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1
Lowe, David James. "Natural rubber/organoclay nanocomposites." Thesis, Queen Mary, University of London, 2012. http://qmro.qmul.ac.uk/xmlui/handle/123456789/2971.
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Natural rubber (NR)/organoclay nanocomposites were prepared using organomontmorillonite (OMMT) and organo-sepiolite (OSEP). Both were found to improve modulus significantly more than equivalent amounts of conventional fillers such as carbon black for strains up to 100%. OSEP was found to increase modulus more than OMMT for a given filler content, and NR/OSEP nanocomposites also had potentially anisotropic physical properties. OMMT had more effect on vulcanisation than OSEP, although both produced considerable acceleration. The tensile stress-strain behaviour of NR/OMMT and NR/OSEP nanocomposites were studied using a number of different micromechanical models. Some models were found to give a good empirical fit with experimental data, with the best results given by the Halpin-Tsai model. Furthermore, by analysis of the vulcanisation behaviour using rheometry, and particle morphology using transmission electron microscopy (TEM), it was possible to accurately estimate the Young's modulus of a nanocomposite from knowledge of the cure onset time and the shape factor of the particles. It was discovered that unmodified montmorillonite and sepiolite clays could undergo organic modi cation in situ during mixing into NR following the addition of a suitable modifier. This resulted in vulcanisates with very similar physical properties to those found when using pre-modified OMMT or OSEP. TEM and X-ray diffraction showed that the exfoliation state of the clay modified in situ was also similar to that of pre-modified organoclay. Silane coupling agents were also used with NR/OMMT and NR/OSEP nanocomposites, producing significant increases in modulus. However, the increased modulus was only observed above 40% strain for OMMT and above 25% for OSEP. The coupling agents strengthens the rubber- ller interface preventing interfacial slippage and cavitation in the nanocomposite, and these mechanisms only begin to operate when the interfacial stress reaches a significant level. The most effective coupling agent used was bis[triethoxysilylpropyl] tetrasulfide due to its relatively high reactivity.
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Lewan, Michael Victor. "Crosslink density distributions in natural rubber/nitrile rubber blends." Thesis, Loughborough University, 1995. https://dspace.lboro.ac.uk/2134/32972.
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An NMR technique has recently been developed to determine the crosslink density in each phase of a polymer blend. This work uses the NMR method to study natural rubber (NR)/acrylonitrile butadiene rubber (NBR) blends, in order that the cure system used to vulcanize such blends can be optimized. A standard injection moulding cure system for NR/Perbunan N1807 (18% acrylonitrile content) gave much more crosslinking in the NBR phase. To reduce this imbalance a less polar analogue of the accelerator was used, resulting in a more even distribution of crosslinks but still with a bias towards the NBR.
3
Intharapat, Punyanich. "Thermoplastic natural rubbers based on natural rubber (NR) and ethylene vinyl acetate copolymer (EVA) with natural rubber-graft- poly(dimethyl(methacryloyloxymethyl)phosphonate) (NR-g-PDMMMP) as compatibilizer." Le Mans, 2009. http://cyberdoc.univ-lemans.fr/theses/2009/2009LEMA1005.pdf.
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Des copolymères greffés à base de caoutchouc naturel (NR) et de poly(acryloyloxyméthylphosphonate de diméthyle) (NR-g-PDMAMP), de poly(méthacryloyloxyéthylphosphonate de diméthyle) (NR-g-PDMMEP) et de poly(méthacryloyloxyméthylphosphonate de diméthyle) (NR-gPDMMMP), ont été synthétisés en milieu latex selon la méthode dite « grafting from » à partir de sites amorceurs photosensibles N ,Ndiéthyldithiocarbamate préalablement introduits le long des chaînes 1,4-polyisoprène du caoutchouc naturel. Des études de compatibilisation des mélanges caoutchouc naturel (NR) / copolymère d'éthylène - acétate de vinyle (EV A) ont par la suite été envisagées avec le copolymère NR-gPDMMMP, choisi comme agent compatibilisant. Elles ont été effectuées sur des mélanges simples 50/50 NR/EV A, mais aussi des mélanges dynamiquement vulcanisés 40/60 NR/EVA. Dans les deux cas,les influences du taux de greffage du NR-g-PDMMMP (71, 80, 89, et 95%) et du taux de chargement en compatibilisant (0, 1,3,5,7,9,12, et 15 % en poids par rapport au NR) sur les propriétés rhéologiques, dynamiques, mécaniques, morphologiques, et thermiques, ont été étudiées. Les meilleurs effets de compatibilisation ont été observées avec un copolymère NR-g-PDMMMP ayant un taux de greffage de 80 %, pour un taux de chargement de 7 % dans le cas du mélange simple 50/50 NR/EV A et de 9 % dans celui du mélange dynamiquement vulcanisé 40/60 NR/EV A. Les études microscopiques par SEM des mélanges ont montré une réduction de la taille des domaines. Il a aussi été noté que la stabilité thermique du mélange NR/EVA se trouve renforcée avec l'incorporation du NR-g-PDMMMPGraft copolymers of natural rubber and poly(dimethyl(acryloyloxymethyl)phosphonate) (NR-g-PDMAMP), natural rubber and poly(dimethyl(methacryloyloxyethyl)phosphonate) (NR-g-PDMMEP), and natural rubber and poly(dimethyl(methacryloyloxymethyl)phosphonate) (NR-g-PDMMMP), were prepared in latex medium via a "grafting from" methodology based on the photopolymerization of vinyl monomers initiated from N,N-diethyldithiocarbamate groups previously bound in side position of the 1,4-polyisoprene chains of natural rubber. Thereafter, compatibilization studies of natural rubber (NR) / ethylene vinyl acetate copolymer (EV A) blends were considered using NR-g-PDMMMP as a blend compatibilizer. The investigations were carried out on two categories of blends : uncured 50/50 and dynamically cured 40/60 NR/EV A blends. Ln the two cases, the influences of NR-g-PDMMMP grafting rates (i. E. , 71, 80, 89, and 95 %) and of loading level in compatibilizer (i. E. , 0, 1,3,5,7,9,12, and 15 wt% compared to NR) on rheological, dynamical, mechanical, morphological, and thermal properties, were studied. The best compatibilization effects were observed with a NR-g-PDMMMP having a grafting rate equal to 80 %, at a loading level of 7 wt% for 50/50 uncured blend and 9 wt% for 40/60 dynamically cured blend. In these conditions, the highest complex viscosity (positive deviation), tensile strength, and elongation at break, as well as the lowest values of tension set and tan d (damping factor), were observed. SEM micrographs of compatibilized blends showed a size decrease of the domains. It was also noted that the thermal stability of NR/EV A blends was improved by incorporating NR-g-PDMMMP
4
Chumeka, Wannapa. "Improvement of compatibility of poly(lactic acid) blended with natural rubber by modified natural rubber." Phd thesis, Université du Maine, 2013. http://tel.archives-ouvertes.fr/tel-01018026.
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The aim of this research work was to improve the compatibility of polymer blends made from poly(lactic acid) and natural rubber (PLA/NR blends) by using modified natural rubber as a compatibilizer. Natural rubber was chemically modified into two categories: natural rubber grafted poly(vinyl acetate) copolymer (NR-g-PVAc) and block copolymers (PLA-NR diblock copolymer and PLA-NR-PLA triblock copolymer). PLA/NR blends were prepared by melting blending in a twin screw extruder and compression molded to obtain a 2-mm thick sheet. The blends contained 10-20 wt% of NR and modified NR, and the impact strength and tensile properties were investigated. The compatibilization effect was determined by DMTA, DSC and SEM. NR-g-PVAc was synthesized by emulsion polymerization to obtain different PVAc graft contents (1%, 5% and 12%). Characterization by DMTA showed an enhancement in miscibility of the PLA/NR-g-PVAc blends. NR-g-PVAc could be used as a toughening agent of PLA and as a compatibilizer of the PLA/NR blend. The block copolymers were synthesized following two routes: (1) hydroxyl telechelic natural rubber (HTNR) and lactide and (2) HTNR and PLA prepolymer. In the former route, lactide was in situ polymerized via a ring opening polymerization to be a PLA block segment during block copolymerization. In the latter route PLA prepolymer was synthesized by a condensation polymerization of L-lactic acid prior to block copolymerization. Both block copolymers acted as good compatibilizers for the PLA/NR blend by increasing the impact strength and decreasing the NR particle size. Triblock copolymers provided higher impact strength than diblock copolymers, and they were a less effective compatibilizer than NR-g-PVAc. In contrast to NR and NR-g-PVAc, the block copolymer was not a good toughening agent for PLA.
5
Said, M. M. "Peroxide prevulcanization of natural rubber latex." Thesis, London Metropolitan University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233004.
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The peroxide prevulcanization of NR latex using a range of commercially-available organic peroxides and an inorganic peroxide (potassium peroxydisulphate), in both activated and non-activated systems, has been investigated. A range of reducing agents and compounds that are known to promote peroxide-initiated emulsion polymerization and peroxide curing of po1yesters have been evaluated as promoters for the peroxide prevulcanization of NR latex. A few reactive peroxyesters have been found to be effective as prevulcanizing agents at temperatures in the range 80 °C-lOO °C. the effectiveness of the prevulcanization systems was characterized by the rate and efficiency of crosslinking achieved by these systems. Fructose-activated peroxyester and fructoseactivated hydroperoxide systems were found to effect prevulcanization at temperatures in the range 50 °C-80 °C. There is no clear correlation between the structure/reactivity of peroxyesters and the effectiveness of fructose-activated prevulcanization systems. The relative reactivity of the alkoxy radicals generated by the commercial hydro peroxides PQ~tly exp\a~~s the differences in the effectiveness of various fructose-activated hydroperoxide prevulcanization systems. The prevulcanization kinetics for the fructose-activated t-butyl peroxyisobutyrate (tBPIB) system have been investigated. The overal rate of tBPIB decomposition in NR latex, in both non-activated and fructose-activated systems was found to be first-order reaction with respect to tBPIB concentration. However, investigation of initial rate of tBPIB decomposition in NR latex indicates that the initial rate of tBPIB decomposition in NR latex is half order with respect to initial tBPIB concentration. This is probably a consequence of induced decomposition of tBPIB by certain non-rubber substances, and_termination by recombination of radicals derived from tBPIB. But, the reason for the difference in the reaction order with respect to tBPIB concentration, at the initial stage of the reaction and during the run is not clear. The prevulcanization kinetics also exhibit a number of other peculiar characteristics. Thus at temperatures greater than 70°C, and using a high fructose concentration, the rate coefficient for crosslink formation tends to be greater than that for peroxide decomposition. This is probably attributed to the differences in the temperature-coefficients of the various competing reactions during peroxide prevulcanization of NR latex. The instantaneous crosslinking efficiency was found to increase linearly with prevulcanization time. At temperatures greater than 70°C, the instantaneous crosslinking efficiency can attain values greater than 50%, indicating the involvement of alkyl radicals as well as the alkoxy radicals in the crosslinking reaction. The experimental activation energies for peroxide decomposition and crosslink formation were found to decrease to apparently constant values with increasing fructose/ peroxide concentration ratio. The rate of tBPIB decomposition was found to be significantly determined by activation free energy and not just activation energy for the decomposition. The factors which influence the physical properties of films from peroxide-prevulcanized NR latex have been investigated. The crosslink concentration was found to be the most important factor in determining the physical properties of films from peroxide-prevulcanized NR latex. Factors that account for the differences in the physical properties of films from peroxide- and sulphur-prevulcanized latices, and peroxide gum NR vulcanizates have been discussed. Attempts to improve the ageing properties of films from peroxideprevulcanized NR latex indicate that a preventive antioxidant is an essential component for an effective antioxidant system for these films.
