moreover, the bond strength of the wheat gluten samples heated at 90°C was in general improved compared to that of wheat gluten. A small improvement was also obtained for some of the hydrolyzed wheat gluten samples (degree of hydrolysis: 0-0.6 %). The improvements in bonding performance for the heat treated samples are due to polymerization, while the improvements for the hydrolyzed samples are due to denaturation. The 13C-NMR analysis of the treated samples confirms some degree of denaturation.QC 20120514
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Khan, Shaheed. "Failure of aspen wood/resorcinol-formaldehyde adhesive bond." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0035/NQ65462.pdf.
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Ni, Jianwen. "Molecular investigation of the wood/pMDI adhesive bondline." Diss., This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-10042006-143913/.
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Schmitz, John F. "Comparison of soy-flour hydrolysates for wood adhesive systems." [Ames, Iowa : Iowa State University], 2006.
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Laborie, Marie-Pierre Genevieve. "Investigation of the Wood/Phenol-Formaldehyde Adhesive Interphase Morphology." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/26411.
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This work addresses the morphology of the wood/ Phenol-Formaldehyde (PF) adhesive interphase using yellow-poplar. In this case, morphology refers to the scale or dimension of adhesive penetration into wood. The objective is to develop methods for revealing ever smaller levels of wood/resin morphology. Dynamic techniques that are commonly utilized in polymer blend studies are investigated as potential methods for probing the wood/ adhesive interphase morphology. These are Dynamic Mechanical Analysis (DMA) and solid state NMR using CP/MAS. PF resin molecular weight is manipulated to promote or inhibit resin penetration in wood, using a very low or a very high molecular weight PF resin.
With DMA, the influence of PF resin on wood softening is investigated. It is first demonstrated that the cooperativity analysis according to the Ngai coupling model of relaxation successfully applies to the in-situ lignin glass transition of yellow-poplar and spruce woods. No significant difference in intermolecular coupling is detected between the two woods.
It is then demonstrated that combining simple DMA measurements with the cooperativity analysis yields ample sensitivity to the interphase morphology. From simple DMA temperature scans, a low molecular weight PF (PF-Low) does not influence lignin glass transition temperature. However, the Ngai coupling model of relaxation indicates that intermolecular coupling is enhanced with the low molecular weight PF. This behavior is ascribed to the low molecular weight PF penetrating lignin on a nanometer scale and polymerizing in-situ.
On the other hand, a high molecular weight resin with a broad distribution of olecular weights (PF-High) lowers lignin glass transition temperature dramatically. This plasticizing effect is ascribed to a small fraction of the PF resin being low enough in molecular weight to penetrate lignin on a nanoscale, but being too dispersed for forming a crosslinked network.
With CP/MAS NMR, intermolecular cross-polarization experiments are found unsuitable to probe the angstrom scale morphology of the wood adhesive interphase. However, observing the influence of the PF resins on the spin lattice relaxation time in the rotating frame, HT1r, and the cross-polarization time (TCH) is useful for probing the interphase morphology. None of the resins significantly affects the cross-polarization time, suggesting that angstrom scale penetration does not occur with a low nor a high molecular weight PF resin. However, the low molecular weight PF substantially modifies wood polymer HT1r, indicating that the nanometer scale environment of wood polymers is altered. On the other hand, the high molecular weight PF resin has no effect on wood HT1r. On average, the high molecular weight PF does not penetrate wood on a nanometer scale. Interestingly, the low molecular weight PF resin disrupts the spin coupling that is typical among wood components. Spin coupling between wood components is insensitive to the high molecular weight PF. Finally, it is noteworthy that the two PF resins have significantly different T1r 's in-situ. The low molecular weight resin T1r lies within the range of wood relaxations, suggesting some degree of spin coupling. On the other hand, the T1r of the high molecular weight PF appears outside the range of wood relaxations. Spin coupling between the high molecular weight resin and wood components is therefore inefficient.
The CP/MAS NMR and DMA studies converge to identify nanometer scale penetration of the low molecular weight PF in wood. On the other hand, the high molecular weight PF resin forms separate domains from wood, although a very small fraction of the PF-High is able to penetrate wood polymers on a nanoscale.Ph. D.
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Mosher, Bryan C. "Failure Prediction of Adhesively Bonded Hardboard Doorskin Joints." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/42867.
Full textAbstract:
Wood and wood based composites such as hardboard have become very common materials for use in non-structural applications, which include pre-finished paneling, siding, exterior trim, furniture, and door skins. This thesis describes the results of a study of the failure of hardboard door skins. Forces applied during manufacture load the door skins in bending, and in some cases cause a split at the edge of the hardboard. A finite element model as well as a closed form solution based on mechanics of materials were developed to analyze the stresses and deformations of the door skin/stile assembly so that stresses could be predicted for various stile widths and loading conditions. The wood members that make up the frame along the perimeter of the doors, or stiles, were modeled as orthotropic and their properties were selected from available literature. The hardboard was modeled as transversely isotropic, and its properties were determined experimentally. The closed form solution developed can be used to determine the critical geometry for different combinations of hardboard thickness and adhesive joint stiffness. It predicts that as the stile width decreases, the point of maximum deflection, and greatest stresses, moves toward the outside edge of the panel. The ability to predict the critical stile width, or the stile width below which the maximum deflection and stress occurs at the outside edge of the panel, allows one to design the joint to be able to withstand specific loadings and prevent unwanted delamination of the hardboard during manufacture.Master of Science
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Alexander, Deen Fusi. "Synthetic Functionalization of Colloidal Lignin Particles for Wood Adhesive Applications." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-283138.
