Showing papers on "Natural rubber published in 1988"

Principles of polymer engineering

Abstract: Introduction. 1: Structure of the molecule. 2: Structure of polymeric solids. 3: The elastic properties of rubber. 4: Viscoelasticity. 5: Yield and fracture. 6: Reinforced polymers. 7: Forming. 8: Design. Further reading, Answers, Index

A generalized criterion for rubber toughening: The critical matrix ligament thickness

Abstract: The thickness of matrix ligament is shown to be the single parameter determining whether a polymer/rubber blend will be tough or brittle. The matrix ligament is defined as the region of the matrix between two neighboring rubber particles. Specifically, the ligament thickness is the surface-to-surface interparticle distance. When the average ligament thickness is smaller than a critical value, a blend will be tough; when greater, it will be brittle. In other words, a sharp brittle–tough transition occurs at the critical ligament thickness. This critical parameter is independent of rubber volume fraction and particle size, and is characteristic of the matrix for a given mode, temperature and rate of deformation. What is important is the matrix ligament, not rubber particles. The single matrix parameter explains the effects of phase morphology, rubber volume fraction, particle size, particle-size polydispersity, and particle flocculation on toughness.

Natural rubber science and technology

Abstract: Foreword. Preface. A historical perspective of the rubber industry biosynthesis of rubber latex concentrates - properties and composition technological processing of natural rubber latex rheology of raw rubber compounding injection moulding compounding for tyres blends of natural rubber with thermoplastics chemical modification of natural rubber non-sulphur vulcanization sulphur vulcanization chemistry oxidative ageing graft copolymers from natural rubber strength properties of rubber friction and wear diffusion of liquids and solids in rubber low temperature crystallization of natural rubber engineering use of natural rubber vibration isolation and earthquake protection of buildings physical testing and automation chemical analysis the evolution of new uses for natural rubber. Index.

The electrical performance of polymeric insulating materials under accelerated aging in a fog chamber

Abstract: The materials evaluated in fog produced from low (250 mu s/cm) and high (1000 mu s/cm) conductivity water include cylindrical rod samples of high-temperature-vulcanized silicone rubber and ethylene-propylene-diene monomer rubber (EPDM) containing various amounts of either alumina trihydrate or silica fillers, or both. Comparison is made with material performance results obtained with AC, which was reported in an earlier study. In both low- and high-conductivity fog, the time to failure with AC and +DC was very similar, but a reduction by a factor of about four was observed in the time to failure with -DC. For both AC and DC, silicone rubber performed better than EPDM samples in low-conductivity fog, while the order of performance was reversed in high-conductivity fog. A theoretical model to determine the effect of dry band discharges on material is presented. Good agreement between the predicted behavior and the experimental findings is shown. >

Rubber contact urticaria. Allergenic properties of 19 brands of latex gloves.

Abstract: To compare the immediate skin test reactivity of various latex (natural rubber) surgical and cleaning gloves. prick tests were performed on 40 latex-allergic persons, 26 of whom were sensitized by surgical and 14 by cleaning latex gloves. 6/17 surgical gloves tested and 1/2 cleaning gloves caused positive reactions in almost all (over 87%) of the allergic subjects. In contrast. the frequencies of positive reactions to 4 other surgical latex gloves were us low as 8–21%, suggesting that not all surgical gloves arc equally allergenic. Control prick tests with I synthetic rubber and 1 polyvinyl chloride (PVC) glove were negative in all subjects. 2 surgical latex gloves causing either a high or low number of positive prick tests in allergic subjects were analyzed with high-pressure liquid chromatography (HPLC). Similar allergenic protein fractions were detected, which showed protein peaks at MW 2000 5000 and 3000 daltons. Corresponding proteins were detected in I latex cleaning glove analyzed and in natural rubber. This result confirms that allergnic proteins persist in various surgical and cleaning latex gloves after manufacture from natural rubber and may cause contact, urticaria symptoms toms in sensitized people.