6
Bhala, Maclean J. "Non-migratory antiozonant system for natural rubber." Thesis, Loughborough University, 1997. https://dspace.lboro.ac.uk/2134/12428.
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The current research on non-migratory antiozonant systems for natural rubber follows a tripartite study involving the formulation of a coating compound with static and dynamic ozone testing of the coatings, a review of some commercial in-mould coating techniques and analysis of diffusion of a commercial antiozonant through a coating. An outline of the mixing of Nipol 1312, a low molecular weight nitrile butadiene rubber grade produced by leon Chemicals Inc., with other ingredients to produce a coating composition is also given. Test pieces of the natural rubber substrate were placed in pre-coated mould cavities and cured under compression to achieve covulcanisation between the substrate and the coating. All ozone tests were carried out under standard ASTM DI149-911D518-91 conditions. Results show that the formulated nitrile rubber coating compound is able to protect natural rubber from ozone attack with no migration of the antiozonant as in classical chemical antiozonant systems. An up to date patent search on in-mould coating techniques and systems was carried out and evaluated in conjunction with some current commercial coating methods. In this overview, more emphasis is laid on the nature of the coating material which subsequently determines the appropriate coating technique, than on the specific in-mould coating process applied. Post-mould coating work with polyvinyl chloride (PVC) on natural rubber substrate was also assessed. An experimental and theoretical study of the diffusion of the antiozonant N,Isopropyl N-phenyl-pphenylenediamine (IPPD) through a protective coating on a natural rubber substrate is made in the project. This study shows that the protective coating is able to reduce the loss of antiozonant through diffusion while giving the rubber adequate protection from ozone. The study also demonstrates that the combination of a commercial antiozonant and a protective coating gives enhanced product service life and provides protection to damaged regions of the coating.
7
South, Joseph Thomas. "Mechanical Properties and Durability of Natural Rubber Compounds and Composites." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/26306.
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The focus of this research was to investigate the effect of thermal degradation upon the mechanical properties of natural rubber compounds and apply those effects to the life prediction of off axis 2-ply cord rubber laminates. The work examined both the quasi-static and dynamic mechanical properties of two natural rubber vulcanizates, which had been subjected to isothermal anaerobic aging. Thermal aging was performed on two different natural rubber vulcanizates. The thermal aging was conducted between the temperatures of 80 and 120°C for times ranging from 3 to 24 days. The effect of thermal degradation was measured from the changes in the chemical composition of the vulcanizates as functions of time at temperature. A master curve relationship between the changes in the chemical composition of the vulcanizates due to thermal degradation and their static and dynamic mechanical properties has been developed. This relationship allowed for the prediction of the vulcanizate mechanical properties after thermal aging. It was found that the mechanical properties correlated with the percentage of poly and monosulfidic crosslinks, where in general higher levels of polysulfidic crosslink gave rise to the highest mechanical properties.
Crack propagation in an aged and unaged natural rubber vulcanizate was measured using a double cantilever beam, DCB. This type of testing arrangement exhibits a plane strain condition and resulted in crack growth rates two orders of magnitude faster than traditional plane stress testing geometries. To validate the DCB specimens, an investigation into the potential cavitation inside the rubber of the DCB specimens was performed. It was found that no cavitation occurred due to the high speed of the fracture. DCB samples were thermally aged to determine the effect of thermal aging upon the crack growth rate. It was found that crack growth rates increase with thermal aging.
Life prediction of the aged 2-ply laminates was performed using a finite element analysis. In order to verify the finite element models used in the life prediction, the fatigue failure and crack growth characteristics of off axis 2-ply cord-rubber laminates were examined with a delamination analysis. This analysis allowed for the determination of the modulus of off axis 2-ply laminates in the presence of damage as well as the calculation of the crack growth rates of the laminate. The failure of unaged and thermally aged 2-ply laminates was evaluated and compared to the crack growth rates of thermally aged DCB specimens. The trend due to thermal aging between the two types of testing specimens was consistent.
The finite element analysis was sectioned into two approaches: crack initiation and crack propagation. The former utilized a residual strength approach, while the latter applied a fracture mechanics approach. The predicted stress versus cycles, S-N, curves were not in complete agreement with the experimental data. The error between the predicted and the experimental is discussed and future work to correct that error is suggested. While there was not complete agreement between the predicted and the experimental data, this dissertation outlines a comprehensive approach to track the effects of thermal degradation and apply those effects to a real world application.Ph. D.
8
Khunkamchoo, Prasert. "Inter-property relationships for natural rubber compounds." Thesis, Loughborough University, 1993. https://dspace.lboro.ac.uk/2134/28206.
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The present work was initiated in order to develop an improved understanding of the effect of crosslink density, carbon black dispersion and rheological properties on the stiffness and fracture properties of natural rubber vulcanisates.
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Mohammed, Nor Hussin Bin. "Telechelic natural rubber oligomers via controlled ozonolysis." Thesis, Lancaster University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306916.
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Chiang, Cheng Ching Kurt. "Natural Rubber Biosynthesis: Perspectives from Polymer Chemistry." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1386367354.
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Norwood, Verrill M. IV. "Introduction of Natural Oils into Rubber Compounds." Digital Commons @ East Tennessee State University, 2014. https://dc.etsu.edu/honors/198.
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In the rubber industry, plasticizers for rubber compounds mainly consist of petroleum derivatives. Consequently, the rubber industry is in constant competition with many petroleum consumers. This competition places an economic strain on rubber companies such as HEXPOL RUBBER COMPOUNDING L.L.C. In order to alleviate this strain, natural oil alternatives to petroleum plasticizers are of novel research interest and are investigated in this thesis project.
12
Brown, Daniel. "Investigating the biosynthesis of natural rubber through the characterisation of rubber associated proteins." Thesis, University of Warwick, 2016. http://wrap.warwick.ac.uk/88568/.
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Natural rubber from the para rubber tree Hevea brasiliensis is one of world’s most important natural resources. Despite its use in the manufacture of a wide range of essential items the mechanisms by which natural rubber is synthesised is poorly understood. Natural rubber is a long chain cis-polyisoprene, composed of units of isopentenyl pyrophosphate (IPP) which is contained within rubber particles. Rubber particles consist of a hydrophobic polyisoprene interior surrounded by a monolayer membrane. Due to the insoluble nature of rubber the only place that polymerisation could occur is on this membrane by a hypothetical membrane bound rubber transferase. Whether this is a single enzyme or complex is currently unknown. Cis-prenyltransferases (CPTs) are a group of enzymes responsible for the polymerisation of cis-polyisoprene. The first plant CPTs were identified in Arabidopsis which paved the way for the identification of two Hevea CPTs, HRT1 and HRT2. HRT2 is able catalyse the formation of long chain polyisoprene products in the presence of rubber particles and is the focus of this thesis. Hevea takes at least 4 years to reach maturity. Its long life cycle coupled with the difficulty of genetic transformation meant that direct study on Hevea was not feasible for this project. Instead transient expression in N. benthamiana as well as some preliminary work in L. sativa was used to characterise rubber associated proteins. HRT2 was found to be a cytosolic protein and in theory incapable of polymerising natural rubber on the surface of rubber particles. The scope of the project was therefore widened to include possible interactors that could act to bring it to a membrane. These interactors were identified and cloned based on existing literature and included small rubber particle protein (SRPP), rubber elongation factor (REF), rubber biosynthesis stimulator protein (RBSP) and a newly characterised cis-prenyltransferase like (CPTL) protein, HevNogo. Whilst HRT2 on its own was unable to associate with a membrane, expression with HevNogo induced its subsequent localisation to the plasma membrane. This interaction initially took place on the endoplasmic reticulum. The HRT2/HevNogo complex may be part of a rubber transferase complex, however it is likely that additional components are required.
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Ren, Xianjie ren. "Improving sustainability of rubber composites with renewable additives and epoxidized guayule natural rubber." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1574440536318129.
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Hariwongsanupab, Nuttapong. "Development of green natural rubber composites : Effect of nitrile rubber, fiber surface treatment and carbon black on properties of pineapple leaf fiber reinforced natural rubber composites." Thesis, Mulhouse, 2017. http://www.theses.fr/2017MULH0399/document.
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Les effets du caoutchouc nitrile (NBR), du traitement de la surface des fibres et du noir de carbone sur les propriétés des composites à base de caoutchouc naturel renforcé par des fibres d'ananas (NR / PALF) ont été étudiés. L'incorporation de NBR et le traitement de surface de la fibre ont été utilisés pour améliorer les propriétés mécaniques des composites à faible déformation, alors que le noir de carbone a été utilisé pour améliorer ces propriétés à forte déformation. La teneur en fibres a été fixée à 10 phr. Les matériaux composites ont été préparés à l'aide d'un mélangeur à cylindres et ont été réticulés sous presse permettant ainsi le maintien de l'orientation des fibres. Ces composites ont été caractérisés à l’aide du rhéomètre à matrice mobile (MDR), par analyse thermique mécanique dynamique (DMTA) et par tests de traction. La morphologie après fracture cryogénique a été observée à l'aide de la microscopie électronique à balayage (MEB). L'effet du NBR dont la teneur varie de 0 à 20 phr par rapport à la teneur totale en caoutchouc, a été également étudié. Le NBR est utilisé afin d’encapsuler totalement les fibres d’ananas (PALF) ; ceci conduisant à un meilleur transfert de contraintes entre la matrice et les fibres. La méthode de mélange a également été étudiée. Plusieurs types de silanes tels que le propylsilane, l'allylsilane et le silane-69 ont été utilisés pour traiter les fibres pré-nettoyées à l’aide d’un traitement alcalin. Les fibres silanisées ont été caractérisées par spectroscopie infrarouge à transformée de Fourier (FTIR), par spectroscopie de photoélectrons aux rayons X (XPS) et par MEB. Le traitement de la fibre par le silane-69 a permis d’augmenter fortement le module du matériau composite à faible déformation. Ce traitement a été plus efficace que l'incorporation de NBR dans les composites NR / PALF. Ceci peut s’expliquer par une possible réticulation chimique entre le caoutchouc et la fibre traitée au silane-69 plutôt qu’une simple interaction physique du NR, du NBR et de la fibre. Cependant, le renforcement par fibre réduit la déformation à la rupture. Par conséquent, du noir de carbone a également été incorporé dans les composites NR/NBR/PALF et NR/ PALF traitée, afin d’améliorer leurs propriétés ultimes. En incorporant du noir de carbone à un taux de 30 phr dans les deux composites, les propriétés mécaniques des composites ont été améliorées et peuvent être contrôlées à la fois à des déformations faibles et hautesThe effects of nitrile rubber (NBR), fiber surface treatment and carbon black on properties of pineapple leaf fiber-reinforced natural rubber composites (NR/PALF) were studied. The incorporation of NBR and surface treatment of fiber were used to improve the mechanical properties of composites at low deformation, whereas carbon black was used to improve these properties at high deformation. The fiber content was fixed at 10 phr. The composites were prepared using two-roll mill and were cured using compression moulding with keeping the fiber orientation. These composites were characterized using moving die rheometer (MDR), dynamic mechanical thermal analysis (DMTA) and tensile testing. The morphology after cryogenic fracture was observed using scanning electron microscopy (SEM). The effect of NBR from 0 to 20 phr of total rubber content was investigated. NBR is proposed to encase PALF leading to higher stress transfer between matrix and PALF. The method of mixing was also studied. For the fiber surface treatment, propylsilane, allylsilane and silane-69 were treated on the alkali-treated fiber. Treated fibers were characterized using Fourier-Transform infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS) and SEM. Silane-69 treatment of fiber increased the modulus at low deformation more than the incorporation of NBR of NR/PALF composites due to the chemical crosslinking between rubber and fiber from silane-69 treatment rather than the physical interaction of NR, NBR and fiber. However, reinforcement by fiber reduced the deformation at break. Hence, carbon black was also incorporated into NR/NBR/PALF and NR/surface-treated PALF composites to improve the ultimate properties. By incorporation of carbon black 30 phr in both composites, the mechanical properties of composites were improved and can be controlled at both low and high deformations
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Soontaranurak, Kittikorn. "Supply response of natural rubber production in Thailand." Thesis, University of Newcastle Upon Tyne, 2011. http://hdl.handle.net/10443/1253.
