Showing papers on "Natural rubber published in 2002"

Recent Advances in the Theory of Filler Networking in Elastomers

Abstract: The viscoelastic properties of (mostly carbon black) filled elastomers are reviewed with emphasis on the strain-dependence of the complex dynamic modulus (Payne effect) Considerable progress has been made in the past in relating the typical dynamical behavior at low strain amplitudes to a cyclic breakdown and reagglomeration of physical filler-filler bonds in typical clusters of varying size, including the infinite filler network Common features between the phenomenological agglomeration/deagglomeration Kraus approach and very recent semi-microscopical networking approaches (two aggregate VTG model, links-nodes-blobs model, kinetical cluster-cluster aggregation) are discussed All semi-microscopical models contain the assumption of geometrical arrangements of sub-units (aggregates) in particular filler network structures, resulting for example from percolation or kinetical cluster-cluster aggregation These concepts predict some features of the Payne effect that are independent of the specific types of filler These features are in good agreement with experimental studies For example, the shape exponent m of the storage modulus, G′, drop with increasing deformation is determined by the structure of the cluster network Another example is a scaling relation predicting a specific power law behavior of the elastic modulus as a function of the filler volume fraction The exponent reflects the characteristic structure of the fractal filler clusters and of the corresponding filler network The existing concepts of the filler network breakdown and reformation appear to be adequate in describing the deformation-dependence of dynamic mechanical properties of filled rubbers The different approaches suggest in a common manner that there is a change of filler structure with increasing dynamic strain However, in all cases additional assumptions are made about the accompanying energy dissipation process, imparting higher hysteresis to the filled rubber This process may be slippage of entanglements (slip-links) in the transition layer between bound rubber layer and mobile rubber phase, and/or partially release of elastically ‘dead’ immobilized rubber trapped within the filler network or agglomerates

Material Properties Bamboo fibre filled natural rubber composites: the effects of filler loading and bonding agent

Abstract: Bamboo fibre reinforced natural rubber composites were prepared by incorporation of different loadings of bamboo fibre. Two series of composites were studied i.e. composites with and without the presence of a bonding agent. The curing characteristics of the composites were determined and the composites were vulcanized at 150°C using a hot press. The properties of the composites such as tensile strength, tensile modulus, tear strength, elongation at break and hardness were studied. The adhesion between the bamboo fibre and the natural rubber were enhanced by the addition of bonding agent as exhibited by the tensile fracture surfaces of the composites using scanning electron microscopy (SEM). The presence of bonding agent also gave shorter curing time and enhanced mechanical properties.  2001 Elsevier Science Ltd. All rights reserved.

Organically Modified Layered Silicates as Reinforcing Fillers for Natural Rubber

Abstract: Rubber compounds based on natural rubber containing organically modified montmorillonites were prepared. The state of dispersion of the clay was characterized by scanning and transmission electron microscopies, and the spacings between the silicate layers were evaluated by X-ray diffraction. The effect of the addition of clay on the elastomeric compound was analyzed through mechanical and swelling properties and also through the determination of polymer chain orientation during elongation.

New Insights into Structural Development in Natural Rubber during Uniaxial Deformation by In Situ Synchrotron X-ray Diffraction

Abstract: Molecular orientation and strain-induced crystallization of vulcanized natural rubber during uniaxial deformation were studied via in situ synchrotron wide-angle X-ray diffraction (WAXD) The high intensity of synchrotron X-rays and new image analysis methods made it possible to estimate mass fractions of the strain-induced crystals and the amorphous chains in both oriented and unoriented states Contrary to the conventional conception, it was found that, in highly stretched natural rubber, most chains remained unoriented in the amorphous phase; only a few percent of the amorphous chains were oriented and the rest of the chains were in the crystalline phase This indicates that stress induces a network of microfibrillar crystals that is responsible for the elastic properties The new information has prompted us to reconsider the relationships of molecular orientation, induced crystallization and mechanical behavior in natural rubber

Rubber composition usable as a tire tread

Abstract: The present invention relates to a cross-linkable or cross-linked rubber composition having improved hysteresis properties in the cross-linked state which is useful for constituting a tire tread, to a process for preparation of such a cross-linkable composition, to a tread of this type and to a tire having reduced rolling resistance. The rubber composition according to the invention is based on: an elastomeric matrix comprising at least one diene elastomer which comprises a carboxylic acid function at one or at each of its two chain ends, and a reinforcing filler comprising a reinforcing inorganic filler, wherein said diene elastomer has a molecular weight which is greater than 80,000 g/mol, and it is present in a majority quantity in said elastomeric matrix.

