Showing papers on "Nitrile rubber published in 2002"

Physical studies of foamed reinforced rubber composites Part I. Mechanical properties of foamed ethylene–propylene–diene terpolymer and nitrile–butadiene rubber composites

Abstract: Reinforced ethylene–propylene–diene terpolymer (EPDM) and nitrile–butadiene rubber (NBR) blends were compounded with different concentrations of azodicarbonamide (ADC/K) foaming agent to obtain foamed EPDM and NBR composites. The mechanical properties under compression and under extension at different temperatures were measured for these foams. It was found that the increase of foaming agent concentration and temperature affect all the mechanical parameters. The obtained stress–strain data are discussed in the light of the continuum mechanics theory for compressible materials. © 2002 Society of Chemical Industry

Process for the preparation of low molecular weight hydrogenated nitrile rubber

Abstract: Pursuant to the invention a process for the production of hydrogenated nitrile rubber polymers having lower molecular weights and narrower molecular weight distributions than those known in the art in the is provided wherein the process is carried out in the presence of hydrogen and optionally at least one co-(olefin). The present invention further relates to the use of specific metal compounds in a process for the production of a hydrogenated nitrile rubber by simultaneous hydrogenation and metathesis of a nitrile rubber.

Low molecular weight hydrogenated nitrile rubber

Abstract: The present invention relates to hydrogenated nitrile rubber polymers having lower molecular weights and narrower molecular weight distributions than those known in the art. Another object is the use of said nitrile rubber for the manufacture of shaped articles.

Effect of Elastomeric Nanoparticles on Toughness and Heat Resistance of Epoxy Resins

Abstract: A new composite consisting of epoxy resin and elastomeric nanoparticles with high toughness and high heat-distortion temperature is prepared. The size of the nanoparticles used was less than 90 nm. The excellent properties of the composite seem to be due to stronger interactions between the carboxyl groups of the nanoparticles and the epoxy groups of the resin, and to enhanced hydrogen bonding between the nitrile groups of the rubber and the hydroxyl groups of the resin.

UV curable elastomer composition

Abstract: Ethylene copolymer elastomer compositions, acrylate rubber compositions, nitrile rubber compositions, fluoroelastomer compositions, and chlorinated olefin elastomer compositions are provided which are curable by exposure to UV radiation. The compositions are particularly suited for production of elastomeric seals using hot melt equipment and a gasketing in place technique.

Silica reinforcement of synthetic diene rubbers by sol–gel process in the latex

Abstract: Styrene-butadiene rubber (SBR) and nitrile rubber (NBR) were reinforced with silica by the sol-gel method of tetraethoxysilane (TEOS) in latex. The sol-gel reaction proceeded in the mixture of latex, TEOS, water, and a catalyst. The compound that involved silica was crosslinked with the curing agent at 150°C. The amount of TEOS added and the molar ratio of TEOS to water ([H 2 O]/[TEOS]) in the mixture were related to the silica content in the compounds, particle size, and reinforcing behavior of silica. The particle size and reinforcing behavior of the silica were greatly influenced by the amount of TEOS and [H 2 O]/[TEOS]. The diameter of the dispersed silica particles in cured rubbers was controlled by the amount of TEOS and [H 2 O]/[TEOS], which were smaller than 100 nm. By the dispersion of the fine silica in the nanometer-order level, the tensile strength of the compound was drastically improved. The tensile strength of SBR was over 30 MPa, and of NBR, over 25 MPa. Compounds with a high tensile strength had a high bound rubber fraction and a very strong interaction of the fine silica with rubber.