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In the Thai economy, natural rubber is a major export crop and the natural rubber sector is an important source of employment. A key issue in the analysis of natural rubber production is its supply response to economic incentives. There are several empirical studies of the supply response of natural rubber in Thailand, but knowledge gaps exist. First, since most apply Nerlovian models, their models have an inadequate dynamic structure. Second, ordinary least squares is generally applied to potentially non-stationary data, so the results may be spurious. Third, the results may be biased because many studies omitted important variables. Finally, there is no consideration of risk. It is essential to seek alternative explanations of what and how both price and non-price factors cause changes in natural rubber production using modern econometric approaches and contemporary data. Economic theory implies that the supply of a perennial crop depends on own price, the prices of competitive crops, input prices, and non-price variables, and risk and uncertainty. The time series data on these variables are examined for unit roots. Most variables are non-stationary and Johansen‟s cointegration approach is used to estimate both output and acreage-yield models. We find that unique long-run relationships exist in both models. However, weak exogeneity tests show that the rubber price in both the output and acreage equations is weakly exogenous. We therefore reformulate the output and acreage equations by setting rubber price to be weakly exogenous. Output in the output model is now weakly exogenous and there is no long-run output relationship. Thus, an output supply response model appears inappropriate to explain the supply response of rubber production of Thailand. In the acreage response model, vi we find a unique long-run relationship between the planted area and the rubber and fertiliser price. Results indicate that the estimated long-run own price elasticity of rubber planted acreage is 2.16, which is higher than those in previous studies, while the elasticity of rubber planted acreage in response to a change in the replanting subsidy is estimated to be 0.65. The estimated short-run price elasticity of rubber planted acreage is very low at 0.03. We also find that there is a unique long-run relationship between yield, the fertiliser price, and rainfall, but non-normal residuals might affect statistical inference. The long-run elasticity of yield with respect to the fertiliser price is estimated to be -5.50 while own price has no effect on yield. Rainfall has a negative effect on yield. Impulse response analysis shows that a shock in the replanting subsidy leads to a continual increase in acreage, and this might imply instability of the model. A one standard error shock in the fertiliser price causes a decrease of 7% in the yield; this effect is permanent and yield takes around seven years to restore to long-run equilibrium. Our estimates suggest that farmers in Thailand respond to price incentives. Low estimated short-run and high estimated long-run price elasticities of acreage response imply that rubber farmers only adjust planted area in the short run in response to a price change by a small amount, whereas they make substantial adjustments in the long run. Therefore, any form of pricing policy requires a long lead time to take effect. Since small increases in the price of rubber lead to large increases in the planted rubber acreage, if the government aims to increase rubber acreage, the rubber price should not be allowed to fall. The government should develop domestic markets particularly central rubber markets, encourage the establishment of farmer groups, stimulate more domestic demand, and co-operate with other rubber producing vii countries to intervene in the world market. Moreover, the government can stimulate the expansion of acreage planted in the long run by increasing the replanting subsidy. In our yield response model, the policy implication is that a sufficient amount of good quality fertiliser at reasonable prices should be provided. Also, the government should support research and development into rubber cultivation and harvesting, particularly those on integrated plantation, and then disseminate this knowledge to farmers.
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Smeaton, Jacqueline. "Study of postvulcanisation of natural rubber latex films." Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/6985.
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Tensile strength-modulus relationships established for postvulcanised latex films have been found to show characteristics of both prevulcanised latex and dry rubber curves. The curves depend upon the accelerator system used, as with dry rubber. They passed through their maxima after which tensile strength fell, with the down-turn less pronounced than for prevulcanised latex but greater than for dry rubber. The results suggest that postvulcanised latex films remain particulate rather than homogeneous. Processes known to affect prevulcanised latex films were applied to postvulcanised latex films. These included stirring and maturation of latex, different conditions for drying films and leaching with water and solvents, but only stirring had a significant effect. Stirring was essential to produce homogeneous latices for films with consistent chemical compositions and physical properties.
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Chen, Linling. "Tear Energy of Natural Rubber Under Dynamic Loading." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1227728603.
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Jiang, Jiali. "Tearing of Black-Filled (N660) Natural Rubber Vulcanizates." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1349395720.
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Hong, Yang. "Tearing of Black-filled (N330) Natural Rubber Vulcanizates." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1428194782.
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Sugimoto, Kenichi. "Mechanisms of antifatigue agents used in natural rubber." Thesis, Aston University, 1995. http://publications.aston.ac.uk/9755/.
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A large number of compounds containing quinonoid or hindered phenol functions were examined for their roles as antifatigue agents. Among the evaluated quinones and phenols expected to have macroalkyl radical scavenging ability, BQ, TOC, TOC and GM showed relatively good performance for fatigue resistance (although their performance was slightly less effective than the commercial aromatic amine antioxidants, IPPD and 6PPD). The compounds which were shown to have higher reactivity with alkyl radicals (via calculated reactivity indices) showed better fatigue resistance. This fact supports the suggestion that strong alkyl radical scavengers should be also effective antifatigue agents. Evidence produced based on calculation of reactivity indices suggests that the quinones examined react with alkyl radicals on the meta position of the quinone rings producing phenoxyl radicals. The phenoxyl radicals are expected either to disproportionate, to recombine with a further alkyl radical, or to abstract a hydrogen from another alkyl radical producing an olefine. The regeneration of quinones and formation of the corresponding phenols is expected to occur during the antifatigue activity. The phenol antioxidant, HBA is expected to produce a quinonoid compound and this is also expected to function in a similar way to other quinones. Another phenol, GM, which is also known to scavenge alkyl radicals showed good antifatigue performance. Tocopherols had effective antifatigue activity and are expected to have different antifatigue mechanisms from that of other quinones, hence TOC was examined for its mechanisms during rubber fatiguing using HPLC analysis. Trimers of TOC which were produced during vulcanisation are suggested to contribute to the fatigue activity observed. The evidence suggests that the trimers reproduce TOC and a mechanism was proposed. Although antifatigue agents evaluated showed antifatigue activity, most of them had poor thermoxidative resistance, hence it was necessary to compensate for this by using a combination of antioxidants with the antifatigue agents.
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Grange, Jérémie. "Functionalization of polyisoprene : toward the mimic of natural rubber." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0004/document.
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Ce travail de thèse porte, de manière globale, sur une meilleure compréhension du caoutchoucnaturel (NR). En effet, bien que ce matériau soit fortement utilisé dans l’industrie et ce depuisdes dizaines d’années, plusieurs de ses propriétés restent à ce jour mal comprises.Antérieurement à nos travaux, il a été fait un lien entre la biosynthèse du polymère et cespropriétés et il a été proposé que le caoutchouc naturel était constitué d’une chaînepolyisoprène (PI) 100% 1,4-cis de forte masse molaire (> 500 000 g/mol) fonctionnalisée en αet ω par une protéine et un motif phospholipidique respectivement. Ces bouts de chaîneseraient capables de s’auto-assembler pour créer un réseau physique qui confère au NR sespropriétés si intéressantes. L’objet de cette thèse a donc été de synthétiser un copolymère triblocProtéine/PI/Lipides afin de confirmer cette hypothèse en produisant en laboratoire unhomologue de NR. Pour ce faire, un PI hétéro-téléchélique cétone/aldéhyde a été obtenu pardégradation chimique de NR. Cette méthode a permis d’obtenir un PI 100 % 1,4-cis possédantdeux fonctions chimiques différentes en bout de chaine permettant ainsi le greffage sélectifd’une protéine où d’un motif lipidique. Ces deux couplages ont ensuite été étudiés séparément(PI/Protéine puis PI/Lipides) révélant des propriétés intéressantes dans le cas du copolymèredi-bloc PI/Lipide. Le couplage PI/Protéine s’est avéré plus compliqué et seul des copolymèresdi-blocs PI/Polypeptide ont pu être obtenus avec certitude, en utilisant des synthons PI commemacro-amorceurs. Une voie de synthèse a également été dégagée pour un tri-blockPolypeptide/PI/Lipide présentant une structure très proche du modèle de TanakaThis PhD work focuses on a better comprehension of natural rubber (NR). Indeed, despite thefact that this material has been used for a long time in industry, some properties remainunclear. Previous works of Tanaka allowed to make a link between the biosynthesis of thematerial and its properties. It was thus suggested that NR was composed of a high molar masschain of polyisoprene (PI, > 500 000 g/mol) functionalized at the α and ω chain-end by aprotein and a phospholipidic moiety respectively. These chain-ends would be able to selfassembleinto a pseudo-physical network which would explain some of the superior propertiesof NR. The goal of this PhD work is to synthesize a Protein/PI/Lipid tri-block copolymer inorder to check this hypothesis and to synthesize hybrid material close to NR. First, a 1,4-cishetero-telechelic (ketone/aldehyde) PI of 10 000 g/mol was obtained by chemical degradationof NR, yielding a polymeric chain bearing two different functions at the chain-ends, allowingto perform a selective functionalization with both a lipidic moiety and a protein. Both di-blockcopolymers (PI/Lipid and PI/Protein) were synthesized and studied separately. The PI/Lipiddi-block copolymer revealed interesting properties. The synthesis of PI/Protein di-blockcopolymer revealed more difficult and only PI/Polypeptide di-block copolymer could havebeen obtainded. To this end, PI macro-initiator allowed the Ring-Opening Polymerization odN-carboxyanhydride. Finally, a chemical pathway was established, allowing to synthesize aPolypeptide/PI/Lipid tri-block close to Tanaka’s model
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Foster, Kennith E., N. Gene Wright, and Susan Fitzgerald Fansler. "Guayule Natural Rubber Commercialization: A Scale-Up Feasibility Study." Office of Arid Lands Studies, University of Arizona (Tucson, AZ), 1991. http://hdl.handle.net/10150/303352.