Conjugated diolefin (co)polymer rubber, process for producing (co)polymer rubber, rubber composition, composite, and tire

Abstract: A conjugated diolefin (co)polymer rubber formed from either a conjugated diolefin or a conjugated diolefin and an aromatic vinyl compound and having a primary amino group and alkoxysilyl group bonded to the (co)polymer chain It has satisfactory processability and can give an automotive tire tread having a balance among wearing resistance, failure characteristics, low hysteresis loss, and wet skid characteristics

Louisiana experience with crumb rubber-modified hot-mix asphalt pavement

Abstract: A comparative study of laboratory and field performance of several applications of crumb rubber-modified (CRM) hot-mix asphalt in Louisiana is presented. Eight CRM asphalt pavement sections were constructed by eight different CRM processes or applications. These eight CRM sections were built at five state highway projects. A control section with conventional asphalt mixture was constructed at each project to compare with the performance of pavement sections built with CRM asphalt mixtures. To evaluate the mixture characteristics of the CRM and conventional mixes, laboratory tests of Marshall stability and flow, indirect tensile strength and strain, and indirect tensile resilient modulus were conducted on field compacted Marshall specimens. Comparisons of the field performances of the pavements were achieved through roadway core air void analysis, rut-depth measurement, international roughness index, pavement structure numbers measured through the Dynaflect (dynamic deflection determination) system, and vi...

Use of rice husk ash as filler in natural rubber vulcanizates: In comparison with other commercial fillers

Abstract: Rice husk ash is mainly composed of silica and carbon black remaining from incomplete combustion. Both silica and carbon black have long been recognized as the main reinforcing fillers used in the rubber industry to enhance certain properties of rubber vulcanizates, such as modulus and tensile strength. In this study, two grades of rice husk ash (low- and high-carbon contents) were used as filler in natural rubber. Comparison was made of the reinforcing effect between rice husk ashes and other commercial fillers such as talcum, china clay, calcium carbonate, silica, and carbon black. Fourier transform infrared spectroscopy (FTIR) analysis was employed to study the presence of functional groups on the ash surface. The effect of silane coupling agent, bis(3-triethoxysilylpropyl)tetrasulfane (Si-69), on the properties of ash-filled vulcanizates was also investigated. It was found that both grades of rice husk ash provide inferior mechanical properties (tensile strength, modulus, hardness, abrasion resistance, and tear strength) in comparison with reinforcing fillers such as silica and carbon black. However, the mechanical properties of the vulcanizates filled with rice husk ash are comparable to those filled with inert fillers. The addition of silane-coupling agent has little effect on the properties of the ash-filled vulcanizates. This is simply due to the lack of silanol groups on the ash surface. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2485–2493, 2002

Preparation and properties of EPDM/organomontmorillonite hybrid nanocomposites

Abstract: Hybrid nanocomposites based on organophillic montmorillonite (MMT) and ethylene–propylene–diene rubber (EPDM) have been prepared by a melt compounding process. From analysis by X-ray diffraction and transmission electron microscopy, the rubber molecules were found to be intercalated into the galleries of organoMMT and the silicate layers of organoMMT are uniformly dispersed as platelets of 50–80 nm thickness in the EPDM matrix. Dynamic mechanical studies reveal a strong rubber–filler interaction in the hybrid nanocomposite which is manifested in the lowering of tan δ at the glass transition temperature. The hybrid nanocomposites exhibit great improvement in tensile and tear strength, and modulus, as well as elongation-at-break. Moreover, the permeability of oxygen for the hybrid nanocomposite was reduced remarkably. © 2002 Society of Chemical Industry

Influence of Different Silanes on the Reinforcement of Silica-Filled Rubber Compounds

Abstract: The silane modification of precipitated silica for rubber applications is state-of-the-art. Usually, bifunctional silanes are used to provide a silica-to-rubber coupling. In this paper, th...

Liquid crystal display device and method of manufacturing for the same

Abstract: PROBLEM TO BE SOLVED: To sufficiently prevent occurrence of a defect by contact of a sealing material before curing and a liquid crystal material and to substantially prevent an increase of process step burden for restriction on the selection range of the sealing material and sealing material arrangement in the liquid crystal display device and the method of manufacturing for the same which include a process for arranging the liquid crystal material on any substrate prior to the combination of an array substrate and the counter substrate. SOLUTION: An array substrate 1 is provided thereon with spacer projections 15 and simultaneously the points enclosing pixel regions 3 are provided with two pieces of parallel fence-like projections 11 and 12 of approximately the same projecting dimensions as those of the spacer projections 15. A counter substrate 2 is provided, thereon, with a piece of fence-like projection 21 which is formed of a material having rubber like elasticity and is slightly larger in the projecting height than that of the spacer projections 15. After the liquid crystal material 4 is dropped to the central part of the pixel regions 3, the array substrate 1 and the counter substrate 2 are combined and are bonded, following which the liquid crystal display panel 10 is coated with a sealing material 5 from its end face side.

