A series of particulate reinforced natural rubber composites are prepared using both model (glass sphere) and commercial (carbon black and precipitated silica) reinforcing filler materials having a range of surface activities. Small strain reinforcement and viscoelastic behaviour of the model (glass sphere-filled) microcomposites are found to be well described by hydrodynamics and temperature-insensitive stiffening mechanisms such as strain amplification and elastomer occlusion. This means that the energy applied to the model materials during small strain deformations is entirely stored and dissipated within the elastomer phase. For carbon black-filled natural rubbers such mechanisms are no longer found to completely describe the levels of reinforcement and viscoelastic behaviour. This is the case particularly for high surface area carbon blacks of small aggregate size. For carbon blacks, additional mechanisms of reinforcement are identified and associated with the formation of a filler network and with effects at the polymer-filler interface. For all the compounds considered in this study, no direct experimental evidence is found for the formation of significant volumes of interphase polymer exhibiting retarded chain dynamics near the filler surface. The observation of a secondary dissipation process in rubbery region small strain dynamic mechanical and creep measurements of carbon black-natural rubber compounds where the polymer filler interaction is particularly poor (where the carbon black surface is graphitised) indicates that there may be a significant slippage of polymer chain segments at the filler-elastomer interface. There is some limited evidence from small strain creep testing to indicate that this process also occurs in commercial carbon black-filled compounds but to a much reduced extent. To the best of the author's knowledge this is the first time that such processes have been observed in carbon black filled elastomers.

This study aims to understand the behaviour of a novel elastomer where hollow microspheres are used as a particulate filler. The behaviour of elastomers filled with rigid particles, is fairly well understood, where the stiffness increases as the amount of filler material is increased, alternatively, foamed elastomers which are usually produced with either closed cells or open cells, have been shown to become softer as the volume of the voids are increased. When traditional foam materials are compressed they exhibit non-linear behaviour in three distinct phases, the cell walls firstly bend, then they buckle and this is followed by densification. To understand the overall physical behaviour of the material, tensile tests of the elastomer material were conducted using unfilled materials and filled with a range of the hollow sphere filler volume fractions. Compression tests were also conducted on small cylinders, again using unfilled and filled rubbers with a range of filler volume fractions. The physical tests showed that increasing the filler volume fraction increased the reinforcing effect at low strains with an associated increase in stiffness, but the material then became increasingly less stiff at higher strains. To understand the behaviour of the bulk material, the mechanical behaviour of single hollow spheres under strain were investigated, both as a standalone material and then also embedded in an elastomer. To examine the mechanical behaviour of a single hollow plastic sphere a single microsphere was compressed using nano-indentation, the tests were then replicated at a larger scale using model table tennis balls. FEA software was used to model the behaviour of both types of hollow sphere, as well as a wide range of other spheres to better understand their buckling behaviour, to help predict the behaviour of microspheres with different ratios of wall thickness to diameters. To examine the behaviour of hollow spheres in a rubber matrix, simple cylindrical unit cells were made with a single hollow plastic sphere embedded within them. These model cylinders were produced with a translucent elastomer containing a single table tennis ball. Their behaviour in compression and in tension and that of a single hollow plastic sphere embedded in an elastomer was also modelled using FEA software, the effects of debonding and buckling were determined for small and large strains and were used to examine the more complex behaviour of the filled composite. A comparison between the measured behaviour and the various models indicates that the bulk behaviour of the microsphere filled elastomers is primarily determined by a progressive dewetting process of the rubber away from the microsphere in tension and by buckling phenomena of the hollow spheres in compression.