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Functionalizable spherical colloidal lignin particles (CLPs) represent a valuable asset for the valorization of lignin side-streams from the pulp industry. The spherical structure allows for the circumvention of the heterogeneous and poorly dispersible structure of the biopolymer. However, organic solvents and alkaline media degrade the particle structure and dissolve the polymers due to their chemical nature and solubility. The solvents will alter the aggregated polymers into irregular shapes that would correspond to inconsistent physicochemical properties. Then, the material will become unusable for advanced material applications, namely wood adhesives. In this study, a replicable process to yield pH ca. 12 stable CLPs for wood adhesives or further functionalization for other advanced material applications was developed and optimized. Lignin was functionalized with cross-linkers, glyoxal or formaldehyde, and selfassembled into spherical structures in the micro emulsification of the organic solution. The formed colloids were partially rotary evaporated to retain organic solvents within the colloidal structures, and then be cured at 73-76 °C until pH stable and further functionalized for advanced material applications. The functionalization with glyoxal was pursued further for its possibly increased reactivity and the health concerns associated with formaldehyde. The process requires the addition of glyoxal to lignin in an acidic organi cmedia at ambient temperature, and the solution to react at 64 °C. Glyoxal is likely added to the polymer structure in its hydrated and dimerized form, and its attachment to lignin should be analyzed through the behavior of glyoxal in different media. The formed colloids were rotary evaporated to an organic solvent content of 60 wt. % of the spheres to allow the occurrence of the curing reaction. These materials were finally cured by thermosetting them at 73-76 °C until pH stable. The particles can be cured with base-catalysis through the controlled addition of the base NaOH(aq). However, the mode and rate of addition of the catalyst are critically important for a nondegradative infusion of a base into solvent present ot removed particles without morphological changes. Further procedural improvement and larger batches are necessary to conduct CLP adhesive experiments.Funktionaliserbara sfäriska kolloidala ligninpartiklar (CLP) är en värdefull tillgång för valorisering av ligninsidoströmmar från massaindustrin. Den sfäriska strukturen reducerar effekten av den heterogena och dåligt dispergerbara biopolymeren. Organiska lösningsmedel och alkaliska medier försämrar emellertid partikelstrukturen och löser upp polymererna på grund av deras kemiska natur och löslighet. Lösningsmedel kommer att resultera i att de aggregerade polymererna antar oregelbundna former vilket skulle resultera i inkonsistenta fysikalisk-kemiska egenskaper. Därigenom blir materialet oanvändbart för avancerade materialapplikationer, såsom t ex trälim. I denna studie, utvecklades och optimerades en reproducerbar process för att ge pH ca. 12 stabila CLP för trälim eller ytterligare funktionalisering för andra avancerade materialapplikationer. Lignin funktionaliserades med tvärbindare, glyoxal eller formaldehyd och självorganiserades till sfäriskas trukturer genom mikroemulgering av organfasen. De bildade kolloiderna indunstades delvis roterande för att bibehålla det organiska lösningsmedlet i de kolloidala strukturerna och härdades sedan vid 73-76 ° C tills pH-stabilitet och funktionaliserades ytterligare för avancerade materialapplikationer. Funktionaliseringen med glyoxal utfördes också för att reaktiviteteten och begränsa de hälsoproblem som är förknippade med formaldehyd. Förfarandet kräver tillsats av glyoxal till lignin i ett surt organiskt medium vid rumstemperatur för att sedan reageras vid 64 ° C. Glyoxal i dess hydratiserade och dimeriserade form adderas sannolikt till polymeren, och dess kemiska inbindning till lignin kan analyseras genom att undersöka glyoxal uppförande i olika medier. De bildade kolloiderna indunstades till ett organiskt lösningsmedelsinnehåll av 60 viktprocent för att möjliggöra härdning. Dessa material härdades slutligen genom värmehärdning vid 73-76 ° C tills pH var stabilt. Partiklarna kan härdas med baskatalys genom kontrollerad tillsats av basen NaOH (aq). Emellerti där sättet och tillsatshastigheten för katalysatorn kritiskt viktigt. Ytterligare processförbättringar och större satser är nödvändiga för att genomföra CLP-limexperiment.
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Gao, Tian. "Mode-I Fracture in Bonded Wood: Studies of Adhesive Thermal Stability, and of the Effects of Wood Surface Deactivation." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/31697.
Full textAbstract:
This work included two separate studies; the common theme in each was the use of mode-I fracture testing to evaluate wood adhesion.
