S. K. De

Quantitative estimation of filler distribution in immiscible rubber blends by mechanical damping studies

Abstract The peak value of tan δ at the glass-transition temperature (Tg) in the plot of tan δ versus temperature is lowered on addition of filler to a rubber. This relative lowering of tan δ at Tg can be used to estimate the filler distribution in an immiscible rubber blend. In the present investigation, distribution of silica filler and carbon black was studied in blends of natural rubber (NR) and epoxidized natural rubber (ENR). It was observed that silica migrated preferentially to the ENR phase. The magnitude of the distribution depends on filler loading and the epoxy content of ENR. The amount of carbon black migrated to the NR phase is higher than that of silica at a similar loading in blends of NR and ENR.

Bonding between precipitated silica and epoxidized natural rubber in the presence of silane coupling agent

Results of Monsanto rheometic studies and measurements of physical properties reveal that precipitated silica interacts chemically with epoxidized natural rubber (ENR) during high temperature (180°C) molding and the extent of chemical interaction increases in the presence of silane coupling agent, namely N-3(N-vinyl benzyl amino) ethyl-γ-amino propyl trimethoxy silane monohydrogen chloride. Fourier transform infrared spectroscopic studies show that silica is bonded to ENR through formation of Si—O—C bond, whereas in the presence of silane coupling agent, silica is bonded to the coupling agent through Si—O—Si bond, and ENR is bonded to the coupling agent through C—N—C bond formation.

Studies on thermal degradation of short melamine fibre reinforced EPDM, maleated EPDM and nitrile rubber composites

This paper reports the results of studies on the thermal and ablative properties of the vulcanizates based on EPDM, maleated EPDM and nitrile rubber reinforced with melamine fibre, one of the recent generation high performance fibres. The thermogravimetric studies of the composites show that the presence of melamine fibre in the vulcanizates reduces the rate of decomposition and the effect is pronounced in the presence of the dry bonding system consisting of resorcinol, hexamethylene tetramine and silica. The first degradation step of the vulcanizate is controlled by the fibre, whereas the fibre as well as the matrix contributes to the second degradation step. An increase in fibre loading decreases the rate of degradation and weight loss in the second degradation step. The rate of decomposition of NBR vulcanizates is lower than those based on EPDM and maleated EPDM rubbers. The activation energy of decomposition of the vulcanizates is increased, if fibre is properly adhered to the matrix in the presence of the dry bonding system. The crosslinking system also affects the activation energy of decomposition, especially for the second degradation step. Melamine fibre causes significant reduction in the thermal erosion rate of the vulcanizates. The fibre filled composites, in the presence of the dry bonding system, display a lower thermal erosion rate compared to those containing no dry bonding system, showing that proper adhesion between the fibre and the matrix is important to achieve improved ablative properties. Among the three matrices, the vulcanizates based on nitrile rubber display the lowest thermal erosion rate.

Influence of surface oxidation of carbon black on its interaction with nitrile rubbers

Abstract Interactions of carbon black with nitrile rubber (NBR) and carboxylated nitrile rubber (XNBR) were studied by measurements of bound rubber, physical and dynamic mechanical properties of the vulcanizates and Monsanto rheometric studies on the rubber—filler mixes. Compared with NBR, XNBR shows a higher degree of interaction with the filler and oxidation of the filler surface increases the extent of the rubber—filler bonding, which involves weak hydrogen bonding and Van der Waals forces. In the case of XNBR additional chemical bonding occurs between the −COOH groups of the rubber and the reactive groups on the filler surface.

Characterization of ground rubber tire and its effect on natural rubber compound

Abstract Ground rubber tire (GRT) particles of different sizes were characterized and the effect of these particles in a natural rubber (NR) compound was studied. It is found that smaller particles contain less polymer, but have higher amounts of fillers and metals with respect to polymer. NR compound containing smaller GRT particles shows better physical properties, but poorer aging characteristics.

Effect of silane coupling agent on the chemorheological behaviour of epoxidised natural rubber filled with precipitated silica

Abstract Results of measurements of physical properties and solvent swelling of the extrudates indicate that epoxidised natural rubber (ENR) interacts chemically with precipitated silica when the mix of the two was extruded at 150–170°C in a Monsanto Processability Tester (MPT). The extent of interaction between the rubber and the filler depends on the extrusion time, the volume fraction of the filler, the shear rate and the addition of the silane coupling agent, namely N-3-(N-vinyl benzyl amino) ethyl-γ-amino propyl trimethoxy silane monohydrochloride. The activation energy of the chemical interaction between ENR and silica decreases on the addition of the silane coupling agent.

Bonding between epoxidized natural rubber and clay in presence of silane coupling agent

Based on the results of bound-rubber determination, Monsanto rheometric studies, solvent swelling, measurement of physical properties, and infrared spectroscopic studies, it is revealed that epoxidized natural rubber (ENR) and hard clay interact chemically to form Si–O–C bond during high-temperature (180°C) molding. It is also observed that addition of the silane coupling agent N-3-(N-vinyl benzyl amino)ethyl-γ-amino propyl trimethoxy silane monohydrogen chloride enhances the extent of the chemical interaction with the formation of coupling bonds of Si–O–Si type between clay and the coupling agent and C–N bonds between ENR and the coupling agent.

Dynamic mechanical spectroscopic studies on plasticization of an ionic elastomer based on carboxylated nitrile rubber by ammonia

Results of measurements of dynamic mechanical and physical properties of the ionic polymer, based on carboxylated nitrile rubber (XNBR) neutralized by zinc oxide (ZnO), reveal that ammonia works as an ionic plasticizer. Accordingly, the main chain transition is little affected but the high temperature transition due to ionic aggregates, as observed in dynamic mechanical measurements, disappeared after being exposed to ammonia for 24 h. Exposure to ammonia also caused a drop in physical properties of both unfulfilled and carbon black and silica filled XNBR-ZnO compositions.

Interaction between carboxylated nitrile rubber and precipitated silica : Role of (3-aminopropyl)triethoxysilane

Abstract On the basis of measurements of bound rubber and physical properties and the results of Monsanto rheometer, dynamic mechanical and infrared spectroscopic studies, it is observed that strong rubber-filler interaction occurs between XNBR and precipitated silica filler. During molding, XNBR was found to be crosslinked by the filler surface through the formation of primary bonds. The coupling agent, namely (3-aminopropyl)triethoxysilane facilitates the formation of rubber-filler bonds at the expense of filler-filler networks, leading to improved dispersion and enhanced degree of crosslinking.

Ionic thermoplastic elastomer based on maleated epdm rubber. I. Effect of zinc stearate

Neutralization of maleated EPDM rubber by zinc oxide results in an ionic elastomer. The rate and extent of the neutralization reaction increase by addition of stearic acid. Although the rubber is not easy processable as such, incorporation of zinc stearate at a loading of 30 phr makes the rubber behave the rubber behave like a thermoplastic during high temperature (≥ 150°C) processing. Furthermore, zinc stearate causes improvement in the physical properties of the rubber under ambient conditions. It is believed that zinc stearate acts as a reinforcing filler under ambient conditions and as a plasticizer for the ionic domains at higher temperature (that is, above its melting point, 128°C). The conclusions are based on the results of dynamic mechanical, rheological, and infrared spectroscopic studies.