Ionic elastomers based on carboxylated nitrile rubber (XNBR) and zinc peroxide: Influence of carboxylic group content on properties

Abstract: The properties of ionic elastomers formed in the crosslinking with zinc peroxide are studied in compounds with varying proportions of carboxylic groups in the elastomeric matrix. At the temperature used, 150°C, preferentially ionic bonds were formed. The crosslinking densities and, correspondingly, the physical properties, increased with the acid group content and with the reaction time. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 605–615, 2002; DOI 10.1002/app.10313

Oil resistant thermoplastic elastomers of nitrile rubber and high density polyethylene blends

Abstract: Different grades of oil resistant thermoplastic elastomers (TPE) based on blends of nitrile rubber (NBR) and high density polyethylene (HDPE) have been developed. Chemical treatment of HDPE to evolve compatibility with NBR and dynamic vulcanization with different curatives have been studied. Determination of physico-mechanical and thermal properties and relative crystallinity of these blends have been carried out. Oil resistance characteristics of the blends have been evaluated in different commercially used oils and fuels for applications as a substitute for NBR/polyvinyl chloride (PVC) blends.

Radiation vulcanization of acrylonitrile–butadiene rubber with polyfunctional monomers

Abstract: The efficiency of six polyfunctional monomers (PFMs) as crosslinking coagents for radiation vulcanization of acrylonitrile–butadiene rubber (NBR) by electron beam was studied. It was found that among the polyfunctional monomers having same functionality, short chain PFMs are better than long chain PFMs. Comparison is also made to select more efficient PFMs among methacrylates and acrylates for radiation vulcanization of NBR. The methacrylate monomers showed preference over acrylate monomers. Physical properties of NBR are greatly improved by PFMs at lower doses. Radiation vulcanization of NBR with diethyleneglycol dimethacrylate (2G), at 20 kGy showed results similar to those obtained by conventionally vulcanized NBR.

Low molecular weight nitrile rubber

Abstract: The present invention relates to nitrile rubber polymers having lower molecular weights and narrower molecular weight distributions than those known in the art. Another object is a process for the manufacture of said nitrile rubber and the use of said nitrile rubber for the manufacture of shaped articles.

Dynamic mechanical behavior of acrylonitrile butadiene rubber/poly(ethylene‐co‐vinyl acetate) blends

Abstract: The dynamic mechanical behavior of uncrosslinked (thermoplastic) and crosslinked (thermosetting) acrylonitrile butadiene rubber/poly(ethylene-co-vinyl acetate) (NBR/EVA) blends was studied with reference to the effect of blend ratio, crosslinking systems, frequency, and temperature. Different crosslinked systems were prepared using peroxide (DCP), sulfur, and mixed crosslink systems. The glass-transition behavior of the blends was affected by the blend ratio, the nature of crosslinking, and frequency. sThe damping properties of the blends increased with NBR content. The variations in tan δmax were in accordance with morphology changes in the blends. From tan δ values of peroxide-cured NBR, EVA, and blends the crosslinking effect of DCP was more predominant in NBR. The morphology of the uncrosslinked blends was examined using scanning electron and optical microscopes. Cocontinuous morphology was observed between 40 and 60 wt % of NBR. The particle size distribution curve of the blends was also drawn. The Arrhenius relationship was used to calculate the activation energy for the glass transition of the blends, and it decreased with an increase in the NBR content. Various theoretical models were used to predict the modulus of the blends. From wide-angle X-ray scattering studies, the degree of crystallinity of the blends decreased with an increasing NBR content. The thermal behavior of the uncrosslinked and crosslinked systems of NBR/EVA blends was analyzed using a differential scanning calorimeter. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1556–1570, 2002

Epoxidized natural rubber as a reinforcement modifier for silica-filled nitrile rubber

Abstract: Hydrated silicas impart better physical properties to polar rubbers, compared to those of hydrocarbon rubbers. However, to achieve optimum properties silane coupling agents are crucial in such formulations. Epoxidized natural rubber (ENR) in small proportions is used as a reinforcement modifier for silica-filled nitrile rubber (NBR). Two systems of cure were used: N-cyclohexyl- 2-benzthiazyl sulfenamide (CBS) alone and in combination with diphenyl guanidine (DPG). In the CBS accelerated system, incorporation of an optimum concentration of about 15% of ENR on total rubber was found to improve technological properties. Addition of a secondary accelerator further improves these properties. Comparable results are obtained with those containing coupling agent and NBR–ISAF. High bound rubber and volume fraction values indicate a high polymer–filler interaction and gel content resulting from the NBR–ENR interaction. Results of this study reveal that ENR could be used as a reinforcement modifier for the NBR–silica system. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 292–306, 2002