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Conducted under USDA Agreement No. 58-3159-7-11 Guayule Natural Rubber ProgramIntroduction: The United States imports 100 percent of its natural rubber. Ninety-two percent of our natural rubber production is concentrated in Southeast Asia, which is subject to interruptions through political action or direct military intervention. Natural rubber, a critical and strategic material, is necessary in such articles as aircraft and ground vehicle tires, medical supplies, resilient mounts, and certain acoustical applications. Synthetic elastomers cannot meet performance requirements in these areas. A domestic source of natural rubber will assist in assuring a supply of this critical material for industry and defense. The U.S. Department of Defense (DoD) and the U.S. Department of Agriculture (USDA) signed a Master Memorandum of Understanding in 1982 that calls for cooperation with respect to food, agriculture, forestry, nutrition, and other research of mutual interest. With this MOU both agencies adopted a supplemental agreement in 1986 that initiated the Joint Guayule Domestic Rubber Program, whose ultimate goal is to promote an economically viable domestic guayule rubber industry. To accomplish this goal, both agencies have provided funding to plant and cultivate guayule shrubs, construct a 150 -long- ton -per -year prototype plant to extract rubber from the shrubs, and conduct evaluations to establish the performance capability of military products fabricated with domestic guayule rubber. A critical component of the supplemental agreement calls for the USDA to assess the feasibility of a commercial guayule rubber processing facility of 50,000-long-ton-per-year nameplace capacity. This report, based on the best available data (1990) and on assumptions of future advancements in technology (for 1996), is designed to address the commercial prospects for the establishment of a domestic guayule rubber industry. It also examines the feasibility and factors involved in meeting either 20 percent or 100 percent of the natural rubber needs of the U.S. Department of Defense in both peacetime and national emergency conditions.
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Hu, Jiahuan. "Strain-Induced Crystallization of Natural Rubber and Isoprene Rubber Studied by Solid-State NMR Spectroscopy." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1397087771.
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Lucchese, Laurence. "High temperature stabilisation of carbon black filled natural rubber." Thesis, Manchester Metropolitan University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310622.
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Sagoo, P. S. "Vapour transport in natural rubber blends and graft copolymers." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37842.
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Jaafar, Rosly. "Ultrasonic non-destructive evaluation of natural rubber latex suspensions." Thesis, Keele University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318988.
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This thesis describes the development of wide bandwidth ultrasonic pulse transmission and pulse echo comparison spectrometer methods to measure the ultrasonic phase velocity and absorption in natural rubber latex. Details of the quantitative design and construction of simple prototype test rigs include the mechanism of: variable path length pulse transmission, variable path length reflected pulse echo, and dual transducers reflected pulse echo. Special signal processing of experimental data, including transducer impulse response correction routines to calculate the acoustical parameters, are outlined. Measurements made using the constructed prototype test rigs are compared with each other and with data available in the pulished literature. A selection of methods to suit varying requirements for acoustical measurements in natural rubber latex samples is made. Calibration curves relating the measured ultrasonic absorption and phase velocity with the dry rubber content (d.r.c.) at temperatures of 20 to 30°C were constructed. Experiments to test the usefulness of these calibration curves were undertaken to determine if there was any deviation from the Standard Laboratory Method. A comparison between the experimental results obtained using the dual transducer reflected pulse method and the simulation of the Allegra and Hawley model with multiple scattering is presented. Good agreement was obtained between the experimental and the theoritical approaches up to 40% d.r.c. The feasibility of the detection of adulterant materials in natural rubber latex concentrates by using an ultrasonic method is discussed. Finally, the dual transducers reflected pulse echo technique is found be an alternative method to determine d.r.c. in natural rubber latex and could be used as a real time monitoring system for liquids and suspensions in a production environment.
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Samran, Jareerat. "A study of non-catalytic hydrogenation of natural rubber." Le Mans, 2005. http://cyberdoc.univ-lemans.fr/theses/2005/2005LEMA1022.pdf.
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Cette étude aborde l'hydrogénation du caoutchouc naturel dans un but de développement et de valorisation de cette substance largement produite dans le sud-est asiatique et en particulier en Thaïlande. En effet, ce composé est un polymère insaturé bien connu, possédant d'excellentes propriétés élastiques, mais sa résistance en température est nettement inférieure aux élastomères synthétiques. Dans ce travail, l'hydrogénation a été menée par voie non catalytique, en utilisant un agent intermédiaire de type diimide généré in-situ à partir de deux types de composés, à savoir i) la décomposition thermique du p-toluensulfonnylhydrazide (TSH) ainsi que ii) la réaction de l'hydrazine (N2H4) et l'hydroperoxide (H202) en présence d'un catalyseur. La structure des caoutchoucs hydrogénés a été analysée par différentes méthodes spectroscopiques : absorption infrarouge, diffusion Raman, RMN en phase liquide et solide. L'hydrogénation du caoutchouc naturel et de sa forme époxyde a été réalisée à l'aide de TSH dans une solution de xylène à l35°C. Un ratio molaire [TSH] :[C=C] de 2 a été choisi pour l'hydrogénation du caoutchouc naturel et de 4 formes époxydes contenant respectivement 10,22,30 et 40% d'époxyde. Les mesures quantitatives menées par les différentes techniques spectroscopiques sont toutes concordantes et indiquent une augmentation du taux d'hydrogénation avec le temps de réaction pour atteindre des valeurs limites proches de 90% pour un temps de réaction égal à 8h. L'isomérisation cis-trans a été observée par RMN en phase liquide et solide. En outre des réactions secondaires peuvent apparaître, dues aux températures élevées des protocoles utilisés. Dans le cas de l'utilisation de N2H4 et de H2O2, l'hydrogénation a été réalisée directement sur la forme latex du caoutchouc naturel, avec étude de l'influence de divers paramètres : temps de réaction, température, taux des réactifs. Le suivi du taux d'hydrogénation par RMN liquide montre que les meilleurs résultats sont obtenus pour des rapports équimolaires de N2H4 et de H2O2. Les caractéristiques moléculaires du caoutchouc naturel, de la forme époxyde à 10% et des différents composés hydrogénés a été complètement étudiée par diffusion Raman et RMN du carbone 13e. La diffusion Raman montre l'augmentation de la constante de force associée à la double liaison C=C en fonction du taux d'hydrogénation, qu'il est possible d'associer à un accroissement de la rigidité de la structure d'ensemble. L'étude thermique effectuée par DSC révèle une amélioration des propriétés des échantillons après hydrogénation tant en solution que pour les systèmes en phase aqueuse. La comparaison des propriétés de stabilité thermique des caoutchoucs naturels hydrogénés, par analyse thermogravimétrique, sous air ou sous atmosphère d'azote montre que la décomposition en température est plus faible sous air. De même les propriétés thermiques des formes époxydes ont été améliorées après hydrogénation. L'ensemble des matériaux également fait l'objet d'une étude rhéologique complète. Enfin la technique d'imagerie Raman révèle que l'hydrogénation est un processus aléatoire au moins à l'échelle micrométriqueHydrogenation is one of the most efficient methods to alter and improve the physical properties of unsaturated polymers and to produce a new material. The aim of this research is to transform partially the unsaturated part of natural rubber (NR) into saturated moiety in order to improve its thermal and oxidative properties and to widen its area of applications. In this study, non-catalytic hydrogenation process was applied by using diimide generated in situ from two types of hydrogenating agent i. E. Thermal decomposition of p-tolueriesulfonylhydrazide (TSH) and oxidation of hydrazine (N2H4) by hydrogen peroxide (H2O2). The chemical structure of the hydrogenated rubbers was analyzed by vibrational and resonance spectroscopies i. E. FTIR, Raman, 1H- and 13C-NMR. First, the hydrogenation of NR and its modified form as epoxidized NR (ENR) was performed by using TSH in xylene solution at 135°C. The molar ratio of [TSH]:[C=C] equal to 2 was used for hydrogenation of NR and four different types of ENR i. E. ENR-10, ENR-22, ENR-30 and ENR-40, containing 10, 22, 30 and 40% mole of epoxide content, respectively. The quantitative measurements on fraction of saturated units determined by Raman, 1H-NMR in liquid state and 13C-NMR in solid state gave similar results which indicated that percent hydrogenation increased with increasing reaction time and about 80-89 % hydrogenation was obtained at 8h. While in the case of ENRs, the percent hydrogenation is approximately 93-98%. Cis-trans isomerization was also observed by 1H-NMR in liquid state and 13C_NMR both in liquid and solid state. Sorne side reaction occurred i. E. Chain degradation of both NR and ENRs which might be due to a relatively high temperature process. In the case of hydrogenation of ENRs, formation of furan structure and fixation of p-toluenesulfinic acid (TSOH) by-product were detected by FTIR. For hydrogenation using (N2H4) and (H2O2), NR in the original form of latex was used. Various parameters affecting the hydrogenation reaction were investigated i. E. Reaction time and temperature, amount of reactants, and dry rubber content. The hydrogenation progress could be monitored by means of NMR in liquid state as function of reaction condition. The results indicated that the best result was obtained when equimolar ratio of (N2H4) and (H2O2) was used. With addition of varying hydrazine and hydrogen peroxide contents, the best condition of diimide reduction is achieved when their content is 1. 5 times the amount C=C of the rubber. Molecular characteristics in the NR, ENR-l 0 and the hydrogenated rubbers were investigated by Raman and 13C-NMR in solid state techniques. The relative variation force constant as analyzed by Raman spectroscopy tends to increase with the hydrogenation level. It might be suggested that the higher stiffness of the rubber chains upon hydrogenation is correlated to the increased relative variation force constants. In cross-polarization (CP) experiment of HNR and HENR, it was found that the rate of cross polarization of methyl carbon in HENR-30(8) is highest with respect to methyl carbon in HNR(8) and HENR-IO(8). It is clear that the methyl carbon of HENR-30(8) has the least mobility due to more furan units and chemical fixation of TSOH on the rubber chains. Thermal properties studied by a differential scanning calorimetry revealed thermal improvement after hydrogenation, both in solution and in aqueous systems. Comparison of the thermal stability using thermogravimetric analyzer, under air and nitrogen atmosphere, showed the decomposition temperature of HNR in air is lower than that in nitrogen atmosphere. The thermal stability of ENR was also enhanced after hydrogenation. Rheological properties of HNR samples measured using RPA rheometer exhibited the storage and loss moduli of HNR97 sample with the highest value compared to HNR38 and HNR69 samples. For instance, the fully hydrogenated NR has a significant increment in the loss and storage moduli of the samples. By using Raman mapping technique, it revealed that the hydrogenation of NR is a random process at the micron level
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Pianhanuruk, Ekkawit. "Natural rubber grades, from polymer characteristics to engineering properties." Le Mans, 2010. http://cyberdoc.univ-lemans.fr/theses/2010/2010LEMA1026.pdf.
