Showing papers on "Natural rubber published in 2000"
TL;DR: In this paper, the surface modification of powdered tire rubber to increase its adhesion to cement paste was studied and the results of fracture energy and flexural and compressive strength showed that the addition of rubber particles improves the toughness and reduces the porosity of the specimens.
511 citations
TL;DR: A complementary approach to guayule with yeast species is set up, which may more quickly show the applicability and relevance of genes selected and the risk of crop failure, diminishing acreage, and other disadvantages outlined below.
Abstract: Rubber (cis-1,4-polyisoprene) is one of the most important polymers naturally produced by plants because it is a strategic raw material used in more than 40,000 products, including more than 400 medical devices. The sole commercial source, at present, is natural rubber harvested from the Brazilian rubber tree, Hevea brasiliensis. Primarily due to its molecular structure and high molecular weight (>1 million daltons) this rubber has high performance properties that cannot easily be mimicked by artificially produced polymers, such as those derived from, e.g., bacterial poly-hydroxy-alkanoates (PHAs). These high performance properties include resilience, elasticity, abrasion resistance, efficient heat dispersion (minimizing heat build-up under friction), and impact resistance. Medical rubber gloves need to fit well, be break-resistant, allow the wearer to retain fine tactile sensation, and provide an effective barrier against pathogens. The sum of all these characteristics cannot yet be achieved using synthetic gloves. The lack of biodiversity in natural rubber production renders continuity of supply insecure, because of the risk of crop failure, diminishing acreage, and other disadvantages outlined below. A search for alternative sources of natural rubber production has already resulted in a large number of interesting plants and prospects for immediate industrial exploitation of guayule (Parthenium argentatum) as a source of high quality latex. Metabolic engineering will permit the production of new crops designed to accumulate new types of valued isoprenoid metabolites, such as rubber and carotenoids, and new combinations extractable from the same crop. Currently, experiments are underway to genetically improve guayule rubber production strains in both quantitative and qualitative respects. Since the choice for gene activities to be introduced or changed is under debate, we have set up a complementary approach to guayule with yeast species, which may more quickly show the applicability and relevance of genes selected. Although economic considerations may prevent commercial exploitation of new rubber-producing microorganisms, transgenic yeasts and bacteria may yield intermediate or alternative (poly-)isoprenes suitable for specific applications.
308 citations
02 Nov 2000
TL;DR: Guayule rubber Hevea natural rubber modified natural rubber chemical modification of synthetic elastomers liquid rubber powdered rubber rubber rubber-rubber blends - part 1 rubber-Rubber blends as mentioned in this paper.
Abstract: Guayule rubber Hevea natural rubber modified natural rubber chemical modification of synthetic elastomers liquid rubber powdered rubber rubber-rubber blends - part 1 rubber-rubber blends - part 2, new developments short fibre-filled rubber composites thermoplastic styrenic block copolymers polyester thermoplastic elastomers - part 1 polyester thermoplastic elastomers - part thermoplastic polyurethane elastomers thermoplastic polyamide elastomers ionomeric thermoplastic elastomers miscellaneous thermoplastic elastomers halogen containing elastomer tetrafluoro ethylene-propylene rubber carboxylated rubber polyphosphazene elastomers advances in silicon rubber technology - part 1, 1944-1986 advances in silicon rubber technology - part 2, current trends acrylic-based elastomer poly(propylene oxide) elastomer polyalkenylenes polytetrahydrofuran crosslinked polyethylene millable polyurethane elastomers cast polyurethane elastomers polynorbornene rubber nitrile and hydrogenated nitrile rubber diene-based elastomer recycling rubber EPDM rubber technology isobutylene-based elastomers.
304 citations
TL;DR: In this paper, the main structure of the dispersion of clay in the SBR was a layer bundle whose thickness was 4-10 nm and its aggregation formed by several or many layer bundles.
Abstract: Based on the character of a clay that could be separated into many 1-nm thickness monolayers, clay styrene-butadiene rubber (SBR) nanocomposites were acquired by mixing the SBR latex with a clay/water dispersion and coagulating the mixture. The structure of the dispersion of clay in the SBR was studied through TEM. The mechanical properties of clay/SBR nanocomposites with different filling amounts of clay were studied. The results showed that the main structure of the dispersion of clay in the SBR was a layer bundle whose thickness was 4–10 nm and its aggregation formed by several or many layer bundles. Compared with the other filler, some mechanical properties of clay/SBR nanocomposites exceeded those of carbon black/SBR composites and they were higher than those of clay/SBR composites produced by directly mixing clay with SBR through regular rubber processing means. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1873–1878, 2000
276 citations
Patent•
20 Mar 2000
TL;DR: In this paper, a multilayer golf ball consisting of a core, an inner cover layer and an outer cover layer was constructed using a thermoset material having a second shore D hardness less than the first.