Toughening of vinylester–urethane hybrid resins through functionalized polymers

Abstract: Liquid nitrile rubber, hyperbranched polyester, and core/shell rubber particles of various functionality, namely, vinyl, carboxyl, and epoxy, were added up to 20 wt % to a bisphenol-A-based vinylester–urethane hybrid (VEUH) resin to improve its toughness. The toughness was characterized by the fracture toughness (Kc) and energy (Gc) determined on compact tensile (CT) specimens at ambient temperature. Toughness improvement in VEUH was mostly achieved when the modifiers reacted with the secondary hydroxyl groups of the bismethacryloxy vinyl ester resin and with the isocyanate of the polyisocyanate compound, instead of participating in the free-radical crosslinking via styrene copolymerization. Thus, incorporation of carboxyl-terminated liquid nitrile rubber (CTBN) yielded the highest toughness upgrade with at least a 20 wt % modifier content. It was, however, accompanied by a reduction in both the stiffness and glass transition temperature (Tg) of the VEUH resin. Albeit functionalized (epoxy and vinyl, respectively) hyperbranched polymers were less efficient toughness modifiers than was CTBN, they showed no adverse effect on the stiffness and Tg. Use of core/shell modifiers did not result in toughness improvement. The above changes in the toughness response were traced to the morphology assessed by dynamic mechanical thermal analysis (DMTA) and fractographic inspection of the fracture surface of broken CT specimens. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 672–680, 2002; DOI 10.1002/app.10392

Belt fabric, and power transmission belt and high load power transmission V-belt using such a belt fabric

Abstract: A belt fabric which is provided at a part of a power transmission belt on which frictional forces act is formed by dipping into a rubber solution prepared by dissolving a non cross-linked hydrogenated nitrile rubber composition, mixed with a polyethylene powder having a molecular weight in excess of 1 million and an organic peroxide as a cross-linking agent, in a solvent.

Crosslinking of Rubbers by Fillers

Abstract: Oxygen containing chemical groups on the carbon black surface can react with the carboxyl groups of XNBR, or epoxy groups of ENR, or chlorosulfonated groups of CSM, during high temperature molding of the rubber-filler mixtures. This leads to crosslinking of the rubber phase. The extent of crosslinking increases if the carbon black surface is oxidized, the concentration of the reactive groups of the rubber increases, or a suitable silane coupling agent is incorporated in the rubber-filler mixtures. Similarly, high temperature molding of the XNBR-precipitated silica, ENR-precipitated silica, CSM-precipitated silica, and CR-ferrite mixtures leads to crosslinking of the rubber phases, even in the absence of conventional rubber vulcanizing agents. XNBR-ZnO mixture on high temperature molding also produces crosslinked rubbers consisting of ionic crosslinks. During mixing stage, the reactive fillers interact with the polar rubbers leading to formation of high bound rubber, presumably through hydrogen bo...

Properties of silica‐filled styrene‐butadiene rubber compounds containing acrylonitrile‐butadiene rubber: The influence of the acrylonitrile‐butadiene rubber type

Abstract: Because silica has strong filler-filler interactions and adsorbs polar materials, a silica-filled rubber compound exhibits poor dispersion of the filler and poor cure characteristics in comparison with those of a carbon black-filled rubber compound. Acrylonitrile-butadiene rubber (NBR) improves filler dispersion in silica-filled styrene-butadiene rubber (SBR) compounds. The influence of the NBR type on the properties of silica-filled SBR compounds containing NBR was studied with NBRs of various acrylonitrile contents. The composition of the bound rubber was different from that of the compounded rubber. The NBR content of the bound rubber was higher than that of the compounded rubber; this became clearer for NBR with a higher acrylonitrile content. The Mooney scorch time and cure rate became faster as the acrylonitrile content in NBR increased. The modulus increased with an increase in the acrylonitrile content of NBR because the crosslink density increased. The experimental results could be explained by interactions of the nitrile group of NBR with silica.