Hydrophobic particulate inorganic oxides and polymeric compositions containing same

Abstract: Described are hydrophobic particulate inorganic oxides useful for reinforcing polymeric composition, e.g., rubber. The materials are characterized by: (a) the substantial absence of functional groups capable of chemical reaction with rubber; (b) a BET surface area of in the range of from 40 to 350 m2/g; (c) a hydroxyl content in the range of 2 to 15 OH/nm2; (d) a carbon content in the range of from 0.1 to 6 percent by weight that is substantially non-extractable; (e) a pH in the range of from 3 to 10; (f) an M1 Standard White Area less than 0.4 percent and (g) a methanol wettability of from 15 to 45 percent. Compositions such as polymers, cured organic rubber articles, master batches and slurries containing the hydrophobic fillers are also described.

Rubber composition for tire tread and pneumatic tire using the same

Abstract: The present invention provides a rubber composition for a tire capable of improving gripping performance of a tire and a tire using the rubber composition. More specifically, the present invention relates to a rubber composition for a tire tread comprising 1 to 150 parts by weight of a piezoelectric material, based on 100 parts by weight of a natural rubber and/or a diene synthetic rubber and a tire using the rubber composition for a tire tread. The average particle size of the piezoelectric material is preferably 0.01 to 50 μm.

Reinforcement of natural rubber

Abstract: In this article, we report on recent investigations on filled natural rubber. These investigations include a mechanical characterization as well as a molecular analysis based on measurements of chain orientation. It is demonstrated that at intermediate strains, the increase in the moduli can be explained by the inclusion of rigid particles in the soft matrix and from molecular interactions between the rubber and the filler. These interactions can be evaluated by equilibrium swelling and by orientational measurements. With regard to the unfilled formulation, carbon black– and silanized-filled natural rubber exhibit increases in the cross-linking density ascribed to filler-polymer links, whereas a large decrease in the orientational level, evidenced by birefringence and by infrared dichroism, is observed when silica is added without any coupling agent. Finally, two specific effects—the Payne and Mullins effects, both related to energy dissipation phenomena—are discussed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2301–2316, 2002

Effect of axial stretching on electrical resistivity of short carbon fibre and carbon black filled conductive rubber composites

Abstract: The variation of electrical resistivity of carbon black and short carbon fibre (SCF) filled rubber composites was studied against the degree of strain at constant strain rate. It was found that both the degree of strain and strain rate affect the electrical resistivity of the composites. The change in resistivity against the strain and strain rate depends both on the concentration and the type of conductive filler. The incorporation of short carbon fibres (SCF) imparts higher conductivity to the composite than carbon black at the same level of loading. Composites filled with carbon black exhibit better mechanical properties than SCF filled composites. Electrical setting, ie a permanent change in electrical resistivity, was observed during extension–retraction cycles. A good correlation was found between the mechanical response and the electrical response towards strain sensitivity. The results of different experiments are discussed in the light of breakdown and formation of conductive networks in the filled rubber composites. © 2002 Society of Chemical Industry

Properties of polymer modified bitumen after rubber-bitumen interaction

Abstract: This paper describes results from a laboratory investigation into the effects of the interaction between a styrene-butadiene-styrene (SBS) modified bitumen and recycled crumb rubber on the mechanical performance of impact absorbing asphalt (IAA), an asphaltic material that has applications as a sports and safety surface. Curing tests at high temperatures have been undertaken using different rubber-bitumen ratios to assess the amount of bitumen absorbed by the rubber. The changes in bitumen constitution through this interaction have been monitored and related to changes in the rheological characteristics of the residual bitumen. The results show that significant absorption takes place and that the residual bitumen undergoes alterations in terms of its stiffness and viscoelastic balance, together with a reduction in cohesion. A significant finding has been the loss of the polymeric nature of the residual SBS polymer modified bitumen. This has been due to the precipitation of the SBS polymer as the compatibi...

Recycling technology of tire rubber

Abstract: Material recycling technology for automotive tire rubber waste was developed by the continuous devulcanization method. The deodorization during the recycling process has become possible by the newly developed method. The devulcanized rubber obtained by these methods from tire rubber waste, generated from both the manufacturing products and scrap tires, shows excellent mechanical properties applicable to the new tire rubber compounds in engineering practice. Furthermore, it was confirmed by actual road tests that a test truck tire containing 10 wt % of the devulcanized rubber in the tread might exhibit tread wear behavior almost equal to that for the standard type with the new rubber compound.