Abstract: The present invention is directed towards a method of forming a multilayer golf ball which comprises a core, an inner cover layer and an outer cover layer. The steps include forming a golf ball core; molding an inner cover layer around said golf ball core with a material having a first shore D hardness; and casting an outer cover layer around said inner cover layer and golf ball core with a thermoset material having a second shore D hardness less than the first. The core is comprised of a center made from a first rubber based material and an outer layer formed from a second rubber based material. Preferably, the first rubber based material has about 15 to 25 parts of a crosslinking agent per hundred parts of rubber and the second rubber based material has about 20 to 40 parts of a crosslinking agent per hundred parts of rubber.
261 citations
TL;DR: In this paper, the effect of filler particles such as carbon black on the time-dependent, hysteretic stress-strain behavior of elastomers was investigated and a constitutive model for the behavior was decomposed into an equilibrium molecular network acting in parallel with a ratedependent network.
261 citations
TL;DR: In this paper, simultaneous measurements of the stress-strain behavior and X-ray scattering intensity of vulcanized natural rubber were made continuously by a specially designed instrument during elongation and subsequent retraction.
246 citations
TL;DR: In this paper, a theoretical concept of rubber friction on rough surfaces is presented that relates the frictional force to the dissipated energy of the rubber during sliding stochastic excitations on a broad frequency scale.
Abstract: A basic theoretical concept of rubber friction on rough surfaces is presented that relates the frictional force to the dissipated energy of the rubber during sliding stochastic excitations on a broad frequency scale. It is shown that this is of high relevance for tire traction and allows for a prediction of the likely level of friction of tread compounds on the basis of viscoelastic data. The impact of both, the frequency dependent loss- and storage modulus on the frictional force during sliding of tires on rough tracks, is demonstrated quantitatively for different sliding velocities. The effect of the surface roughness of road tracks is described by three characteristic surface descriptors, i.e., the fractal dimension and the correlation lengths parallel and normal to the surface. These descriptors can be obtained from a fractal analysis of the road texture via stylus- or laser measurements. In particular, it is shown that the applied model of rubber friction is in agreement with the classical f...
227 citations
TL;DR: Rubber-clay nanocomposites were prepared by two different methods and characterized with TEM and XRD as discussed by the authors, which showed that the clay layer could be uniformly dispersed in the rubber matrix on the nanometer level.
Abstract: Rubber–clay nanocomposites were prepared by two different methods and characterized with TEM and XRD. The TEM showed clay had been dispersed to one or several layers. The XRD showed that the basal spacing in the clay was increased. It was evident that some macromolecules intercalated to the clay layer galleries. The clay layer could be uniformly dispersed in the rubber matrix on the nanometer level. The mechanical tests showed that the nanocomposites had good mechanical properties. Some properties exceeded those of rubber reinforced with carbon black, so the clay layers could be used as an important reinforcing agent as the carbon black was. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1879–1883, 2000
220 citations
TL;DR: In this paper, the authors investigated the shear modulus and damping ratio of granulated rubber/sand mixtures using a torsional resonant column and found that 50% granulated tire rubber is close to a typical saturated cohesive soil.
Abstract: Processed waste tires mixed with soils are applicable in lightweight fills for slopes, retaining walls, and embankments that may be subjected to seismic loads. Rubber's high damping capacity permits consideration of granulated rubber/soil mixtures as part of a damping system to reduce vibration. The dynamic properties of granulated rubber/soil mixtures are essential for the design of such systems. This research investigates the shear modulus and damping ratio of granulated rubber/sand mixtures using a torsional resonant column. Specimens were constructed using different percentages of granulated tire rubber and Ottawa sand at several different percentages. The maximum shear modulus and minimum damping ratio are presented with the percentage of granulated rubber. It is shown that reference strain can be used to normalize the shear modulus into a less scattered band for granulated rubber/sand mixtures. The normalized shear modulus reduction for 50% granulated rubber (by volumme) is close to a typical saturated cohesive soil. Empirical estimation of maximum shear modulus of soil/rubber mixtures can be achieved by treating the volume of rubber as voids.
203 citations
TL;DR: In this article, Hevea brasiliensis seed oil was extracted, and its physical and chemical characteristics determined, and the results supported the choice of monosters, in place of straight rubber seed oil, as having better potential for use as alternative diesel fuel.