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Cette thèse s’intéresse aux relations entre les caractéristiques du Caoutchouc Naturel, ses propriétés de mise en oeuvre et les propriétés mécaniques d’échantillons vulcanisés, en considérant une sélection de grades représentatifs. Des techniques de spectroscopie, physicochimiques et de rhéologie ont été utilisées, ainsi que des mesures de propriétés mécaniques sur des mélanges vulcanisés. Les résultats montrent que, telles quelles, les techniques spectroscopiques ne révèlent pratiquement aucune différence entre les divers grades étudiés. Cependant, en utilisant une technique de polarisation croisée de l’angle magique de spin 13C, on peut distinguer les composants mobiles et immobiles qui montrent des différences entre les grades. Les grades feuilles fumées (RSS) ont les taux de gel les plus élevés, en accord avec leur masse molaire, leur viscosité Mooney et leur module complexe. Parce qu’elle fournit des informations détaillées sur le comportement viscoélastique non-linéaire, la rhéométrie à Transformée de Fourier se révèle capable de discerner les différents grades étudiés. Par exemple, tous les grades présentent une région linéaire jusqu’environ 60% de déformation mais les échantillons de RSS montrent une non-linéarité intrinsèque (c. A. D. Induite par la structure du matériau) tandis que les grades à viscosité stabilisée sont extrinsèquement non-linéaire (nonlinéarité induite par la déformation), comme la plupart des polymères simples. Les effets de mastication ont été étudiés sur des échantillons de RSS3 et de SMR10CV60 et on a trouvé que les premiers requièrent plus d’énergie que les derniers. La viscosité Mooney et la masse molaire décroissent avec l’augmentation de l’énergie de mélangeage. Il apparaît que la mastication détruit le contenu en gel, de sorte que le module complexe diminue, de même que la sensibilité à l’histoire du cisaillement. Les mélanges chargés au noir de carbone avec les grades latex des champs (STR5L, RSS3 et RSS3E) ont des modules complexes plus élevés que les grades à viscosité stabilisée (OMNR, STR5CV60 et SMR10CV). Pour une même formule, mais des grades différents de caoutchouc naturel, les propriétés physiques des caoutchoucs vulcanisés ne montrent aucune différence significativeThis thesis investigates the relationships between the characteristics of Natural Rubber, its processing properties and the mechanical properties of vulcanized specimens by using a selection of representative grades. Spectroscopic, physico-chemical and rheological techniques were used, as well as mechanical testing of vulcanized compounds. Results show that, as such, spectroscopic techniques are not able to reveal significant differences between the various investigated NR grades. However, by using 13C cross-polarization magic angle spinning (CP-MAS) technique, mobile and immobile components can be distinguished, so highlighting differences between grades. Ribbed Smoked Sheet (RSS) grades exhibit the highest gel content, in agreement with molecular weight, Mooney viscosity and complex modulus. Thanks to the very detailed information it provides regarding the nonlinear viscoelastic behavior, Fourier Transform rheometry is shown to clearly distinguish between the various NR grades. For instance all tested samples exhibit a linear region up to around 60% strain but RSS samples exhibit intrinsic nonlinearity (i. E. Morphology-induced) whilst viscosity stabilized grades show essentially extrinsic non-linearity (i. E. Strain-induced), like most simple polymers. Mastication effects on samples of RSS3 and SMR10CV60 were studied and the former were found to require higher mixing energy than the latter. Mooney viscosity and molecular weight decrease with increasing mixing energy. The mastication process appears to destroy the gel content of NR, so that the complex modulus is decreased as well as all strain history sensitivity. Carbon Black filled compounds with field latex grades (STR5L, RSS3 and RSS3E) are found to exhibit higher complex modulus than viscosity stabilized grades (OMNR, STR5CV60 and SMR10CV). Physical properties of cured rubber for the same formula but different rubber samples show no significant difference
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Samran, Jareerat Phinyocheep Pranee. "A study of non-catalytic hydrogenation of natural rubber." [S.l.] : [s.n.], 2005. http://cyberdoc.univ-lemans.fr/theses/2005/2005LEMA1022.pdf.
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Reproduction de : Thèse de doctorat : Physique : Bangkok : 2005. Reproduction de : Thèse de doctorat : Physique : Le Mans : 2005.Thèse soutenue en co-tutelle. Titre provenant de l'écran-titre. Bibliogr. p. 274-282.
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Taksapattanakul, Korn. "Thermoplastic Vulcanizates Based on Hydrogenated Natural Rubber/Polypropylene Blends." Thesis, Le Mans, 2016. http://www.theses.fr/2016LEMA1028/document.
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La préparation du caoutchouc naturel hydrogéné (HNR) par réaction avec l'hydrazine et le peroxyde d'hydrogène et le latex de caoutchouc naturel a été intéressée. L’influence de conditions de réaction, types et volume de solvants, volume du réactionnel, la quantité d’hydrazine et de peroxyde d’hydrogène sur le degré d’hydrogénation du caoutchouc naturel a été étudiée. Le structure et détermination du degré d’hydrogénation des caoutchoucs naturel hydrogénés a été analysée par résonance magnétique nucléaire (RMN), transformée de fourier infrarouge (FTIR) et spectroscopie Raman. Un degré d'hydrogénation de 18 % a été obtenu à 1.0 - 2.0 du la molaire de d’hydrazine et de peroxyde d’hydrogène, température optimale de 50°C et le temps de réaction de 24h. Afin d'améliorer le degré d'hydrogénation, des solvants tels que le toluène et le hexane et l'effet de le volume du réactionnel ont été étudiée, ce qui a permis d'obtenir des degrés d’hydrogénation élevés (proches de 65% avec le toluène). D’autre part, des mesures de tailles de particules de latex ont montré que l’hydrogénation du caoutchouc naturel n’avait pas d’effet sur latex de caoutchouc naturel. Un résultat également intéressant concerne le détermination du taux de gel. Ce gel augmente avec le degré d’hydrogénation, prouvant que des réactions de réticulation ont eu lieu. Néanmoins aucun effet de degré d’hydrogénation sur le température de transition vitreuse n’est détecté. La dureté et viscosités Mooney augmentent, en lien avec l’augmentation du taux de gel. Par ailleurs, la résistance thermique du caoutchouc naturel hydrogéné est considérablement améliorée lorsque le degré d’hydrogénation augmente. Le partie suivante est consacrée à la vulcanisation du caoutchouc. Deux types de réticulation ont été utilisés : au soufre et au peroxyde. Les élastomères HNR réticulés montrent une meilleure résistance à l’ozone et l’UV que le NR réticulé. De plus, cette résistance à l’ozone et l’UV est plus élevée pour le réticulation au soufre, comparée à le réticulation au peroxyde. Une bonne corrélation entre les images de microscopie optique et les résultats des analyses Raman est obtenue. La préparation et l’étude de mélanges HNR/PP obtenus par vulcanisation dynamique en utilisant du peroxyde et du soufre comme agents de réticulation. Un degré d’hydrogénation de 65% a été choisi, et différentes ratio HNR/PP ont été étudiés, et comparés avec des mélanges NR/PP. La morphologie des mélanges a été caractérisée par spectroscopie Raman, ce qui a permis d’obtenir des images cartographie Raman indiquant de façon précise le localisation et la distribution des phases de caoutchouc et de PP. Une bonne corrélation entre le cartographie Raman et les images de microscopie électronique à balayage (SEM) est obtenue. Ainsi il apparaît que les particules de caoutchouc sont dispersées dans une phase continue de PP, ceci à la fois pour le HNR et le NR. L’étude des propriétés mécaniques a montré que celles-ci étaient gouvernées principalement par le phase continue de PPThe non-catalytic hydrogenation of natural rubber latex (NRL) was carried out by using diimide generated in situ from the reaction between hydrazine (N2H4) and hydrogen peroxide (H2O2). The effects of mole ratios of [C=C]:[N2H4]:[H2O2], reaction conditions, solvent types, solvent volumes and reaction scale-up on the hydrogenation levels were investigated. Nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), and Raman spectroscopic techniques were employed to investigate the chemical structure of the hydrogenated natural rubber (HNRs) and to quantify the hydrogenationlevels. It was found that variations in moles of N2H4 and H2O2 in the range of 1.0-2.0 moles resulted in degrees of hydrogenation in the range of 10-18%. Little improvement in hydrogenation levels of HNRs was obtained when NRL particles were swollen in solvents by which toluene yielded better results than hexane. The increase in toluenevolume resulted in the increase in hydrogenation levels up to 42 %. TEM micrographs revealed that swelling mainly occurred at the surface of NRL particles, implying that hydrogenation reaction confined largely at the surface of NRL particles. After removal of toluene, particle size and particle size distribution of partially hydrogenated NRL remained unchanged. To further improve degrees of hydrogenation, the reaction volume was extended and 65% hydrogenation levels were obtained. Therefore, 14%HNR, 33%HNR, and 65%HNR were successfully prepared under suitable reaction conditions. However, crosslinking and cis-trans isomerization were side-reactions occurring during hydrogenation. Gel and trans contents increased with increasing hydrogenation levels, leading to the increase in hardness of HNRs. Mooney viscosities of HNRs increased with increasing degrees of hydrogenation due to the increased gel contents. Mooney torquerelaxation of NR and HNRs were similar. Thermogravimetric analysis revealed that vi HNRs had greater thermal stability than NR and thermal stability increased with increasing degrees of hydrogenation. HNR vulcanizates were much better resistant to ozone and UV than cured NR. Sulfur-vulcanized rubbers had greater ozone resistance than peroxide-cure rubbers due to less amounts of carbon-carbon double bonds present in rubbers. In addition, modulus at low strain and tensile strength of sulfur-cured rubbers were higher than those of peroxide-cured rubbers, but lower elongation due to higher crosslink densities. Also, modulus at low strain and tensile strength increased with increasing hydrogenation levels of HNRs, in contrast to strain at break. Thermoplastic vulcanizates (TPVs) from blends of HNR and Polypropylene (PP) were prepared via dynamic vulcanization using peroxide and sulfur as curing agents. The effects of blend ratios on mechanical properties of TPVs were investigated. Tensile strength increased with increasing PP portions, but breaking strain decreased. Morphology of TPVs was characterized with Raman mapping and scanning electron microscope (SEM). The phase sizes of crosslinked rubber obtained from both techniques were correlated well
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Al-Quraishi, Ali Abdul Hussain. "The Deformation and Fracture Energy of Natural Rubber Under High Strain Rates." University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1185471043.