In the first study, mode-I fracture testing was used to compare the thermal stability of polyurethane (PUR) and resorcinol-formaldehyde (RF) wood adhesives. Bonded specimens for both adhesives were subjected to prolonged thermal exposure, and fracture testing was subsequently conducted after re-equilibration to standard test conditions. It was found that both PUR and RF suffered a significant fracture energy loss after heat treatment, and that RF was more thermally stable than PUR, as expected. However, both adhesives suffered significant thermal degradation, and fracture testing did not distinguish the RF system as being clearly superior to PUR. Dynamic mechanical analysis (DMA) was also used to analyze and compare the thermal softening of PUR and RF in terms of the decline in storage modulus. DMA results indicated that PUR specimens suffered greater stiffness loss due to simple thermal softening. Because fracture testing indicated that both adhesives suffered significant degradation, the DMA results suggested that the generally superior fire resistance of RF adhesives is born from greater high temperature stiffness; whereas the more compliant PUR suffers greater immediate softening during thermal exposure. In other words, both systems suffer from thermal degradation, but the more highly cross-linked RF system suffers less thermal softening and therefore maintains a greater load carrying capacity during fire exposure.
In the second study, mode-I fracture testing was used to test the effects of wood surface thermal deactivation (surface energy reduction) on the adhesion between southern pine wood (Pinus spp.) and polyethylene (PE). Pine specimens were progressively surface deactivated by 185°C heat treatments for periods of 5, 15, and 60 minutes. Control and deactivated pine laminae were subsequently hotpressed/bonded using PE film as the adhesive. Mode-I fracture testing was conducted under the assumption of linear elasticity, however load/displacement test curves suffered from a severe degree of nonlinearity believed to be caused by PE bridging behind the advancing crack tip. Instead of applying a nonlinear data analysis, a standard linear elastic analysis was conducted and deemed acceptable for comparative purposes within this study. Under dry conditions (unweathered specimens), 5 and 15 minute thermal treatments resulted in progressively worse adhesion (lower fracture energies) when compared to control surfaces; but the 60 minute heat treatment improved adhesion relative to 5 and 15 minute treatments, and showed a trend of improving adhesion as surface deactivation became more extreme. Simulated-weather resistance was also studied and it was determined that the highest degree of surface deactivation slightly improved weather durability in comparison to control surfaces. Overall, the findings here were similar to those in a previously published work- thermal deactivation of wood surfaces shows promise as a method to improve adhesion between wood and nonpolar polyolefins.Master of Science
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Jacobs, William P. V. "Performance of Pressure Sensitive Adhesive Tapes In Wood Light-Frame Shear Walls." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/32795.
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The performance of connections and full-scale shear walls constructed with acrylic foam pressure sensitive adhesive (PSA) tape is the focus of this thesis. The objectives of this study were first to investigate the bonding characteristics of adhesive tape to wood substrates and then to expand this investigation to cover adhesive-based shear walls subjected to high wind and seismic loadings. A total of 287 monotonic connection tests and 23 reversed cyclic wall tests were performed to achieve these objectives. Connection tests were performed in accordance with ASTM D 1761-88 (2000), and walls were tested using the CUREE (Consortium of Universities for Earthquake Engineering) general displacement-based protocol.
Variables investigated within the main study were the following: the use of OSB versus plywood sheathing, the effect of priming and surface sanding on adhesion, and the comparison of connections involving mechanical fasteners with those that utilized only adhesive tape or a combination of the two. It was found that an application pressure of 207 kPa (30 psi) or greater was needed to form a sound bond between the acrylic foam adhesive tape and a wood substrate. Properly bonded OSB and plywood connections provided fairly ductile failure modes. Full-scale walls constructed with adhesive tape performed similarly to traditional wall configurations, while walls constructed with a combination of adhesive tape and mechanical fasteners provided significant gains in strength and toughness. The results of this study serve to provide a foundation for expanding the engineering uses of acrylic foam adhesive tape for structural applications.
Master of Science
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El, Hage Roland. "Prétraitement du miscanthus x giganteus : vers une valorisation optimale de la biomasse lignocellulosique." Thesis, Nancy 1, 2010. http://www.theses.fr/2010NAN10063/document.