TL;DR: Spectra demonstrated the decrease in number ofcis-1,4 double bonds, the formation of carbonyl groups, and the change of the overall chemical environment, indicating that an oxidative attack at the double bond is the first metabolic step of the biodegradation process.
Abstract: Several actinomycetes isolated from nature were able to use both natural rubber (NR) and synthetic cis-1,4-polyisoprene rubber (IR) as a sole source of carbon. According to their degradation behavior, they were divided into two groups. Representatives of the first group grew only in direct contact to the rubber substrate and led to considerable disintegration of the material during cultivation. The second group consisted of weaker rubber decomposers that did not grow adhesively, as indicated by the formation of clear zones (translucent halos) around bacterial colonies after cultivation on NR dispersed in mineral agar. Taxonomic analysis of four selected strains based on 16S rRNA similarity examinations revealed two Gordonia sp. strains, VH2 and Kb2, and one Mycobacterium fortuitum strain, NF4, belonging to the first group as well as one Micromonospora aurantiaca strain, W2b, belonging to the second group. Schiff's reagent staining tests performed for each of the strains indicated colonization of the rubber surface, formation of a bacterial biofilm, and occurrence of compounds containing aldehyde groups during cultivation with NR latex gloves. Detailed analysis by means of scanning electron microscopy yielded further evidence for the two different microbial strategies and clarified the colonization efficiency. Thereby, strains VH2, Kb2, and NF4 directly adhered to and merged into the rubber material, while strain W2b produced mycelial corridors, especially on the surface of IR. Fourier transform infrared spectroscopy comprising the attenuated total reflectance technique was applied on NR latex gloves overgrown by cells of the Gordonia strains, which were the strongest rubber decomposers. Spectra demonstrated the decrease in number of cis-1,4 double bonds, the formation of carbonyl groups, and the change of the overall chemical environment, indicating that an oxidative attack at the double bond is the first metabolic step of the biodegradation process.
TL;DR: In this paper, a visco-hyperelastic constitutive equation is proposed to describe the large deformation response of incompressible rubber under high strain rates, which is able to aptly describe viscohype-relastic behaviour of rubber-like materials under high deformation rates.
TL;DR: In this paper, the roles of energy dissipation and crack deflection in rubber reinforcement are considered, and the final part of the review deals with nano-composite rubbers, in which rigid domain size is in the range of 1-10 nm.
Abstract: One of the most important phenomenon in material science is the reinforcement of rubber by rigid entities, such as dispersed particulate filler or phase-separated organic domains. In order to impart significant reinforcement, the size of the hard phase must be small, much less than a micron. The basis of this requirement is a major focus of this short review. Furthermore, the roles of energy dissipation and crack deflection in rubber reinforcement are considered. The final part of the review deals with nano-composite rubbers, in which rigid domain size is in the range of 1–10 nm.
TL;DR: In this article, Bagheri et al. examined the role of inter-particle distance in the fracture toughness in rubber/micro void toughened epoxies and found that fracture toughness goes through a ductile-to-brittle transition.
TL;DR: In this paper, an advanced micro-mechanical model of hyperelasticity and stress softening of reinforced rubbers is presented that combines a non-Gaussian tube model of rubber elasticity with a damage model of stress-induced filler cluster breakdown.
Abstract: An advanced micro-mechanical model of hyperelasticity and stress softening of reinforced rubbers is presented that combines a non-Gaussian tube model of rubber elasticity with a damage model of stress-induced filler cluster breakdown. The path integral formulation of rubber elasticity is briefly reviewed. Within this framework the consideration of tube-like, topological constraints (packing effects) as well as finite chain extensibility of rubber networks is described. The results are compared to the classical Mooney-Rivlin and inverse Langevin approaches of rubber elasticity. The effect of the filler is taken into account via hydrodynamic reinforcement of the rubber matrix by rigid, self-similar filler clusters, which leads to a cuantitative description of stress softening by means of a strain or pre-strain dependent hydrodynamic amplification factor, respectively. Thereby, the pronounced stress softening or high hysteresis of reinforced rubber is referred to an irreversible breakdown of filler clusters during the first deformation cycle. It is shown that the developed concept is in fair agreement with experimental data of unfilled NR-samples in uni-, equibiaxial and pare shear stretching mode. The pronounced stress softening of carbon black filled E-SBR- and EPDM-samples is well described on a quantitative level by an exponential filler cluster decay law.