The effect of mercapto‐modified EVA on rheological and dynamic mechanical properties of NBR/EVA blends

Abstract: The effect of mercapto-modified ethylene vinyl acetate copolymer (EVALSH) on the rheological and dynamic mechanical properties of acrylonitrile butadiene rubber (NBR) and ethylene vinyl acetate copolymer (EVA) blends was evaluated at different blend compositions. The addition of 5 phr of EVALSH in the blends resulted in an increase of the melt viscosity and a substantial decrease of the extrudate swell ratio. These results can be attributed to the interactions occurring between the double bond of the NBR phase and the mercapto groups along the EVALSH backbone. The power–law index also presents a slight increase in the presence of EVALSH, indicating a decrease in the pseudoplastic nature of the compatibilized blends. The reactive compatibilization of NBR/EVA blends with EVALSH was also confirmed by the decrease of damping values and an increase of glass transition temperature, in dynamic mechanical analysis. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2335–2344, 2002

In situ preparation of magnesium methacrylate to reinforce NBR

Abstract: Magnesium methacrylate (MDMA) was in situ prepared in nitrile rubber (NBR) by reacting magnesium hydroxide (Mg (OH)2) with methacrylic acid (MAA) during the mixing step. The formation of MDMA in NBR was proved by the wide-angle X-ray diffraction analysis (WAXD). The mechanical properties, crosslinking structure, and morphology of the resulting peroxide-cured NBR vulcanizates were studied. Results showed that Mg (OH)2/MAA mixtures had a great reinforcing effect for NBR, and their amounts and ratio played important roles in influencing the ultimate properties. Both the covalent crosslink density and ionic crosslink density of the vulcanizates were measured. And the nano-composite morphology of such vulcanizates was also observed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1403–1408, 2002; DOI 10.1002/app.10323

Unsaturated polyester as compatibilizer for styrene–butadiene (SBR)/acrylonitrile–butadiene (NBR) rubber blends

Abstract: The effect of the addition of 5 and 10 phr of unsaturated polyester resin (UPE) on the compatibility and physicomechanical properties of styrene–butadiene (SBR) and acrylonitrile–butadiene (NBR) rubber blends was studied. Differential scanning calorimetry (DSC), scanning electron microscopy (SEM), electrical, and ultrasonic techniques were used to determine the degree of the compatibility (DC). The results obtained revealed that, by the addition of 10 parts per hundred parts of rubber (phr) UPE as a compatibilizer for SBR/NBR blends, the degree of compatibility was greatly enhanced. The rheological and mechanical properties of the blends were also improved. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2314–2321, 2002

Vibration damping materials based on interpenetrating polymer networks of carboxylated nitrile rubber and poly(methyl methacrylate)

Abstract: Interpenetrating polymer networks (IPNs) based on carboxylated nitrile rubber (XNBR) and poly(methyl methacrylate)s were synthesized. Crosslinked XNBR was swollen in methyl methacrylate containing benzoyl peroxide as initiator and tetraethylene glycol dimethacrylate as crosslinking agent. The compositions of the IPNs were varied by changing the swelling time of the rubber in the methacrylate monomer. The dynamic mechanical properties of the IPNs were studied. The dynamic mechanical properties in the range 1–105 Hz were obtained by the time-temperature superposition of the data under multifrequency mode, which indicated high tan δ with good storage modulus in the entire frequency range. This indicates the suitability of these IPNs as vibration and acoustic dampers. Copyright © 2002 John Wiley & Sons, Ltd.