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Le miscanthus x Giganteus (MxG) constitue, du fait de sa composition, une source renouvelable de matière lignocellulosique pouvant être d'un grand intérêt pour la production de molécules à haute valeur ajoutée. Le MxG ayant servi à ce travail provient du lycée agricole à Courcelles-Chaussy, Metz-France. Sa teneur élevée en hémicelluloses (26 %), en lignine (26 %) et en cellulose (36 %) en fait une bonne source de polymères et de carburant renouvelable. L'étude que nous avons réalisée a été menée dans le but de caractériser la paille de MxG et d'optimiser le processus de délignification en une seule étape (1) par un traitement organosolv à l'éthanol et en deux étapes (2) par un prétraitement consistant en une autohydrolyse à l'eau/organosolv. Le procédé éthanol organosolv a permis un bon fractionnement des trois constituants de la biomasse (la lignine, la cellulose et les hémicelluloses). Le procédé de traitement en deux étapes, impliquant une autohydrolyse à l'eau (en présence et en l'absence du 2-naphtol), préalable au traitement organosolv, a permis de faciliter l'étape ultérieure de délignification en déstructurant la lignine. Une investigation portant sur la structure physico-chimique a été réalisée sur de la lignine de bois broyé et de la lignine organosolv de MxG extraite à différentes sévérités de traitement. Nous nous sommes ensuite intéressés à utiliser la lignine organosolv pour la formulation d'un adhésif pour le bois dans laquelle un aldéhyde non toxique et peu volatile (le glyoxal) est employé en remplacement du formaldéhyde. Une formulation, composée à 100 % de résines naturelles (60 % de tannins de mimosa et 40 % de lignine glyoxalée) a été utilisée pour la conception d'un panneau de particules et a donné des résultats prometteurs avec une force de liaison interne de 0,41 MPa, supérieure à la valeur de la norme européenne en vigueur. Enfin, une étude des propriétés antioxydantes a été faite sur les lignines extraites. Les résultats obtenus ont montré une corrélation entre l'activité antioxydante et les conditions opératoires du traitement organosolv, la masse moléculaire moyenne, l'indice de polydispersité et les groupements hydroxyles phénoliques des ligninesMiscanthus x giganteus (MxG) is, because of its composition, a source of renewable lignocellulosic material that can be of great interest for the production of high added value molecules. MxG used in this work comes from the agricultural high school of Courcelles-Chaussy, Metz-France. Its high content of hemicelluloses (26 %), lignin (26 %) and cellulose (36 %) makes it a good source of polymers and renewable fuel. In the present study we have characterized the straw of MxG and optimized the process of delignification in a single step (1) by an ethanol organosolv treatment and in a two steps (2) including an autohydrolysis pretreatment with water / organosolv. The ethanol organosolv process permits a good separation of the three constituents of our biomass (lignin, cellulose and hemicelluloses). The two steps treatment process, involving an autohydrolysis with water (in the presence or absence of 2-naphthol) before the pretreatment organosolv has facilitated the later stage of delignification in destructurizing the lignin. An investigation of the physico-chemical properties was performed on the structure of the milled wood lignin and organosolv lignin of MxG extracted with different treatment severities. A way of valorization for the organosolv lignin has been proposed by their incorporation in the formulation of an adhesive for wood in which a non volatile and low toxic aldehyde (glyoxal) is used instead of formaldehyde. A formulation consisting in 100 % of natural resins (60 % tannins of mimosa and 40 % of glyoxalated lignin) was used for the production of particle board and gave promising results with internal bond strength of 0.41 MPa, higher than the value of the current European standard. Finally, a study was conducted on the antioxidant properties of organosolv lignin extracted at different severities. The results have shown a correlation between the antioxidant activity and the operating conditions of treatment organosolv, the average molecular weight, the polydispersity index and the phenolic hydroxyl groups of lignin
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Nicoli, Edoardo. "Characterization of Mixed-Mode Fracture Testing of Adhesively Bonded Wood Specimens." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/28372.
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The primary focus of this thesis was to investigate the critical strain energy release rates (G) for mixed-mode (I/II) fracture of wood adhesive joints. The aims of the study were: (1) quantifying the fracture properties of two material systems, (2) analyzing the aspects that influence the fracture properties of bonded wood, (3) refining test procedures that particularly address layered orthotropic systems in which the layers are not parallel to the laminate faces, of which wood is often a particular case, and (4) developing testing methods that enhance the usefulness of performing mixed-mode tests with a dual-actuator load frame. The material systems evaluated experimentally involved yellow-poplar (Liriodendron tulipifera), a hardwood of the Magnoliaceae family, as adherends and two different adhesives: a moisture-cure polyurethane (PU) and a phenol/resorcinol/-formaldehyde (PRF) resin. The geometry tested in the study was the double cantilever beam that, in a dual-actuator load frame, can be used for testing different levels of mode-mixity. The mixed-mode loading condition is obtained by applying different displacement rates with the two independently controlled actuators of the testing machine.
Characteristic aspects such as the large variability of the adhesive layer thickness and the intrinsic nature of many wood species, where latewood layers are alternated with earlywood layers, often combine to confound the measures of the critical values of strain energy release rate, Gc. Adhesive layer thickness variations were observed to be substantial also in specimens prepared with power-planed wood boards and affect the value of Gc of the specimens. The grain orientation of latewood and earlywood, materials that often have different densities and elastic moduli, limits the accuracy of traditional standard methods for the evaluation of Gc. The traditional methods, described in the standards ASTM D3433-99 and BS 7991:2001, were originally developed for uniform and isotropic materials but are widely used by researchers also for bonded wood, where they tend to confound stiffness variations with Gc variations. Experimental analysis and analytical computations were developed for quantifying the spread of Gc data that is expected to be caused by variability of the adhesive layer thickness and by the variability of the bending stiffness along wooden beams.Ph. D.