TL;DR: In this article, the precipitation of three types of endfunctionalised liquid rubber (two CTBN and one ATBN) from two homologous series of amine-cured epoxy polymers with variable cross-link density was investigated.
TL;DR: In this article, the use of the sol-gel process on general-purpose grade rubbers is reviewed in the absence or presence of silane coupling agents, and the amount of silica formed was limited by the degree of swelling of the rubber vulcanizate by TEOS which was the precursor of the silica.
Abstract: The use of the sol—gel process on general-purpose grade rubbers is reviewed in the absence or presence of silane coupling agents. The sol—gel reactions of tetraethoxysilane (TEOS) in epoxidized natural rubber (ENR), styrene—butadiene rubber (SBR) or butadiene rubber (BR) vulcanizates produced silica generated in situ. This silica was found to be a good reinforcing agent by investigating tensile and dynamic mechanical properties and morphology observation by transmission electron microscopy (TEM). The amount of silica formed was limited by the degree of swelling of the rubber vulcanizate by TEOS which was the precursor of the silica. However, the dispersion of silica generated in situ was better than conventionally added silica due to its formation in place. Also, it was noted that the diameter distribution of in situ silica was monodispersed. Silane coupling agents, such as mercaptosilane, aminosilane, and bis(3-triethoxysilylpropyl) tetrasulfide, were compounded in the vulcanizates and their eff...
TL;DR: In this paper, the effects of dynamic crosslinking on rheological, mechanical and dynamic mechanical properties of high density polyethylene (HDPE) and acrylonitrile butadiene rubber (NBR) blends have been evaluated with special reference to the effect of dosage of crosslink agent.
Patent•
01 Sep 2000TL;DR: In this article, the authors proposed a vulcanization method based on a mixture of at least one rubber containing double bonds and at least two bismercaptan, and showed an improvement in the modulus level, a reduction in the DIN abrasion and a reduction of the heat build-up under dynamic stress.
Abstract: The invention relates to rubber mixtures of at least one rubber containing double bonds, at least one rubber gel and at least one masked bismercaptan, and to vulcanization products and rubber shaped articles produced therefrom. The vulcanization products produced from the rubber mixtures according to the present invention show an improvement in the modulus level, a reduction in the DIN abrasion and a reduction in the heat build-up under dynamic stress.
TL;DR: In this paper, the impact strength and tensile properties of Nylon 6 and maleated EPR-g-MA reinforced with glass fiber as a function of glass fiber and EPR g-MA content were examined.
TL;DR: In this article, the rheology, thermal and dynamic-mechanical properties and phase morphology of blends of polyamide 6 with natural rubber (NR) were explored, and the graft copolymer formation was investigated.
TL;DR: The structure development, rheological behavior, and viscoelastic proper-ties of carbon black-filled dynamically vulcanized thermoplastic elastomers based on the EPDM and polypropylene (PP) with the ratio range of 50/50 to 80/20 were studied and compared with similar but unfilled samples as discussed by the authors.
Abstract: The structure development, rheological behavior, and viscoelastic proper- ties of carbon black-filled dynamically vulcanized thermoplastic elastomers based on the ethylene-propylene- diene terpolymer (EPDM) and polypropylene (PP) with the ratio range of 50/50 to 80/20 were studied and compared with similar but unfilled samples. Two-phase morphology was observed at all ratios for the dynamically cured samples in which rubber particles are dispersed in the thermoplastic matrix. Carbon black distribution in each phase and damping behavior was found to be dependent upon the mixing condition and route of carbon black feeding. However, carbon black tends to stay mainly in the rubber phase, which leads to increase in the viscosity difference and, therefore, increase in the rubber particle size. Tensile strength and rupture energy increased with carbon black loading. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1127-1137, 2000
TL;DR: In this article, a novel approach to increase the lap joint strength was introduced, which is accomplished by the selective use of rubber toughening in epoxy to optimize lap joints strength.
Abstract: This paper introduces a novel approach to increasing the lap joint strength, different from the traditional methods of either increasing the lap joint area or altering the joint geometry. This is accomplished by the selective use of rubber toughening in epoxy to optimize lap joint strength. This was accomplished in three stages. In the first stage an adduct was prepared, this was used to make bulk tensile specimens to calculate the bulk properties for various concentrations of rubber, i.e. 0, 10, and 20 parts per hundred parts of resin (epoxy). In the second stage finite element models were developed using the bulk properties previously obtained. Interfacial stresses were used to access the trends obtained by the selective use of rubber toughening at different locations of the overlap in different configurations. The modeling of adhesive joints was done using ALGOR 2-D, linear and nonlinear finite element analyses (FEA). In the third stage, tensile shear tests conducted on the lap joints validated the tre...