Rubber modified vinyl ester resins of different molecular weights

Abstract: The morphology, as well as the related fracture and mechanical behavior of vinyl ester resins (DVER) of different molecular weights cured with styrene (S) and modified with two different liquid rubbers are presented and discussed. The liquid rubbers are: carboxyl terminated poly(butadiene-co-acrylonitrile) (CTBN), a common toughening agent for epoxy resins, and an almost unreactive rubber with the DVER and S comonomers, and a reactive rubber (vinyl terminated poly(butadiene-co-acrylonitrile), (VTBN). The initial miscibility of the modified systems and the reactivity of the rubber determine the final morphology of the material. This morphology will correspond to a continuous main phase (rich in the DVER-S copolymer) with simple rubber rich inclusions (as in the epoxy-rubber systems) or with inclusions with a complex internal structure, where phase separation occurs as in the low profile modified unsaturated polyester resins. The morphologies developed are strongly dependent on the resin molecular weight as well as on the elastomer added. In spite of the initially higher compatibility of the S-DVER-CTBN system with respect to the S-DVER-VTBN system, the reactivity of the vinyl-ended elastomer leads to a much finer distribution of the elastomeric phase. In particular, the low molecular weight resin cured with S and modified with 10% of CTBN leads to a cocontinuous structure with microvoids that generates a material of low density and poor mechanical and fracture properties. On the other hand, the use of VTBN as additive leads to a more compact morphology, with gradual reduction of the mechanical performance of the modified resins and improved fracture behavior.

Effect of temperature on the crosslink densities of nitrile rubber and carboxylated nitrile rubber with zinc peroxide

Abstract: We studied the crosslinking of conventional nitrile rubber with metal peroxide at varying temperatures. Crosslink density, measured by swelling in the solvent until equilibrium, and the reaction rate increased with temperature, suggesting that crosslinking is a function of peroxide decomposition. At a specific reaction time, some peroxide remained in the unreacted form in the final product. This was not observed when the reaction temperature was sufficiently high to achieve total decomposition of the peroxide (190–200°C). When a carboxylated nitrile rubber was crosslinked, the same results were obtained. However, in this case, exclusively ionic or a combination of ionic and covalent crosslinks were generated, depending on the vulcanization temperature used. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 335–340, 2002

Studies on Acrylonitrile Butadiene Rubber/Reclaimed Rubber Blends:

Abstract: Cure characteristics and mechanical properties of acrylonitrile butadiene rubber/reclaimed rubber blends were studied. Minimum torque, (maximum -minimum) torque, scorch time, cure time and cure rate decreased in presence of reclaimed rubber. Tensile strength, elongation at break and compression set increased with increase in reclaim content. Resilience and abrasion resistance decreased with reclaim loading. Heat build up was higher for the blends. The ageing resistance of the blends was inferior to that of the gum compound.

Effects of trans‐polyoctylene rubber on rheological and green tensile properties of natural rubber/acrylonitrile–butadiene rubber blends

Abstract: The influence of trans-polyoctylene rubber (TOR) on the flow property, die swell behaviour and green tensile property of NR (natural rubber)/NBR (acrylonitrile–butadiene rubber) blend compound was investigated as a function of TOR loading level. The pure TOR, NR and NBR compounds were also investigated for comparison with the blend compounds. The shear viscosity of TOR strongly depended on the temperature as well as shear rate. The viscosity of the NR/NBR blend compound was even lower than that of the constituent components at relatively lower shear rates, and the viscosity difference became smaller as the shear rate was increased. The viscosity of the NR/NBR blend compounds was strongly affected by the addition of TOR but the effect became negligible with increasing the shear rate. Both the die-swell ratio and the surface topology of extrudates were also affected by TOR addition; the dependence on shear rate was much stronger for higher TOR level. The NR/NBR blend compound showed much higher green tensile strength and elongation at break than those of the constituent components. Both the green tensile modulus and strength of the NR/NBR blend compound were greatly enhanced, while the elongation at break was reduced with the addition of TOR. © 2002 Society of Chemical Industry

Aqueous resin adhesive composition having pre-bake resistance

Abstract: An aqueous adhesive composition, as for bonding nitrile rubbers to a metal substrate, has very good pre-bake resistance. The adhesive composition comprises a phenolic novolac or resole resin, chlorinated natural rubber, a reactive fillers, and precipitated silica. Utilization of the adhesive composition results in essentially failure of the nitrile rubber.