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Manaâ, Rabah. "Étude de la ténacité des assemblages bois-colle résorcine-phénol-formol." Vandoeuvre-les-Nancy, INPL, 1995. http://www.theses.fr/1995INPL028N.
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La méthode de détermination de l'énergie de rupture GIC d'une éprouvette DCB (Double Cantilever Beam) en bois collée à la résorcine-phénol-formol, considère un bras de l'éprouvette comme une poutre élastique sur fondations viscoélastiques dont les constantes de la loi de comportement sont déterminées en réalisant des essais au viscoanalyseur. La méthode de la complaisance expérimentale établie par Sassaki a été adoptée pour déterminer l'énergie de rupture GIC. La solution du problème est d'assimiler le matériau de l'éprouvette DCB à un modèle de Zener ou le bois est considéré comme un matériau élastique et représente par un ressort, alors que la colle est considérée comme un matériau viscoélastique et représente par un modèle de Voigt (un ressort et un amortisseur en parallèle). L’énergie de rupture du modèle est déterminée par la relation (P-d). Les résultats sont satisfaisants dans la mesure où la différence des énergies entre les valeurs expérimentales et celles du modèle est très minime
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Scott, Keith Alan. "Economic Feasibility of Implementing a Resin Distribution Measurement System for MDF Fiber." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/31835.
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There have been successful techniques developed to measure resin distribution of phenol-formaldehyde adhesive on several types of wood surfaces. However, a technique that quantitatively measures UF resin on wood surfaces has been a problem because UF resin is colorless on wood fiber. The first objective of this study was to develop a technique to quantitatively measure surface area coverage and statistical distribution of urea-formaldehyde (UF) resin on medium density fiberboard (MDF) fiber. Two techniques were evaluated to quantitatively measure UF resin. One technique treated the resinated fiber with a reactive stain, such that the resin and wood could be distinguished and separated using digital image analysis. An epi-fluorescence microscope, color video camera, A/D image capture board, and image analysis software were used to measure the percent of resin coverage on the wood surface. The measured resin coverage of the treated fibers did not correlate with the target resin loading level. The other technique added ultraviolet dye to the resin and measured the distribution of resin with an image analysis system. The results of a mill trial confirmed the accuracy of the technique. This system has potential to be incorporated into a mill setting, which will provide MDF mills with a method of determining how resin is being distributed on their fiber.
The second objective of this study was to identify factors that would influence the technique's acceptance among MDF mills. A questionnaire was developed, pretested, and sent to every MDF mill in the United States. The method of adding UV dye into the resin was favorable to most mills and could be tested either on-site or by a third-party company. This allows MDF mills to determine potential problems with their blending process. This method saves time and money since it is a proactive measure rather than a reactive measure. It should also lead to a more uniform and consistent product, which is the goal of every MDF mill.Master of Science
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Liu, Haijing. "Wet adhesion properties of oilseed proteins stimulated by chemical and physical interactions and bonding." Diss., Kansas State University, 2017. http://hdl.handle.net/2097/35774.
Full textAbstract:
Doctor of PhilosophyDepartment of Grain Science and Industry
X. Susan Sun
The ecological and public health liabilities related with consuming petroleum resources have inspired the development of sustainable and environmental friendly materials. Plant protein, as a byproduct of oil extraction, has been identified as an economical biomaterial source and has previously demonstrated excellent potential for commercial use. Due to the intrinsic structure, protein-based materials are vulnerable to water and present relatively low wet mechanical properties. The purpose of this study focuses on increasing protein surface hydrophobicity through chemical modifications in order to improve wet mechanical strength. However, most of the water sensitive groups (WSG), such as amine, carboxyl, and hydroxyl groups, are also attributed to adhesion. Therefore, the goal of this research is to reduce water sensitive groups to an optimum level that the modified soy protein presents good wet adhesion and wet mechanical strength. In this research, we proposed two major approaches to reduce WSG: 1). By grafting hydrophobic chemicals onto the WSGs on protein surface; 2). By interacting hydrophobic chemicals with the WSGs. For grafting, undecylenic acid (UA), a castor oil derivative with 11-carbon chain with a carboxyl group at one end and naturally hydrophobic, was used. Carboxyl groups from UA reacted with amine groups from protein and converted amines into ester with hydrophobic chains grafting on protein surface. The successful grafting of UA onto soy protein isolate (SPI) was proved by both Infrared spectroscopy (IR) and ninhydrin test. Wood adhesive made from UA modified soy protein had reached the highest wet strength of 3.30 ± 0.24 MPa with fiber pulled out, which was 65% improvement than control soy protein. Grafting fatty acid chain was verified to improve soy protein water resistance. For interaction approach, soy oil with three fatty acid chains was used to modify soy protein. Soy oil was first modified into waterborne polyurethanes (WPU) to improve its compatibility and reactivity with aqueous protein. The main forces between WPU and protein were hydrogen bonding, hydrophobic interactions, and physical entanglement. Our results showed that WPU not only increased protein surface hydrophobicity with its fatty acid chains but also enhanced the three-dimensional network structure in WPU-SPI adhesives. WPU modification had increased wet adhesion strength up to 3.81 ± 0.34 MPa with fiber pulled out compared with 2.01 ± 0.46 MPa of SPI. Based on IR and thermal