Orientador: Aldo Eloizo Job / Banca: Ricardo Flávio Aroca / Banca: Valtencir Zucolotto / O Programa de Pós Graduação em Ciência e Tecnologia de Materiais, PosMat, tem carater institucional e integra as atividades de pesquisa em materiais de diversos campi / Resumo: Neste trabalho, desenvolvido junto ao Grupo de Pesquisa em Novos Materiais e Aplicações, do Departamento de Física, Química e Biologia, da Faculdade de Ciência e Tecnologia FCT/UNESP Campus de Presidente Prudente, propomos realizar a investigação da fabricação de membranas de borracha a partir do látex extraído de árvores do gênero Hevea brasiliensis (clone RRIM 600 - Rubber Research Institute of Malaysia). As membranas são preparadas através da técnica de casting e utilizadas como substratos ativos (agente redutor e estabilizador) nas sínteses de nanopartículas (NPs) metálicas, pelo método de redução in situ, por meio de solução aquosa de cloreto de ouro (AuCl3), de modo que as nanopartículas sejam incorporadas tanto na superfície quanto no volume das membranas. Como objetivo principal propõe-se obter informações relevantes sobre os compostos ligados às membranas de borracha natural aos quais se atribuí a responsabilidade pela redução e estabilização das nanopartículas. Os resultados demonstram que a síntese de nanopartículas pode ser desenvolvida, com tamanhos médios por volta de 48 nm, incorporando-as como agregados na superfície das membranas de borracha natural. A redução das nanopartículas de ouro foi atribuída principalmente a componentes protéicos presentes na Fase Soro do látex. Os compósitos obtidos apresentam boa estabilidade térmica e foram utilizados, como aplicação, na construção de substratos flexíveis para a análise química por meio de espectroscopia micro-Raman analisando o efeito Surface Enhanced Raman Spectroscopy (SERS) e Surface Enhanced Ressonance Raman Spectroscopy (SERRS) e Surface Enhanced Ressonance Raman Spectroscopy (SERRS) / Abstract: In this work, developed together the Research Group of New Materials and Applications, Department of Physics, Chemistry and Biology from Faculty of Science and Technology FCT/UNESP in Presidente Prudente, proposes to conduct research the manufacture of rubber membranes from natural latex extracted from trees from Hevea brasiliensis (clone RRIM 600 - Rubber Research Institute of Malaysia). This membranes were prepared by casting technique and used as active substrates (both reducing and stabilizer agent) in the synthesis of metal nanoparticles (NPs) by in situ reduction method, using gold chloride (AuCl3) aqueous solution, so that the nanoparticles are incorporated both on surface and embebbed into the membrances. The main objective is obtaining relevant information on the compounds of the natural rubber membrances which assigns responsability for the reduction and stabilization of nanoparticles. The results obtained demonstrate that the synthesis of nanoparticles achieved, with average sizes around 48 nm, incorporated on the surface of natural rubber membranes. The reduction of gold nanoparticles is attributed mainly to the protein components present in the serum phase of the latex. The composites showing good thermal stability and were used, as application, in the construction of flexible substrate for chemical analysis using micro-Raman spectroscopy evaluated the Surface Raman Spectroscopy (SERS) and Surface Enhanced Ressonance Raman Spectroscopy (SERRS) effects / Mestre

<i>Hevea brasiliensis </i>latex contains a large quantity of high molecular weight rubber and is thus the primary commercial source of natural rubber. Rubber and other non-rubber isoprenoids in <i>Hevea </i>latex are synthesised from isopentenyl diphosphate (IPP) generated from the cytoplasmic mevalonate (MVA) pathway and the plastidic methyl erythritol phosphate pathway (MEP). This study utilised two rubber tree clones (RRIM600 and PB235) that show visibly contrasting levels of yellow carotenoids for the measurement of latex isoprenoids (carotenoids, rubber and isoprenoid intermediates) and transcript levels of the genes involved in isoprenoid biosynthesis. Metabolite extraction and analysis showed that four major carotenoids namely lutein, zeaxanthin, α-carotene and β-carotene were consistently present in both RRIM600 and PB235 latex. β-carotene was found to be the major carotenoid, at 1.2 μg/g in PB235 and 0.8 μg/g in RRIM600 fresh latex samples. However, the analytical method developed to measure isoprenoid intermediates needed to be further optimised to increase extraction efficiency. To enable accurate measurement of transcript levels of key genes involved in the isoprenoid biosynthetic pathway, a set of reference transcripts was constructed by merging short-reads (RNA-seq) and long-reads (Iso-seq and full-length cDNA sequences) data from <i>Hevea brasiliensis</i>. This produced a comprehensive set of 193,997 transcript sequences with good level of coverage of predicted transcripts and highly conserved core plant genes. Not only did the reference transcriptome update the annotation of rubber gene models, additional transcript variants were also discovered. Manual curation of gene models for key steps associated with rubber and carotenoids resulted in a repertoire of 115 genes, with 151 corresponding transcript variants. Subsequently, differential expression analysis on the basis of mapping RRIM600 and PB235 RNA-seq reads to the reference transcriptome revealed isoform-specific expression of genes for biosynthesis of carotenoids (PSY isoform 2), IPP (AACT2 and HMGR1) and rubber (REFSRPP gene members). In addition, the levels of these genes correlated positively with the carotenoid and rubber content measurements from the same latex of PB235 and RRIM600 used for metabolite extraction. Finally, the utility of the reference transcript catalogue was demonstrated by the characterisation of the REFSRPP gene family, which is involved in rubber elongation steps. REFSRPP gene family showed a local expansion which appear to be unique to <i>Hevea</i>. A pilot study has demonstrated there is considerable diversity of the genomic region containing the duplicated REFSRPP genes.

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.

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.

Dissertation (Ph. D.)--University of Akron, Dept. of Polymer Science, 2009. / "May, 2009." Title from electronic dissertation title page (viewed 11/29/2009) Advisor, Judit E. Puskas; Committee members, Roderic P. Quirk, Joseph P. Kennedy, Li Jia, Chrys Wesdemiotis; Department Chair, Ali Dhinojwala; Dean of the College, Stephen Z. D. Cheng; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.