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TL;DR: In this paper, a very simple experiment that demonstrates resonance is presented, which requires only two rubber bands of different sizes, a small piece of paper, and a plastic box, and can be used to explain radio and TV tuning.
Abstract: Here is a very simple experiment that demonstrates resonance. It requires only two rubber bands of different sizes, a small piece of paper, and a plastic box. This experiment helps students visualize resonance and can be exploited to explain radio and TV tuning by means of a simple mechanical analogy.
TL;DR: In this article, the effect of the blend ratio on the dynamic mechanical properties of SBR/NR blends was investigated at different temperatures and the storage modulus of the SBR blend decreased with increase of the temperature.
Abstract: Blends of styrene–butadiene rubber (SBR) and natural rubber (NR) were prepared and their morphology, transport behavior, and dynamic mechanical and mechanical properties were studied. The transport behavior of SBR/NR blends was examined in an atmosphere of n-alkanes in the temperature range of 25–60°C. Transport parameters such as diffusivity, sorptivity, and permeability were estimated. Network characterization was done using phantom and affine models. The effect of the blend ratio on the dynamic mechanical properties of SBR/NR blends was investigated at different temperatures. The storage modulus of the blend decreased with increase of the temperature. Attempts were made to correlate the properties with the morphology of the blend. To understand the stability of the membranes, mechanical testing was carried out for unswollen, swollen, and deswollen samples. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1280–1303, 2000
TL;DR: In this paper, Fourier-Transform Infrared Spectroscopy (FTIR) was used to analyze kraft lignin, a renewable waste material of pulp and paper industries.
Abstract: Lignin, a renewable waste material of pulp and paper industries, was analyzed through Fourier-Transform Infrared Spectroscopy (FTIR) and found to be structurally similar to kraft lignin. Surface modification by addition of benzoyl peroxide and subsequent heating at 70°C caused generation of new functional groups in lignin. Efficacy of the crude lignin as well as that of the modified variety as a filler in nitrile rubber (NBR) has been evaluated. Rubber vulcanizates were analyzed for physico-mechanical properties, oil and fuel resistance, and thermal stability, and compared with conventional fillers like phenolic resin and carbon black. Modified lignin has been found to produce superior elongation, hardness and compression set properties compared to phenolic resin but inferior to carbon black. Resistance to swelling, however, depends on the type of oil or fuel, and modified lignin always showed better properties than carbon black. Both thermo-gravimetric analysis (TGA) and thermo-mechanical analysis (TMA) showed highest thermal stability for the modified lignin followed by phenolic resin and carbon black.
TL;DR: In this paper, the effect of hydrothermal cycling on the water absorption behavior of a dicyandiamide cured silica filled rubber modified epoxy resin system is reported, and the dielectric and dynamic mechanical thermal analyses are carried out on samples, selected from the batches being exposed, at times which reflect various critical points in the ageing profile.
TL;DR: In this paper, photoageing at λ>300 nm (SEPAP, WOM, Xenotest), natural ageing (Bandol), and thermal ageing (100 and 150°C) were performed on EPDM rubber designed for automotive applications.
TL;DR: In this paper, the deformation and fracture behavior of several dynamic vulcanizate blends of isotactic polypropylene with EPDM was examined and compared with those of uncrosslinked blends of PP/EPDM.
Abstract: The deformation and fracture behavior of several dynamic vulcanizate blends of isotactic polypropylene with ethylene-propylene-diene rubber (EPDM) was examined and compared with those of uncrosslinked blends of PP/EPDM. These blends were prepared by melt mixing in an internal mixer at 190°C in a composition range of 10–40 wt % EPDM rubber. The variation in yield stress, the strength of fibrils of the craze, and the number density of the EPDM rubber domains (morphology fixation) that are dominant factors for enhancing interfacial adhesion and toughness in dynamic vulcanizate blends were evaluated. The ductility and toughness of these materials were explained in light of the composition between crack formation and the degree of plastic deformation through crazing and shear yielding. The physicomechanical properties including the hardness, yield stress, Young's modulus, percentage elongation, impact strength, flexural strength, and flexural modulus of dynamic vulcanized blends were found to be consistent and displayed higher values compared with uncrosslinked blends. The nucleation effect of the crosslinked particles and the decrease of crystallinity of the EPDM rubber were also considered to contribute to the improvement in the impact strength. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2089–2103, 2000