behavior changes observed by DSC, it was inferred that a new crosslinking network formed between WPU and SPI. To exam if the UA and WPU technologies developed using soy protein are suitable for other plant proteins, we selected camelina protein because camelina oil has superior functional properties for jet fuels and polymers. Like soy protein, camelina protein is also highly water sensitive. However, simply applied UA and WPU to camelina protein following the same methods used for soy proteins, we did not obtain the same good adhesion results compared to what we achieved with soy protein. After protein structure analysis, we realized that camelina protein is more compact in structure compared to soy protein that made it weak in both dry and wet adhesion strength. Therefore, for camelina protein, we unfolded its compact structure with Polymericamine epichlorohydrine (PAE) first to improve flexible chains with more adhesion groups for future reaction with UA or WPU. PAE with charged groups interacted camelina protein through electrostatic interaction and promoted protein unfolding to increase reactivity within protein subunits and between protein and wood cells. Therefore, the wet adhesion strength of camelina protein was improved from zero to 1.30 ± 0.23 MPa, which met the industrial standard for plywood adhesives in terms of adhesion strength. Then the wet adhesion strength of camelina protein was further improved after applying UA and WPU into the PAE modified camelina protein. In addition, we also found PAE unfolding significantly improved the dry adhesion strength of camelina protein from 2.39 ± 0.52 to 5.39 ± 0.50 MPa with 100% wood failure on two-layer wood test. Camelina meal which is even more economical than camelina protein was studied as wood adhesive. Through a combination of PAE and laccase modification method, the wet adhesion strength of camelina meal was improved as high as 1.04 ± 0.19MPa, which also met industrial standards for plywood adhesives. The results of this study had proven successful modification of oilseed protein to increase water resistance and wet mechanical strength. We have gained in-depth understanding of the relationship between protein structure and wet adhesion strength. The successful modification of plant proteins meeting the industrial needs for bio-adhesives will promote the development of eco-friendly and sustainable materials.
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Scoville, Christopher R. "Characterizing the Durability of PF and pMDI Adhesive Wood Composites Through Fracture Testing." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/35353.
Full textAbstract:
The increased use of wood composites in building materials results in a need for a better understanding of wood adhesion. The effects of water and temperature exposure on the durability of wood products were assessed using the double-cantilever beam (DCB) method of fracture testing. The relative durability of phenol-formaldehyde (PF) and isocyanate (pMDI) adhesives was compared using a 2-hour boil test and an environmental test. The feasibility of using oriented strandboard (OSB), oriented strand lumber (OSL) and parallel strand lumber (PSL) for the DCB fracture method was assessed. The fracture resistance of PF was reduced significantly by the aging exposures. The fracture resistance of pMDI did not decrease after the 2-hour boil test. The DCB fracture method was shown to be useful with a square-grooved machined specimen using OSB and OSL.Master of Science
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He, Wenchang. "Effects of adhesive z-connections on the properties of a model wood composite." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/61308.
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Adhesive is a costly and critical component of wood composites. The relationship between adhesive distribution and properties of wood composites has been explored, but few studies have attempted to alter the distribution of adhesive in wood composites as a way of improving their properties. In this thesis, I hypothesize that creating a 3-dimensionally inter-connected adhesive network by introducing adhesive Z-connections will improve two key properties of wood composites (thickness swelling and fracture toughness). Both experiments and computer simulation (finite element analysis) were carried out to test this hypothesis. I developed a methodology to precisely perforate veneer to facilitate the creation of adhesive Z-connections when the composite was pressed. Adhesive Z-connections are defined as the cured adhesive distributed in the Z- (thickness) direction (in addition to the X-Y directions) of the laminated wood composite due to the perforation in veneer. I examined factors affecting the ability of Z-connections to improve dimensional stability and fracture toughness of a model wood composite. I visualized the adhesive distribution in the composite in 2D and 3D using macro-photography, X-ray micro-computed tomography and scanning electron microscopy. Significant improvements in dimensional stability and fracture toughness of some of the composites were observed. Key parameters affecting the ability of adhesive Z-connections to reduce thickness swelling were diameter and spatial arrangement of Z-connections, adhesive level and wood species used to make the composite. Key parameters affecting the ability of adhesive to increase the fracture toughness of a model wood composite were area-density of Z-connections and reinforcement of the adhesive in the composite. I conclude that introducing adhesive Z-connections can reduce thickness swelling and enhance fracture toughness of wood composites, but the effectiveness of such an approach is affected by wood species, area-density and spatial arrangement of the Z-connections. I discuss the implications of my findings for the development of wood composites with enhanced dimensional stability and fracture toughness and further research needed to capitalize on the concept of creating an inter-connected 3D adhesive network in wood composites by introducing adhesive Z-connections.Forestry, Faculty of
Graduate
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Gagliano, Jerone Matthew. "An Improved Method for the Fracture Cleavage Testing of Adhesively-Bonded Wood." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/31510.