High-tenacity conjugated fiber and process for preparation thereof

Abstract: A conjugated fiber having a sheath-core conjugated structure comprising a polyester core component composed mainly of polyethylene terephthalate and a polyamide sheath component composed mainly of polyhexamethylene adipamide, is disclosed, which has excellent mechanical properties such as a high tenacity, a high modulus, and an improved dimensional stability, and an improved adhesion to a rubber, especially a high-temperature adhesion, an improved heat resistance in a rubber, and a high fatigue resistance, and thus is useful as an industrial material. By adopting a high-speed spinning procedure in the fiber preparing process, the peel resistance in the interface of the sheath-core conjugated structure is greatly improved, and the following valuable characteristics not possessed by conventional conjugated yarns can be obtained: (1) Excellent adhesion and high-temperature adhesion comparable to those of a polyamide, which cannot be obtained in a polyester. (2) High modulus and dimensional stability comparable to those of a polyester, which cannot be obtained in a polyamide. (3) A heat resistance in a rubber and a fatigue resistance superior to those of a polyester.

Rubber Compounding: Principles: Materials, and Techniques, Second Edition

Abstract: Rubber compounding: principles, materials, and techniques , Rubber compounding: principles, materials, and techniques , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Rubber composition and golf ball comprising it

Abstract: A rubber composition comprising at least one natural and/or synthetic rubber component(s), fine inorganic fibers subjected to a surface treatment with a surface treating agent and a non-sulfur type vulcanizing agent and a golf ball comprising the composition which exhibits excellent durability, bounce impact elasticity and excellent feeling upon hitting.

Rubber composition for tires

Abstract: A rubber composition for tires having improved heat build-up and high temperature reinforcibility comprises specified amounts of particular surface-treated carbon black, silica and particular silane coupling agent based on 100 parts by weight of rubber ingredient.

Nonisothermal Vulcanization of Rubber Compounds

Abstract: In the present paper, progress has been made in developing a model for nonisothermal vulcanization of rubber compounds. The model is presently based on differential scanning calorimetry (DSC) measurements of heat evolved during vulcanization. The model parameters are determined from several isothermal DSC scans including measurements of induction time and rate of vulcanization. This model has conveniently been employed for a calculation of the temperature distribution during vulcanization of a rubber slab based on a one-dimensional heat-conduction equation with a heat-generation term. The simulation allowed us to predict the dynamics of the development of the state of cure distribution in the rubber slabs. Predicted results from the vulcanization model have been verified with experimental data on induction time and rate of vulcanization from nonisothermal DSC scans and with measurements of the state of cure distribution in rubber slabs cured under different vulcanization conditions between two he...

Rubber composition for tire tread

Abstract: This invention is a rubber composition for a tire tread of 100 parts by weight (pbw) diene system rubber to which are added x pbw of carbon black and y pbw of softening agent. The softening agent contains z pbw of liquid polymer. The amounts of x, y and z are described by the inequalities (5/8)x-20≦y≦x and (y/5)+5≦z. The liquid polymer has a flow points of 20° C. or below. The rubber composition provided here gives a tire tread with improved performance in terms of grade climbing ability, braking and standing start, on ice as well as on snow. Besides, the service life of the rubber is prolonged, and tread performance deterioration is reduced to a minimum.

Adherence and Rolling Kinetics of a Rigid Cylinder in Contact with a Natural Rubber Surface

Abstract: Equilibrium conditions of a rigid cylinder in contact with the flat and smooth surface of a natural rubber sample are studied using concepts of fracture mechanics, such as the strain energy release rate or the stress intensity factor. It is shown that an equilibrium contact area exists if the applied force per unit axial length is greater than a negative critical value, closely related to the cylinder radius and mechanical and superficial properties of the elastic solid. Due to the intervention of molecular attraction forces, of van der Waals type, a light cylinder rolls under an inclined rubber surface and it is displayed that the rolling speed is the same when the cylinder rolls upon the same inclined surface. It has been verified that if a flat rubber substrate, with an adequate length, is rotated at constant angular velocity, a steel cylinder rolls alternately upon and under the surface, unceasingly without falling down.