Ionomers bearing reactive ion-pair functionality are a novel class of materials that have been prepared. The N-alkylation of N-vinylimidazole by poly(isobutylene-co-isoprene) produced the reactive ionomer product in good yield, through a solvent-borne process. Solvent-free conditions can also be used to produce reactive ionomers by the N-alkylation of N-vinylimidazole by poly(isobutylene-co-para-methylstyrene). Characterization of these derivatives was carried out with the assistance of model compounds, and showed excellent agreement with 1H NMR spectra. These reactive ionomers readily crosslink with peroxide at elevated temperatures and in the absence of peroxide they have excellent thermal stability. The amount of crosslinking can be altered based on the vinyl content of the material, to target various applications. N-alkylation of N-vinylimidazole can be carried out concurrently with a non-reactive N-alkylimidazole to achieve desired vinyl contents and tailor the physical properties of these materials. These materials contain both ionic and covalent crosslink networks, and this hybrid network structure provides these materials with unique crosslink structures and stress relaxation properties. Conventional rubber fillers are compatible with these novel reactive ionomers. Carbon black and precipitated silica have no adverse effects on the peroxide crosslinking of the elastomers and a constant peroxide loading can be used regardless of the filler loading. Payne analysis shows good filler dispersion at low filler loading; however, there is some evidence of reticulate filler network formation at high filler loadings. / Thesis (Master, Chemical Engineering) -- Queen's University, 2012-03-31 21:12:46.618

Asphalt-rubber mixtures have been shown to have useful properties with respect to distresses observed in asphalt concrete pavements. The most notable change in properties is a large increase in viscosity and improved low-temperature cracking resistance. Warm mix additives can lower production and compaction temperatures. Lower temperatures reduce harmful emissions and lower energy consumption, and thus provide environmental benefits and cut costs. In this study, the effects of crumb rubber modification on various asphalts such as California Valley, Boscan, Alaska North Slope, Laguna and Cold Lake were also studied. The materials used for warm mix modification were obtained from various commercial sources. The RAF binder was produced by Imperial Oil in their Nanticoke, Ontario, refinery on Lake Erie. A second commercial PG 52-34 (hereafter denoted as NER) was obtained/sampled during the construction of a northern Ontario MTO contract. Some regular tests such as Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR), Multiple Stress Creep Recovery (MSCR) and some modified new protocols such as the extended BBR test (LS-308) and the Double-Edge Notched Tension (DENT) test (LS-299) are used to study, the effect of warm mix and a host of other additives on rheological, aging and failure properties. A comparison in the properties of RAF and NER asphalts has also been made as RAF is good quality asphalt and NER is bad quality asphalt. From the studies the effect of additives on chemical and physical hardening tendencies was found to be significant. The asphalt samples tested in this study showed a range of tendencies for chemical and physical hardening. / Thesis (Master, Chemistry) -- Queen's University, 2014-01-30 11:56:43.978

The degree of carbon black dispersion is a very important consideration in the manufacture of rubber both in quality control and basic research. A study has been made of various aspects of assessing dispersion and the dispersion process of carbon black in rubber. The main objectives of this work were: (1) To investigate the relationship between the light scattered at a fixed angle from the rubber surface and carbon black dispersion and hence develop and evaluate a new dispersion assessment system. (2) To determine the normal variations of industrial rubber mixing installations, and (3) To study the effect of internal mixing variables on black dispersion and other properties of rubber. To achieve these goals a carbon black dispersion assessment system based on an inverted Dark Field Reflected Light (D.F.R.L.) microscope was developed in three versions and successfully tested. The three versions differed in their degree of sophistication and automation and would be expected to find application ranging from routine quality control to research. The basic principle was that a rubber sample (cured or uncured) was cut with a new razor blade and the surface observed in a D.F.R.L. microscope. The light beam from the sample surface is sensed by a photometer and its intensity was shown to be related to black dispersion. In version III an automatic stage driven by two stepper motors was designed and fitted to the microscope to perform object plane scanning. The photometer and the stage were interfaced with an Apple II microcomputer providing the following functions; stage control, photometer control, data acquisition, statistical analysis, data storage and results output. The system was evaluated by taking measurements on several identically formulated compounds differing only in black dispersion. A general rubber goods and a tyre manufacturing installation were studied. Several production batches were sampled at various mixing stages and subjected to black dispersion assessment, cure and vulcanisate properties measurement. Analysis of variance of the results was accomplished with a statistical computer package designated GENSTAT Version 4.03. Factorial experimental designs and multivariate regression analysis techniques were used in studying the effect of mixing variables on black dispersion and other properties. The results are presented in the form of response equations and contour graphs are used to enable second order interactions to be readily identified.