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This work describes the development of an improved mode I fracture testing procedure for adhesively-bonded wood, and demonstrates the sensitivity of this approach. The two significant improvements were: 1) the use of the flat double cantilever beam (DCB) geometry, which has been uncommon for wood and 2) the application of an established and powerful data analysis using a corrected compliance method from beam theory. Three studies were conducted using various wood adhesives and DCB specimens were fabricated from yellowpoplar (Liriodendron tulipifera) sapwood.
The sensitivity of this methodology showed significant differences in fracture performance as the degree of cure increased for a phenol formaldehyde adhesive, and yielded maximum strain energy release rate (SERR) values of 370 - 560 J/m2. A second study showed performance differences between two polymeric diphenylmethane diisocyanate (pMDI) adhesives and one polyurethane adhesive. Typical maximum SERR values were 160 and 130 J/m2 for the pMDI adhesives and 160 J/m2 for the polyurethane adhesive. A third study investigated the effect of loading rates on a cross-linked polyvinyl acetate adhesive and maximum SERR values of 370 - 560 J/m2 were achieved.
Adhesive penetration and cure were determined by image analysis with fluorescence microscopy, and by micro-dielectric analysis, respectively. Since the geometry of the fracture procedure dictates the absence of wood failure, the resulting fractured surfaces were readily analyzable. The surface analysis techniques of laser ionization mass analysis, solid-state nuclear magnetic resonance and field emission scanning electron microscopy were used to investigate the locus of failure for the smooth fractured surfaces.Master of Science
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Li, Yuqin. "Factors Affecting the Structural Integrity of Wood-Based Composites: Elevated Temperature and Adhesive Bonding." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/102927.
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This study focuses on factors that affect the structural integrity of wood-based composites. Wood-based composites exposed to fire may decompose due to the elevated temperatures, resulting in a degradation in performance. Thermal modelling can only predict the structural integrity of construction materials in fire if it is given accurate inputs. Consequently, methods for the characterization of the thermal, physical, and mechanical behaviors of wood and wood-based composites are selected, designed, and benchmarked. The relevant thermal and physical responses characterized includes porosity, permeability and thermal diffusivity. Common construction materials (white pine board, medium density fiberboard and spruce 24) are characterized from room temperature to complete decomposition. The characterization techniques and processes are based on existing literature and relevant ASTM standards. To reduce the number of experiments required for future material characterization, estimates based upon the degree of decomposition and the measured values for the virgin and charred materials are used. For porosity and thermal diffusivity, these models allow values at intermediate temperatures to be estimated with measurements at room temperature and complete decomposition and thermogravimetric analysis (TGA). We find that permeability depends heavily on the microstructure of materials and should be measured independently at the conditions of interest.
An additional important aspect of the performance of wood-based composites is the fracture behavior of wood/adhesive systems. Adhesive bonding enables many engineered wood products such as furniture and structural wood joints and the adhesive fracture toughness often determines the durability. The conventional characterization method for wood/adhesive fracture resistance relies on samples with machined grain angles designed to funnel cracks to the adhesive interface. This method of sample preparation is difficult and time-consuming for certain wood species. In this work, a practical and efficient method is developed to characterize adhesive fracture energy of adhesively bonded veneer systems. In the method, auxiliary aluminum adherends are bonded to the veneers in an effort to drive the crack to the wood/adhesive interface. The method is applied to rotary-peeled veneers and saw-cut veneers produced from three species of wood bonded with three commonly used adhesives. The new tests method yields a high interfacial failure rate and successfully identifies differences in the performance of the three adhesives. SPG (one species of the rotary-peeled veneers) demonstrates a rising R-curve behavior (an increase in the fracture toughness with crack length) when bonded on the loose side. This increase in fracture toughness is observed to be a result of adhesive-substrate interaction, which is a developing process zone behind the crack tip consisting of bridged wood ligaments.Doctor of Philosophy
Construction materials exposed to elevated temperatures from fires may reach temperatures where the material decomposes from the original material to a char. Protected and unprotected structural timber products exposed to fires may exhibit this behavior resulting in a degradation of performance. Understanding the thermal and physical responses of these materials is crucial in evaluating the materials behavior in fire. Additionally, many wood-based products (such as furniture) rely on adhesive bonds. Consequently, their usefulness is determined by the performance of those bonds. In this work, methods are developed to measure key properties impacting the behavior of wood-based systems at elevated temperatures, such as that experienced in fires and when they are subjected to forces attempting to debond one wood material from another. These techniques are demonstrated on common building materials (white pine board, medium density fiberboard and spruce 24) and wood veneers from three different species bonded with three different adhesives. Mathematical models are developed to expand the use of the data beyond the specific conditions for which it is measured.
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Torneport, Matilda. "Industrial Requirements for Cross-Laminated Timber Manufacturing." Thesis, Linnéuniversitetet, Institutionen för skog och träteknik (SOT), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-104924.