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Choi, Jaesun. "Ultrasonically Aided Extrusion of Rubber Nanocomposites and Rubber Blends." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1362747207.
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Wang, Qinwei. "Effect of Tensile Rate and Carbon Black on the Fracture of Natural Rubber and Styrene-Butadiene Rubber." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1365778539.
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Gautriaud, Emilie. "Synthesis of polyisobutylene-polyisoprene diblock copolymer based on natural rubber biosynthesis." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1154963470.
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Heuwers, Benjamin [Verfasser]. "Shape Memory Natural Rubber - ein neuer umweltsensitiver Aktor / Benjamin Heuwers." München : Verlag Dr. Hut, 2013. http://d-nb.info/1042308462/34.
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Jayasuriya, Madhupani Mekhala. "Interpenetrating polymer networks based on natural rubber and poly(methylmethacrylate)." Thesis, Loughborough University, 2006. https://dspace.lboro.ac.uk/2134/33789.
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Several series of sequential interpenetrating polymer networks using natural rubber and poly(methylmethacrylate) were prepared. Three types of IPNs known as semi-1 IPNs, semi-2 IPNs and full IPNs have been prepared at various compositions. In addition, blends of natural rubber and poly(methylmethacrylate) were prepared for comparison. These materials have been characterized by dynamic mechanical thermal analysis, modulated temperature thermal differential scanning calorimetry, stress–strain analysis and some soxhlet extraction studies. The effects of composition and cross-linking of NR component and/or PMMA component on the physical and dynamic mechanical properties have been evaluated.
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Ohlemacher, Crittenden John. "Double Network Formation During Aging of a Natural Rubber Vulcanizate." University of Akron / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=akron1132327518.
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Barrera, Martinez Cindy Sofia. "Novel Renewable Materials from Natural Rubber and Agro-Industrial Residues." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1480540955796333.
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Poompradub, Sirilux. "Structure and physical properties of natural rubber based composite materials." 京都大学 (Kyoto University), 2005. http://hdl.handle.net/2433/144559.
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Lim, Jit Yang. "An evaluation of alternative forecasting models for natural rubber prices." Thesis, Curtin University, 2002. http://hdl.handle.net/20.500.11937/1731.
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One of the prominent features of the Natural Rubber (NR) market is its price variability, and the aim of this study is to project accurate short-term NR prices. This is accomplished by exploiting the use of forecasting techniques and information sets to seek the combination with the best forecasts, and exploring best ways of combining forecasts. We evaluate the relative performance of 19 models based upon three different forecasting techniques, and four information sets. In addition, we compare their forecasts with 13 other forecasts combined in various different ways, and taking the Naive forecast as benchmark. The generalised autoregressive conditional heteroscedasticity regression (or ARCH-type) models, though more complex, are generally better than the simpler regression models. In general, the performance of the various techniques seems to perform consistently well (or poorly) over the forecasting horizons, with alternations in performance due mainly to the type of information set used. We also adopted a simple trading rule to find out the economic values of our forecasts, and the results are most promising. Importantly, the forecasts generated from the alternative models developed in this study can potentially be beneficial to participants in the NR futures market.
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Lim, Jit Yang. "An evaluation of alternative forecasting models for natural rubber prices." Curtin University of Technology, School of Economics and Finance, 2002. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=13249.
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One of the prominent features of the Natural Rubber (NR) market is its price variability, and the aim of this study is to project accurate short-term NR prices. This is accomplished by exploiting the use of forecasting techniques and information sets to seek the combination with the best forecasts, and exploring best ways of combining forecasts. We evaluate the relative performance of 19 models based upon three different forecasting techniques, and four information sets. In addition, we compare their forecasts with 13 other forecasts combined in various different ways, and taking the Naive forecast as benchmark. The generalised autoregressive conditional heteroscedasticity regression (or ARCH-type) models, though more complex, are generally better than the simpler regression models. In general, the performance of the various techniques seems to perform consistently well (or poorly) over the forecasting horizons, with alternations in performance due mainly to the type of information set used. We also adopted a simple trading rule to find out the economic values of our forecasts, and the results are most promising. Importantly, the forecasts generated from the alternative models developed in this study can potentially be beneficial to participants in the NR futures market.
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Sukhawipat, Nathapong. "Synthesis of natural rubber based cationic waterborne polyurethane dispersion for adhesive applications." Thesis, Le Mans, 2018. http://www.theses.fr/2018LEMA1013/document.
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Synthèse de nouveaux WPU (waterborne polyurethane) cationiques à partir du caoutchouc naturel (NR), et évaluation de leurs propriétés adhésives pour des surfaces de type cuir. Ces WPU ont été obtenus par réaction du caoutchouc liquide hydroxy téléchélique (HTNR), de toluene-2,4-diisocyanate (TDI), N-methyl diethanol amine (NMDEA, en tant qu’émulsifiant) et d’éthylène glycol (EG, extenseur de chaîne). Ces structures biosourcés sont développés comme alternatives aux WPU issus des ressources fossiles à fort impact environnemental. Les effets de cinq paramètres ont été étudiés, à savoir la quantité d'émulsifiant (de 0 à 2,25 mole), celle d’éthylène glycol (de 0 à 3 moles), le Mn du HTNR (de 100 à 3000 g/mole), l'indice NCO (de 100 à 150) et le taux d’époxydation des HTNR précurseurs (de 0 à 30%). Il a été en outre démontré que la stabilité des dispersions aqueuses pour les formulations optimales dépassait les 10 mois. La géométrie des particules dispersées a été étudiée, démontrant un aspect sphérique et une taille à l'échelle nanométrique. Ainsi, plusieurs facteurs ont été étudiés pour évaluer les propriétés adhésives optimales sur bandes de cuir (Mn, pourcentage d’'époxyde). Des tests standard (Peel test et Lap Shear test) ont été utilisés et les valeurs obtenues comparées avec celles issus de formulations adhésives commerciales avec ou sans solvants. Au bilan, une formulation optimale a été déterminée (Mn = 3000 g/mole, LR epoxydation = 10%, NMDEA 5.67%wt, NCO index de 100 et 1 mole d’EG) avec cuisson préalable des systèmes à 70°C. Ce WPU a montré une force d’'adhésion supérieure à toutes les formulations commerciales testéesNovel cationic waterborne polyurethane (cWPU) based on natural rubber (NR) have been prepared by the polymerization reaction of hydroxyl telechelic natural rubber (HTNR), toluene-2,4-diisocyanate (TDI), N-methyl diethanol amine (NMDEA, as emulsifier), and ethylene glycol (EG, chain extender). The polyol structures have been developed as alternative to produce cWPUs derived from a renewable resource. The effects of five parameters were studied – amount of NMDEA (0 – 2.25 mole), amount of EG (0 – 3 mole), molecular weight of HTNR (~1000 – 3000 g/mole), NCO index (100 – 150), and epoxide content on eHTNR soft segment (0 – 30%). The appearance of cWPU dispersion was milky-blue with long shelf life time, more than 10 months. Particle of prepared cWPU were spherical shape in the nano range size. The adhesive properties of cWPUs on the real leather surface, taking into account of the different molecular weights of HTNR and different degree of epoxide content on HTNR, were tested by lap shear test and 180 degree peel test and compared with commercial adhesives. Overall, to balance the stability and adhesive strength, the best conditions for preparing cWPU adhesive for leather application in this study was from the composition of HTNR3000 with epoxide content of 10%, NMDEA 5.67%wt, NCO index of 100 and 1 mole of EG. in condition of curing at 70 °C. In comparison to non-solvent based and solvent based commercial adhesives, the adhesive strengths of these synthesized cWPU adhesive were superior
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Janchum, Nontasak. "Price risk management strategies in a natural rubber industry : a case study of rubber business intermediaries in Thailand." Thesis, Northumbria University, 2016. http://nrl.northumbria.ac.uk/30258/.
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Commodity prices have been more volatile in recent years. The volatility of prices widely impacts throughout the majority of stakeholder in commodity supply chains. Natural Rubber (NR) is one of the main exporting commodities in Thailand where millions of small farmers rely mainly on the NR producing to generate income for their living and children’s education. The existing literature relevant to commodity Price Risk Management (PRM) is dominated by developed countries in which markets have well-developed infrastructures. Although some research has been conducted in developing countries, most of it focuses on farmers or exporters whilst intermediaries who play a vital role as a middle tier in the supply chain are absent. In NR supply chains, the intermediaries are likely to be the ones who are exposed to the highest risk from price volatility. Their profit margins have diminished due to increasing market power of farmers and their greater accessibility to price information via the internet and mobile phone. Therefore, when NR prices become more fluctuated, the impact on Rubber Business Intermediary (RBI) businesses is even higher than beforehand. This research aims to explore the PRM strategies adopted, and to understand the PRM practiced by RBIs when it comes to managing their business in the south of Thailand. A qualitative method is used as a research approach in this study. 24 RBIs in seven provinces, including the three biggest NR producing provinces in Thailand, were targetted using semi-structured interview and pre-interview questionnaire methods. The interview data was analysed using the template analysis method and NVivo computer software. The findings highlight that the PRM strategies involved in the practices of RBIs are fragmented. This is due to the nature of the uncertainty in business circumstance, and the variety of the RBI’s personal profiles. The PRM strategies adopted by different types of RBIs are varied, as there are various supply chain structures. Moreover, there are even differences in their use amongst the same type of RBIs. This is mainly caused by the diversity in resources and PRM capability on the part of the RBIs. Furthermore, this research also reveals the lack of the advanced PRM tools in the industry for RBIs. They rely mainly upon informal methods provided by their business partners. It is worth noting that these tools, such as a forward contract, are selectively provided to RBIs depending on their relationships and market powers. The accessibility to available PRM tools has a strong linkage to PRM strategies adopted by RBIs. Eventually, adopted PRM strategies incorporated with decisions in risk taking and market channel selection help to determine their business performance. The research concludes by proposing a conceptual model of PRM in practice that is considered to be original and contributes to the industries involved with high-volume and low-margin trading. This research also has implications to novice or existing RBIs, other stakeholders in NR supply chains, such as producers or processors, and policymakers who require more understanding in PRM in practice.
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Baratha, Nesan Krishna Veni. "Phosphorylated Polyurethane film synthesized from Natural Rubber for flame retardant application." Thesis, Le Mans, 2015. http://www.theses.fr/2015LEMA1001.