Dynamic Testing and Reinforcement of Rubber

Abstract: A series of experiments have been run to determine which mechanisms dominate carbon black reinforcement of rubber. A broad range of compounds using oil-extended and non-oil-extended rubbers and carbon blacks covering the spectrum of tread blacks have been tested. The results for measurements made in an all-SBR formulation are reported here. The primary experiment consisted of measurement of the dynamic modulus and hysteresis of the cured and uncured compounds over a broad range of frequencies, temperatures, and strains. Ternperatures ranged from −70°C to +90°C; frequencies varied from 0.01 to 10 Hz; double strain amplitudes varied from 0.5% to 35%. From a discussion of the literature and evaluation of the experimental results, two mechanisms have been found to control the primary effects of carbon black on rubber reinforcement, where reinforcement refers to a general enhancement of properties, such as modulus, as well as the tensile strength of the compound. Hydrodynamic interaction, which is the...

Modeling high-pressure gas-polymer mixtures using the Sanchez-Lacombe equation of state

Abstract: The Sanchez-Lacombe equation of state was used to model the sorption of high-pressure gases into solid, amorphous polymers and molten polymers. Only one adjustable parameter per binary pair, δ12, was used in the mixing rules to correct the deviation of the characteristic pressure of the mixture, P12*, from the geometric mean. The values of δ12 which gave the best fit of the available literature data for the carbon dioxide–polymethyl methacrylate, carbon dioxide–silicone rubber, ethylene–low density polyethylene, methane–polyisobutylene, methane–low-density and high-density polyethylene, and methane–polystyrene systems ranged from −0.019 to 0.136. In all cases, the calculated sorption isotherms were in reasonably good agreement with the experimental data. The resultant swelling of polymethyl methacrylate and silicone rubber was also well represented by the Sanchez-Lacombe equation of state. Because the Sanchez-Lacombe theory is based on lattice-fluid theory, the sorption calculations are limited to polymers which are noncrystalline, not cross-linked or slightly crosslinked, above their glass transition temperature, or above their melting temperature. The sorption data for the amorphous polymers considered in this study were either at temperatures above the glass transition temperature of the polymer or were at sufficiently high pressures that the temperature was above the effective glass transition temperature as predicted from a theoretical relation presented by Chow.

Production of hydroxyl‐terminated liquid natural rubber—mechanism of photochemical depolymerization and hydroxylation

Abstract: Photochemical degradation of natural rubber yielded hydroxyl-terminated liquid natural rubber (HTNR) when carried out in solution in presence of H2O2. Ultraviolet radiation from a medium pressure mercury vapor lamp and sunlight were found to be almost equally effective in bringing about the depolymerization and hydroxylation of natural rubber. The variations in the composition of the reagents and exposure time on the extent of depolymerization was conducted, and a suitable procedure for the large scale preparation of HTNR was described. A probable mechanism leading to the formation of HTNR as well as the side products is discussed based on the analytical data.

Tires made of silica filled, silane modified rubber

Abstract: There is a tire having tire performances such as wear resistance, cut resistance, heat build-up and the like and a processability simultaneously and economically improved by the application of a rubber composition containing a rubbery polymer modified with a silane compound and silica. The rubbery polymer modified with the silane compound is obtained by reacting an active terminal of a living polymer, which is obtained by polymerizing a monomer in the presence of an organic alkali metal catalyst, with a silane compound represented by the following general formula: X.sub.n Si(OR).sub.m R'.sub.4-m-n (where X is a halogen atom selected from a chlorine atom, a bromine atom and an iodine atom, OR is a non-hydrolyzable alkoxy group having a carbon number of 4˜20, an aryloxy group or a cycloalkoxy group, R' is an alkyl group having a carbon number of 1˜20, an aryl group, a vinyl group or a halogenated alkyl group, m is an integer of 1˜4, n is an integer of 0˜2, and a sum of n and m is 2˜4), which is contained in an amount of not less than 10% by weight as a rubber ingredient, and silica is contained in an amount of 5˜200 parts by weight based on 100 parts by weight of the rubber ingredient.