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Wood is a valuable sustainable material that meets the requirements for structural application. Cross-laminated timber (CLT) is a wood-based product that is mainly used in the building industry. Due to the rapid global market increase, a number of new CLT plants are emerging worldwide and thereby a need for standardisation is more than ever. There is no existing harmonised standard for CLT and it means a diversity between manufacturers, CLT products and its layup, which may in turn affects the properties of available CLT in the market. Therefore, this study was performed through literature study and internet-based interviews from five manufacturer in Sweden and Central Europe, to provide more information regarding the industrial requirements for CLT production. Three specific objectives of this study were: (1) wood and adhesive types in CLT production, (2) wood strength classes for CLT production, (3) important requirements for CLT producers and existing standards. Literature review and interviews showed that spruce (Picea abies L. Karst.) in combination with polyurethane (PUR) adhesive is the most commonly used materials in Europe for CLT production, which are approved by EN 16351 (2021). Other wood species, e.g., pine, poplar and birch can be used or are already used in a minor extent. Strength classes for lamellas in CLT are often C24, but timbers with lower strength grades are possible. Some manufacturer use combinations of different strength graded timber and in this small scale study different strength graded timber was in generally the biggest diversity between manufactures. Only a few material properties such as modulus of elasticity, modulus of rupture, compression and shear strength are listed in EN 16351 (2021) and EN 338 (2016), as the factors for quality measurements of the CLT products. This study, however, showed that the critical material properties for the most interviewed CLT producers are merely modulus of elasticity and rarely modulus of rupture.
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Eisenheld, Leopold. "Measuring the Adhesive Bond Quality of Vinyl Ester-Glass Composites on Novolak HMR Treated Wood." Fogler Library, University of Maine, 2003. http://www.library.umaine.edu/theses/pdf/EisenheldL2003.pdf.
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Peng, Yucheng. "EFFECT OF HIGH TEMPERATURES ON ADHESIVE BOND DURABILITY AND TOXIC CHEMICAL PRODUCTION FOR ENGINEERED WOOD PRODUCTS." MSSTATE, 2008. http://sun.library.msstate.edu/ETD-db/theses/available/etd-07082008-153319/.
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The objectives of this research were to investigate the heat resistant performance of a structural adhesive and to analyze the contribution of the adhesive to the chemical emissions from the glued wood products affected by the elevated temperatures. Phenol-resorcinol-formaldehyde (PRF) and two wood species, southern pine (Pinus palustris) and Douglas-fir (Pseudotsuga menziesii), were investigated. The dynamic mechanical analysis (DMA) test results showed that the heat durability performance of cured PRF resin was better than that of the two wood species used in this study. The results indicated that the fire safety of PRF bonded wood products should be comparable to solid wood products. The pyroysis products obtained from pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) system showed that most of the pyrolysis products of glued wood samples were same as those of wood and adhesive samples at the same temperature level except a few compounds, such as carbon disulfide, Cyclopropyl carbinol, acetaldehyde, furfural and others.
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Liswell, Brian P. "Exploration of Wood DCB Specimens Using Southern Yellow Pine for Monotonic and Cyclic Loading." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/9955.
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The primary direction of this thesis was towards exploring qualitative and quantitative characteristics necessary for refining and understanding the flat wood double cantilever beam (DCB) as a valid means for testing Mode I fracture energy in wood adhesive bonds. Southern yellow pine (SYP) adherends were used with epoxy and phenol formaldehyde (PF) impregnated films, providing two systems with different characteristics for investigation.
An adhesive penetration analysis was performed for both the epoxy and PF bonds. The PF penetration into the SYP was shown to be relatively shallow. The epoxy penetration was shown to be deeper. Epoxy-SYP DCBs were quasi-statically tested with varying widths (10 mm, 15 mm, and 20 mm), showing decreases in scatter of critical and arrest strain energy release rates, GIc and GIa, with increases in specimen width. Quasi-static fracture testing was also performed on PF SYP-DCBs, showing much higher critical and arrest fracture energy values than the epoxy-SYP DCBs, indicating that deep adhesive penetration is not necessarily a requisite for higher Mode I fracture energy values.
Grain distribution influences were computationally investigated because of the stiffness difference between latewood and earlywood growth and the grain angle along the length of the beams. The grain angle and the stiffness difference between latewood and earlywood growth caused the effective stiffness, (ExxI)eff, to vary along the length of the beam. The effective stiffness variation caused variations in the beam's ability to receive and store strain energy, complicating and confounding determination of experimental results.
Cyclic loading tests were performed on PF-SYP DCB's. The cycle frequency was 3Hz, with a valley to peak load ratio of R = 0.5. Specimen softening was observed with cycling, with re-stiffening occurring with crack growth. Contrary to expectations, specimen compliance occasionally decreased with small crack extensions. A toughening mechanism was frequently observed, whereby subsequent crack lengths required more cycles to failure than the previous crack length. Monotonically extending the crack length far from the fatigued region created a fresh crack that did not show the toughened behavior. But toughening did resume with subsequent crack lengths.Master of Science