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L’objectif de ce travail a consisté à développer un revêtement polyuréthane (PU) ignifugeant à partir de caoutchouc naturel. Pour ce faire, deux types de diols ont été utilisés. Un oligoisoprène hydroxytéléchélique a été tout d’abord synthétisé et utilisé comme segment souple. Par ailleurs, un second oligomère phosphorylé, dont les groupements phosphonate ou phosphate sont connus pour offrir des propriétés retardatrices de flamme, et possédant une extrémité diol a été réalisé afin de servir d’extenseur de chaine au cours du procédé one shot d’obtention des revêtements. Ces oligophosphonates ou phosphates ont été obtenus quant à eux selon un procédé de polymérisation radicalaire contrôlé de type RAFT à partir de monomères diethyl (acryloyloxymethyl) phosphonate (DEAMP) et 2-acryloyloxyethyldiethylphosphate (ADEP) afin d'accéder à deux gammes de masses strictes (n~13 and n~21 ) et des dispersités étroites (Ð<1.2). Ces polymères ont été entièrementcaractérisés par RMN 1H, 31P, SEC et spectrométrie Maldi TOF et utilisés en synthèse de polyuréthanes selon deux procédés appelés additif et réactif. Les propriétés physicochimiques et mécaniques des matériaux PU synthétisés ont été comparés à ceux de matériaux PU incorporant selon les mêmes approches une petite molécule phosphorylée, afin de traduire les effets spécifiques de ces oligomères. Les revêtements polyuréthane synthétisés ont été caractérisés par FTIR et spectroscopie Raman afin de mesurer la dispersion des oligomères phosphorés au sein de la matrice polymère. En outre, les propriétés physicochimiques et notamment les propriétés ignifugeante ont été évaluées par TGA, DSC et LOI. En complément, les propriétés mécaniques ont été elles aussi évaluées (élongation à rupture, module, dureté et scratch test). Une étude de mapping par spectroscopie Raman a révélé une meilleure dispersion des additifs dans un matériau obtenu selon l’approche réactive, où l’oligomère phosphorylé est lié de manière covalente au squelette du Polyuréthane. De la même façon, cette dispersion apparaîtplus homogène pour l’utilisation d’un oligomère de chaine plus courte (n=13). Les propriétés ignifugeantes ont été démontrées grâce aux caractérisations TGA et DSC où la première étape de décomposition est retardée quels que soient les pourcentages d’oligomères incorporés à la matrice (1, 5 ou 8%). En outre, il s’avère que les mesures LOI démontrent un maximum proche de 30% pour un pourcentage d’oligomère de 8%, valeur très notablement supérieure à celle de l’additif de comparaison. Concernant les propriétés mécaniques, l’incorporation d’oligomères phosphorylés entraîne une augmentation du module et de la dureté et une diminution de la résistance à l’abrasion. Les valeurs d’élongation à rupture sont cependant très similaires, quelles que soient les formulations testées. Néanmoins, ces propriétés apparaissent très supérieures à celles de la matrice standard, démontrant une plus grande efficacité d’oligomères phosphorylés par comparaison avec une petite molécule de type phosphate ou phosphonate. Ces résultats encourageant laissent entrevoir une perspective d’application industrielle de cette méthodologie vers la production de caoutchoucs ignifugeantsThe aim of this research was to develop polyurethane (PU) coating from Natural Rubber (NR) presenting Flame Retardant (FR) properties. For this purpose, two kinds of diols were used. Hydroxytelechelic oligoisoprenes were firstly synthesized from Natural Rubber (NR) and used as softsegment. Secondly, diol chain end phosphorylated oligophosphonates or oligophosphates were synthesised that would cater as chain extender during the polyurethane synthesis one shot process. Such Phosphorylated oligomer was synthesized by RAFT polymerization of diethyl (acryloyloxymethyl) phosphonate (DEAMP) and 2-acryloyloxyethyl diethylphosphate (ADEP) monomer. A new trithiocarbonate based RAFT agent was synthesized (2-(dihydroxypropan-2-yloxy)carbonyl trithiocarbonate). This RAFT agent was used to polymerize each monomer with welldefinedmolecular weight and narrow dispersities (Đ<1.2). The polymer was well characterised by 1H, 31PNMR, SEC and Maldi TOF. The oligomers were synthesised with two different chain lengths, n≈13 andn≈21 to be used as additive and reactive FR in polyurethane films. As a reference molecule, a phosphatediol was synthesized to be used as a pendent group in polyurethane synthesis.Polyurethane films were fully characterised using FTIR, Raman spectroscopy, TGA, DSC and LOI.The mechanical properties were furthermore evaluated such as elongation at break, modulus, hardnessand scratch test. Polyurethanes with 1, 5, and 8% w/w of the phosphorylated oligomer were preparedaccording two different pathways so called additive or reactive. The main difference consists in thecovalent attachment of the phosphorylated oligomer to the PU backbone in the reactive pathway whilein the additive process, the oligomers are only physically incorporated in the PU. Raman mappingcharacterizations on the different films reveal a better homogeneous distribution of shortphosphorylated oligomer chains using a reactive pathways compared to the additive pathway as well asthe use of longer chains. Moreover TGA Analysis showed lower decomposition temperature on the firststep and an increased decomposition temperature on the second step of all phosphorylated treatedPUs. This indicates char formation from FR oligomer at lower temperature increases the decompositiontemperature on the second step. LOI measurements showed a maximum of 28.2% with shorterphosphate based oligomers added via reactive pathway at 8%w/w ratio.The mechanical properties of PU with phosphorylated oligomer gave similar elongation at breakbetween additive and reactive pathway. Compared to standard PU, the incorporation of the phosphorylated oligomer showed a decrease in scratch resistance and an increase in modulus and hardness. However, these oligomers (additive and reactive) performed better when compared withsmall molecule added as additive fillers. As a perspective, these phosphorylated oligomers on its own,with low Tg values (≈ -30oC), could be used in dry rubber FR application
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Dognani, Guilherme. "Eletrofiação de fibras de borracha natural com adição de polianilina /." Presidente Prudente, 2016. http://hdl.handle.net/11449/134294.
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Orientador: Aldo Eloizo JobCo-orientador: Deuber Lincon da Silva Agostini
Banca: Claudia Merlini
Banca: Neri Alves
O Programa de Pós Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi
Resumo: A técnica de eletrofiação tem sido utilizada na obtenção de fibras com diversos materiais poliméricos. Neste trabalho, foram desenvolvidos, de maneira inédita, materiais eletrofiados a partir de borracha natural e polianilina. Por esta técnica, foram obtidas mantas eletrofiadas com fibras de diâmetro menor que 1 um. Para o desenvolvimento destas mantas eletrofiadas tornou-se necessário primeiramente realizar um amplo estudo sobre os parâmetros de processo, o qual constou em variar o fluxo de vazão da solução polimérica de 0.1, 0,25, 0,5 mL/h, a tensão aplicada ao processo de 10, 12,5....., 15 kV e a rotação do coletor rotativo onde as fibras foram depositadas em 30, 40, 50 rpm. Após o estudo dos parâmetros de eletrofiação, foi selecionada uma série com os melhores parâmetros, que proporcionou a obtenção de mantas de borracha natural denominada BN. Estas mantas foram posteriormente recobertas com polianilina pelo método de polimerização in situ, obtendo mantas de BN/PAni dopada e BN/PAni desdopada. Para fins de comparação foram também produzidas membranas densas pelo método casting, que foram caracterizadas quanto suas propriedades elétricas, onde mostrou bons resultados, se comportando como material ôhmico alcançando a condutividade na ordem de 10-6 S/m para BN/PAni dopada, enquadrado assim entre os materiais semicondutores. Além das propriedades elétricas foram também investigadas as propriedades térmicas, espectroscópicas dos materiais estudados. Os resultados deste trabalho mostraram que é possível eletrofiar a borracha natural formando fibras de diâmetro que alcançaram valores mínimos de até 0,92 um
Abstract: The electrospinning technique has been used to obtain fibers with various polymer materials. In this work were developed in an unprecedented fibers electrospun from natural rubber and polyaniline. For this technique, fibers mats were obtained with fiber diameter of less than 1 micrometers. For the development of these electrospun mats became necessary to first perform an extensive study on the process parameters, which consisted in varying the flow of polymer solution at 0.1, 0.25, 0.5 ml/h, the voltage applied to the process 10, 12.5, 15 kV and rotation of the collector where the fibers were deposited on 30, 40, 50 rpm. After studying the electrospinning parameters, it selected a series with the best parameters, which provided obtaining natural rubber mats called NR. These mats were covered with polyaniline by in situ polymerization method, getting NR/PAni doped and NR/PAni undoped mats. For purposes of comparison were also produced membranes by casting method, which were characterized as its electrical properties, which showed good results, behaving as ohmic materials reaching the conductivity on the order of 10-6 S/m for NR/PAni doped, entering among the semiconductor materials. In addition to the electrical properties were also investigated the thermal, spectroscopic and morphological materials properties. These results showed that it is possible produced natural rubber fibers electrospun forming diameter fibers that have reached minimum values of up to 0.92 micrometers
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Fernandes, Marcos Gonzales. "Obtenção de nanocompósitos de borracha natural e organoargila com variação no processo de organofilização." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-07112017-145922/.
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Foi preparado o nanocompósito de borracha natural/argila chocolate B modificada por sodificação via seca com variação no processo, utilizando silicato de sódio ao invés de carbonato de sódio e tratada com sal quaternário de amônio, cloreto hexadecil trimetil amônio. A argila no seu estado natural, após sodificação e após quaternização foi caracterizada pelas técnicas de microscopia estereoscópica, análise térmica, infravermelho, difração de raios X e microscopia eletrônica de varredura. Outras cargas orgânicas foram adicionadas, como celulose e piaçava e comparadas com cargas tradicionais, como o negro de fumo. As placas obtidas, após vulcanização, tiveram medidas as suas propriedades mecânicas e foram analisadas por DRX e MEV. Os nanocompósitos obtidos mostraram melhoria nas suas propriedades mecânicas em comparação com as placas sem a adição de argila.The natural rubber/clay chocolate B nanocomposite modified by dry sodification process with variation processing was prepared using sodium silicate instead of sodium carbonate and treated with quaternary ammonium salt, hexadecyl trimethyl ammonium chloride. The clay in its natural state after sodification and after quaternization was characterized by the techniques of stereoscopic microscopy, thermal analysis, infrared, X-ray diffraction and scanning electron microscopy. Other organic fillers were added, such as cellulose and piaçava, and compared with traditional fillers such as carbon black. The plates obtained after vulcanization had their mechanical properties measured and were analyzed by XRD and SEM. The obtained nanocomposites showed improvement in their mechanical properties in comparison with the plates without the addition of clay.
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Sanches, Alex Otávio [UNESP]. "Obtenção e caracterização elétrica e morfológica de compósitos de borracha natural com PZT." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/91967.