Rubber toughening of polystyrene through reactive blending

Abstract: Acrylonitrile-butadiene rubber having carboxylic acid groups (XNBR) and polystyrene having oxazoline groups, were melt blended in a Rheomix mixer under optimized conditions, The ratio of rubber to polystyrene phase was kept constant at 1:4 by weight. The concentration of the reactive oxazoline groups in the polystyrene phase was varied by mixing polystyrene (PS) with a copolymer of styrene and vinyl oxazoline (OPS). A torque rise observed during blending was found to be related to the concentration of oxazoline-carboxylic acid pairs. This torque rise, and independently measured increases in viscosity, both indicate inter-polymer crosslinkihg. Scanning electron microscopy was used to observe the morphology of the blends. Improved rubber phase dispersion was observed with increasing oxazoline concentration. Instrumented impact strength measurements were made using an unnotched Charpy technique. The plastic yielding was then quantified with the use of a ductility ratio. The impact strengths and ductility of the reactive blends are found to be up to 73% greater than those of the corresponding non-reactive blends. Increasing the OPS concentration beyond 5% results in decreasing impact strength, for as the compatibility increases, the rubber particle size decreases below an effective size for rubber toughening. Similar impact improvement is observed when the major PS phase is substituted with high impact polystyrene (HIPS) containing some OPS.

Adhesive thermoplastic elastomer blends

Abstract: The present invention relates to an adhesive thermoplastic elastomer composition comprising three major components as follows: (a) at least one polyolefin modified by a chemically reactive functional group such as a carboxylic acid or its derivatives including anhydride, acid chloride, isocyanate, oxazoline, epoxide, amine and hydroxide; (b) at least one other polymer prepared from one or more of the following: ethylene, propylene, butylene, isobutylene, octene-1, 4 methyl pentene-1, hexene-1 or mixtures; and (c) at least one olefinic elastomer, including elastomeric ethylene-propylene copolymers, elastomeric ethylene-propylene terpolymers, polyisoprene, polyisobutylene, ethylene-propylene copoloymer rubber, polybutadiene, natural rubber, elastomeric polyesters, polyurethane elastomers, polyamide elastomers and mixtures.

Miscible blends from rigid poly(vinyl chloride) and epoxidized natural rubber: Part 1 Phase morphology

Abstract: Etude des variations du couple de torsion Bradenberg et de la temperature lors du melangeage; etude de la densite, des proprietes dynamomecaniques et des thermogrammes de calorimetrie differentielle a balayage en fonction de la composition des melanges

Cohesive bonding process for forming a laminate of a wear resistant thermoplastic and a weather resistant rubber

Abstract: A polymer laminate produced by crosshead extrusion suitable for wear resistant applications such as a vehicle glass run channel comprises a layer of a weather resistant rubber such as an ethylene-propylenediene (EPDM) rubber and a layer of a wear resistant thermoplastic such as polypropylene The laminate is passed through an oven at an elevated temperature sufficient to cure the EPDM rubber, for example, at about 375° F, with ambient temperature cooling fluid being blown over the exposed surface of the polypropylene thermoplastic The interior polypropylene surface or interface is heated by the EPDM rubber which is at a high temperature as a result of the heat of extrusion and heat generated by cure thereof As a result, the polypropylene interior surface or interface melts and causes it to flow and form a mechanical bond with the EPDM rubber while the exposed surface as well as a substantial portion of the polypropylene is kept from melting by the cooling fluid The EPDM rubber can be extruded in the form of a channel having a longitudinal web which supports and is bonded to the laminated polypropylene wear strip to form a glass run channel

Thermoplastic resin composition

Abstract: THERMOPLASTIC RESIN COMPOSITION In the case where a polyamide is blended with a specific partially crosslinked graft-modified polyolefin elastomer obtained by dynamically heat-treating a blend of a peroxide-crosslinking olefin copolymer rubber and an olefinic plastic with an unsaturated carboxylic acid or derivative thereof, an unsaturated epoxy monomer or an unsaturated hydroxy monomer in the presence of an organic peroxide, if the graft-modified polyolefin plastomer occupies a major portion, a composition excellent in the oil resistance, the mechanical strength and the resistance against heat aging is obtained and if the polyamide occupies a major portion, a composition excellent in the impact resistance, the rigidity and the tensile strength is obtained.