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Compósitos de borracha natural vulcanizada (BV) e Titanato Zirconato de Chumbo (PZT) em diferentes composições foram obtidos a partir do látex pré-vulcanizado e da cerâmica PZT na forma de pó. As composições estudadas foram 90/10, 80/20, 70/30 e 60/40 v/v. Um aumento no coeficiente piezoelétrico (d33) foi verificado com o aumento do volume de cerâmica no compósito, atingindo um valor de aproximadamente 6 pC/N para compósitos de composição 60/40 polarizados a 8MV/m na temperatura de 90°C. Verificou-se um decaimento da atividade piezoelétrica em função do tempo após a polarização para os compósitos com até 30% em volume de cerâmica. Este decaimento foi atribuído principalmente à relaxação da matriz. A adição de nanofibras de celulose para a composição 70/30 nas proporções 5,10 e 15% em massa (em relação à massa da borracha), inibiu o processo de relaxação, como também promoveu uma melhor transferência de tensões mecânicas aplicadas no material aos grãos cerâmicos, ocasionando em um aumento de até 400% nos valores obtidos para o coeficiente piezoelétrico. A incorporação de 5% em massa de nanofibras recobertas com polianilina aumentou três ordens de grandeza a condutividade elétrica dos compósitos 70/30 e 60/40. Por outro lado, uma redução nos valores do coeficiente piezoelétrico foi observada, o que foi atribuído a um efeito de blindagem elétrica dos grãos cerâmicos
Vulcanized natural rubber(VNR) and Lead Zirconate Titanate (PZT) composites with different composition were obtained by mixing PZT ceramic powder with prevulcanized latex. The investigated composition of VNR/PZT were 90/10, 80/20, 70/30 and 60/40 v/v. The piezoelectric coefficient d33 increased with increasing of PZT volume fraction in the composite reaching approximately 6 pC/N for composites composition 60/40 %v/v, polarized with 8MV/m at 900C. It was verified that piezoelectric activity decay as a function of time for composite up to 30% of ceramic, that was attributed mainly to matrix relaxation. The incorporation of cellulose nanofibers in the compositions 70/30 and 60/40 %v/v inhibited the matrix relaxation besides of promoting better transference of the applied mechanical stress on the ceramic grains, increasing the piezoelectric coefficient d33 about 400%. The electrical conductivity of composites 70/30 and 60/40 increased three order of magnitude by adding 5% in mass (related to rubber mass), of cellulose nanofiber coated with polyaniline in the composite. On the another hand, the piezoelectricity activity d33 decreased and this behavior was attributed to electrical field shielding of ceramic grain promoted by coated fibers
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Sanches, Alex Otávio. "Obtenção e caracterização elétrica e morfológica de compósitos de borracha natural com PZT /." Ilha Solteira, 2012. http://hdl.handle.net/11449/91967.
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Orientador: José Antonio MalmongeBanca: Walter Katsumi Sakamoto
Banca: Neri Alves
Resumo: Compósitos de borracha natural vulcanizada (BV) e Titanato Zirconato de Chumbo (PZT) em diferentes composições foram obtidos a partir do látex pré-vulcanizado e da cerâmica PZT na forma de pó. As composições estudadas foram 90/10, 80/20, 70/30 e 60/40 v/v. Um aumento no coeficiente piezoelétrico (d33) foi verificado com o aumento do volume de cerâmica no compósito, atingindo um valor de aproximadamente 6 pC/N para compósitos de composição 60/40 polarizados a 8MV/m na temperatura de 90°C. Verificou-se um decaimento da atividade piezoelétrica em função do tempo após a polarização para os compósitos com até 30% em volume de cerâmica. Este decaimento foi atribuído principalmente à relaxação da matriz. A adição de nanofibras de celulose para a composição 70/30 nas proporções 5,10 e 15% em massa (em relação à massa da borracha), inibiu o processo de relaxação, como também promoveu uma melhor transferência de tensões mecânicas aplicadas no material aos grãos cerâmicos, ocasionando em um aumento de até 400% nos valores obtidos para o coeficiente piezoelétrico. A incorporação de 5% em massa de nanofibras recobertas com polianilina aumentou três ordens de grandeza a condutividade elétrica dos compósitos 70/30 e 60/40. Por outro lado, uma redução nos valores do coeficiente piezoelétrico foi observada, o que foi atribuído a um efeito de blindagem elétrica dos grãos cerâmicos
Abstract: Vulcanized natural rubber(VNR) and Lead Zirconate Titanate (PZT) composites with different composition were obtained by mixing PZT ceramic powder with prevulcanized latex. The investigated composition of VNR/PZT were 90/10, 80/20, 70/30 and 60/40 v/v. The piezoelectric coefficient d33 increased with increasing of PZT volume fraction in the composite reaching approximately 6 pC/N for composites composition 60/40 %v/v, polarized with 8MV/m at 900C. It was verified that piezoelectric activity decay as a function of time for composite up to 30% of ceramic, that was attributed mainly to matrix relaxation. The incorporation of cellulose nanofibers in the compositions 70/30 and 60/40 %v/v inhibited the matrix relaxation besides of promoting better transference of the applied mechanical stress on the ceramic grains, increasing the piezoelectric coefficient d33 about 400%. The electrical conductivity of composites 70/30 and 60/40 increased three order of magnitude by adding 5% in mass (related to rubber mass), of cellulose nanofiber coated with polyaniline in the composite. On the another hand, the piezoelectricity activity d33 decreased and this behavior was attributed to electrical field shielding of ceramic grain promoted by coated fibers
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Rooj, Sandip. "Reinforcement of Natural Rubber by “Expanded Clay” Adopting “Propping-Open Approach”." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-129370.
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During the last years rubber nanocomposites obtained by incorporating anisotropic clay nanoparticles within a rubber matrix to tailor material properties have attracted steadily growing interest. However, one main complication preventing rubber-clay nanocomposites from many potential applications is the difficulty to achieve a high degree of exfoliation particularly in case of melt mixing or compounding (using mixing equipment like internal mixer, two roll mills which can be up-scaled in industry). Albeit commercially available organomodified montmorillonite clays (OMt) are fairly compatible with the polar rubber like Acrylo-nitrile butadiene rubber (NBR), carboxylated nitrile rubber (XNBR), chloroprene rubber (CR) etc., its dispersion in non-polar rubbers like natural rubber (NR), is rather unsatisfactory. Incorporation of only 5 phr of OMt in NR by mechanical mixing leads to very poor dispersions with larger aggregates. Large agglomerates of OMt were observed with bare eyes throughout the matrix. Even in the TEM micrographs, highly agglomerated structures of clay particle were observed. A high degree of exfoliation of such clay is achieved in NR utilizing the so called ‘Propping-open approach’ where stepwise expansion of interlayer spacing of Mt took place. A series of long chain fatty acids (C16-C22) are intercalated into the interlayer space of OMt and a gradual expansion of the interlayer space were observed as the chain length of the fatty acid increased. Wide angle X-ray diffraction (WAXD), Fourier transform infrared spectroscopy (FTIR) and contact angle measurement indicated successful intercalation of the fatty acids into the interlayer space of the clay minerals. Since the fatty acid containing 22 carbon atoms has the largest interlayer distance among the modified samples studied, it has been selected for further study to understand the reinforcing behavior in NR matrix. An unusual mechanical percolation behavior of EOMt nanoparticles was observed in a NR matrix. The value of the mechanical percolation threshold (φp) and the fractal nature of nanoparticle clusters were determined through an analysis of the experimental data based on a theory put forward by Huber and Vilgis. This phenomenon was discussed in terms of fractal dimensions of the nanoparticle cluster. The impact of filler dispersion and rubber-filler interactions on the viscoelastic behavior of NR nanocomposites was systematically investigated. Significant non-linear viscoelastic behavior (Payne effect) was observed at very low EOMt content. Kraus and Maier-Göritz models were utilized to interpret such non-linear viscoelastic behavior. The nanocomposites showed enormous improvement in different physic-mechanical properties in the presence of EOMt. Technical elastomers are generally filled with certain fillers (e.g. carbon black) in order to reinforce the rubber matrix for some typical applications like tires, conveyer belts etc. Such rubber goods are always exposed to cyclic stress and deformations attributed to their dynamic application. Under constant and repeated applied stress, cracks develop at a stress concentration point, which could lead to ultimate failure. Therefore, the crack initiation and propagation behavior in such rubber products is very fundamental and need proper attention. The role of EOMt nanoparticles on the microstructure and fracture mechanical behavior of CB filled NR composites was investigated. Using pure-shear test specimen tear fatigue analysis (TFA) tests under cyclic conditions were carried out to explicate the crack growth behavior of CB filled NR in the presence of EOMt. A significant reduction in crack growth rate was noticed in the presence of only 5 phr of EOMt. Furthermore, instrumented tensile-impact tests (IT-IT) were also performed for the characterization of the crack resistance of the materials under impact-like loading conditionsDie Einarbeitung von nur 5 phr organisch modifizierten Montmorillonite (OMt) in Naturkautschuk (NR) durch mechanisches Mischen führt zu einer sehr schlechten Verteilung mit größeren Aggregaten. Große Agglomerate von OMt waren mit bloßem Auge in der NR Matrix sichtbar. Sogar in TEM Aufnahmen wurden stark agglomerierte Strukturen beobachtet. Ein hoher Grad der Exfolierung von diesem Clay in NR wird durch die Nutzung des so genannten ‘Propping-open’ Ansatzes erreicht, in dem eine stufenweise Aufweitung des Zwischenschichtabstandes des OMt stattfindet. Eine Reihe langkettiger Fettsäuren (C16 – C22) wurde in die Zwischenschicht des OMt eingefügt. Mit zunehmender Kettenlänge der Fettsäuren wurde eine allmähliche Aufweitung der Zwischenschicht beobachtet. Da OMt, der mit einer Fettsäure mit 22 Kohlenstoffatomen modifiziert wurde, den größten Zwischenschichtabstand aller untersuchten Proben hatte, wurde diese Fettsäure für die weiteren Untersuchungen ausgewählt, um das Verstärkungsverhalten in der NR Matrix zu verstehen. Ein ungewöhliches Perkolationsverhalten der expandierten OMt (EOMt) Nanopartikel wurde in einer NR Matrix beobachtet. Der Wert der mechanischen Perkolationsschwelle (φp) und die fraktale Natur der Nanopartikel Cluster wurden durch eine Analyse der experimentellen Daten bestimmt, wobei eine Theorie, die von Huber und Vilgis vorangetrieben wurde, zur Anwendung kam. Dieses Phänomen wurde in Bezug auf die fraktalen Dimensionen der Nanopartikel Cluster diskutiert. Die Einfluss von EOMt Nanopartikel auf die Mikrostruktur und das mechanische Bruchverhalten von russgefüllten NR Kompositen wurde untersucht. Unter Verwendung reiner Schertestproben wurden Rissermüdungsanalysen unter zyklischer Belastung ausgeführt, um das Risswachstumsverhalten von russgefülltem NR in der Gegenwart von EOMt zu untersuchen und zu erklären. Eine signifikante Reduktion der Rissausbreitungsrate wurde in Gegenwart von nur 5 phr EOMt erreicht. Des Weiteren wurden auch instrumentierte Schlagzugprüfungen zur Charakterisierung des Risswiderstandes von Materialien unter schlagartigen Belastungsbedingungen durchgeführt
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Gushterov, Nikola [Verfasser]. "Thermodynamic and Mechanical Characterization of Shape-Memory Natural Rubber / Nikola Gushterov." München : Verlag Dr. Hut, 2017. http://d-nb.info/1137024518/34.
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