Self-sealing pneumatic tire and method of manufacturing the same

Abstract: This invention relates to a pneumatic tire with puncture sealing properties and a method for manufacturing such a tire. In this method of manufacturing such a self-sealing pneumatic rubber tire a polymer composition layer is built into the tire in a relatively conventional manner. Under the conditions of heat and pressure used to cure the tire this polymer composition is both crosslinked and depolymerized to form a tacky material which has puncture sealant properties (the sealant layer). Ordinary tire manufacturing techniques can be employed since the sealant layer has the physical properties of ordinary butyl rubber used in tire building at the time it is assembled into the tire.

Cavitation in model elastomeric composites

Abstract: Layers of transparent silicone rubber were bonded between two steel spheres or between two parallel steel cylinders, to make simple mechanical models of particle-filled and fibre reinforced elastomers. When the steel end-pieces were pulled apart, visible cavities appeared suddenly in the rubber layer between them, at well-defined tensile loads and displacements. The critical conditions for cavity formation are shown to be in good agreement with a theoretical criterion for the unbounded elastic expansion of a microscopic precursor void within the rubber: that the local triaxial tensile stress attains a value of 5E/6, whereE is Young's modulus for the rubber. When the rubber layer was extremely thin, however, less than about 5% of the steel end-piece diameter, then the stress required to form a cavity was greater than this, and it increased rapidly as the rubber thickness was reduced further.

Remoldable, wood-filled acoustic sheet

Abstract: This invention is directed to a thermoplastic composition comprising polyolefin resin, cellulosic particulate and crosslinked elastomeric rubber microparticles, which composition can be extruded into sheets and subsequently remolded into three dimensional, thermoplastic articles having sound-deadening properties. Preferably, the polyolefin is polypropylene homopolymer and the cellulosic particulate is woodflour.

Modified rubber composition

Abstract: PURPOSE: To obtain a modified rubber composition increased in resiliency and decreased in JIS hardness at low temperature, by adding a modified diene polymer rubber obtained by reacting an alkali metal-containing diene polymer rubber with a specified aminosilane compound to a rubber component. CONSTITUTION: A rubber composition comprising a rubber component and additives, wherein said rubber component contains at least 10wt.% modified diene polymer rubber prepared by reacting either a diene polymer rubber having active alkali metal terminals or a conjugated diene rubber to which an alkali metal has been added with an aminosilane compound of formula 1. In formula 1, R 1 , R 2 and R 3 are each alkyl or alkoxy, R 4 and R 5 are each alkyl, and n is an integer. As said aminosilane compound, 3-dimethyl aminopropyldiethoxymethylsilane is particularly preferable. COPYRIGHT: (C)1988,JPO&Japio

Pneumatic tire with tread of styrene, isoprene, butadiene rubber

Abstract: A styrene, isoprene, butadiene terpolymer rubber with a characterization according to its glass transition temperatures and unit structure and a pneumatic tire with a tread composed of such terpolymer rubber specifically in combination with selected other rubber which has been observed to provide such tread with enhanced physical properties.

Ternary polymer blends containing a polyetherimide, a polyphthalate carbonate, and rubber modified vinyl aromatic polymer

Abstract: The present invention relates to ternary polymer blends containing (a) a polyetherimide, (b) a rubber modified vinyl aromatic polymer, and (c) a polyphthalate carbonate. The blends have excellent high temperature properties, improved impact resistance values and have excellent flexural values.

Fluorosilicone rubber composition

Abstract: The fluorine-substituted organopolysiloxane as the principal ingredient of the inventive silicone rubber composition has vinyl groups to serve as the cross-linking points at the molecular chain terminals while at least the penultimate siloxane unit or the silicon atom adjacent to the terminal silicon atom has no fluorine-substituted hydrocarbon group bonded to the silicon atom. Being freed from the steric hindrance due to the bulky fluorine-substituted hydrocarbon group bonded to the adjacent silicon atom, the vinyl group bonded to the terminal silicon atom can pertain to the cross-linking reaction much easier than otherwise so that the silicone rubber composition of the invention containing an organic peroxide or a combination of an organohydrogenpolysiloxane and a platinum catalyst as a curing agent can be rapidly cured to give a cured silicone rubber article having excellent resistance against oils and organic solvents as well as mechanical properties.