P. P. De

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

Miscible blends of rigid poly(vinyl chloride), PVC, and epoxidized natural rubber (ENR) having 50 mol % epoxidation level, are prepared in a Brabender Plasticorder by the melt-mixing technique. Changes in Brabender torque and temperature, density, dynamic mechanical properties and DSC thermograms of the samples are studied as a function of blend composition. The PVC-ENR blends behave as a compatible system as is evident from the singleTg observed both in dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). The moderate level broadening of theTg zone in blends is due to microinhomogeneity, which may arise from the particle structures of PVC perturbing the molecular level mixing of PVC and ENR. Scanning electron microscopic studies were conducted on nitric acid-etched samples and the results showed continuous structures of blend components as well as the occurrence of solvent-induced cracks in high PVC blends.

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.

Reinforcement of EPDM-based ionic thermoplastic elastomer by carbon black

Abstract High abrasion furnace carbon black improves the physical properties of zinc sulfonated ethylenepropylenediene terpolymer of high (75 wt%) ethylene content. Properties studied include hardness, stress-strain characteristics, tear strength, hysteresis and abrasion resistance. Scanning electron photomicrographs of the tear fractured and abraded surfaces show changes in failure mode of the polymer on incorporation of carbon black. Results of dynamic mechanical analyses and dielectric thermal analyses show that carbon black reinforces the ionomers, presumably through weak rubber—filler interaction involving the backbone chains and strong interaction between the active sites of the filler surface and the ionic aggregates present in the ‘multiplets’ and ‘clusters’. Reprocessability studies in the Monsanto Processability Tester (MPT) show that the carbon black filled polymer can be reprocessed like a thermoplastic elastomer and there was no fall in properties even after three cycles of extrusion through the MPT.

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.

Homogeneous catalytic Hydrogenation of natural rubber using RhCl(PPh3)3

Hydrogenation is an important method of chemical modification, which improves the physical, chemical, and thermal properties of diene elastomers. It is also a useful method for preparation of polymers with unusual monomer sequences. Natural rubber (NR) could be quantitatively hydrogenated to a strictly alternating ethylene-propylene copolymer using a homogeneous RhCl(PPh3)3 catalyst. The effect of concentration of rubber, catalyst and triphenyl phosphine, temperature, pressure, and solvent on the course of hydrogenation were evaluated. The thermal properties of the hydrogenated NR are compared with NR.

Thermal characterization of mica-filled thermoplastic polyurethane composites

Abstract Thermoplastic polyurethane–mica composites were prepared in a Brabender Plasticorder at 180°C by melt mixing and their thermal properties were studied. The thermal stability of the thermoplastic polyurethane improved marginally on incorporation of mica, which shifted the decomposition temperature of the composite to a higher level, thus delaying the degradation. ©

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.

Degradation of Hydrogenated Styrene—Butadiene Rubber at High Temperature

Abstract Degradation of hydrogenated styrene—butadiene rubber (HSBR) having different levels of unsaturation has been studied over a wide range of temperatures under anaerobic and aerobic conditions using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), IR and NMR spectroscopy. TGA data indicate higher thermal stability of hydrogenated rubber as compared to SBR in nitrogen, although an anomalous behavior is observed in air due to crosslinking and oxidation of styrene—butadiene rubber (SBR). Isothermal data confirm the above observations. IR and NMR results reveal thermal isomerization, cyclization, oxidation, depolymerization, and chain scission processes. The nature and amount of products formed depend on the time and temperature of degradation and also on the level of hydrogenation of SBR.

Thermoplastic elastomeric hydrogenated styrene-butadiene elastomer : Optimization of reaction conditions, thermodynamics, and kinetics

Thermoplastic elastomeric hydrogenated styrene—butadiene (HSBR) elastomer was prepared by diimide reduction of styrene-butadiene rubber in the latex stage. The products were characterized by infrared, 1H-NMR, 13C-NMR spectroscopy, and differential scanning calorimetry (DSC). The standard free energy change, ΔG0 at 298°K is −44.7 × 104 kJ/mol, indicating that the formation of HSBR is thermodynamically feasible. The value of heat change of the reaction at constant volume, ΔUT is −41.6 × 104 kJ/mol. The effect of different reaction parameters on the level of hydrogenation, calculated from nuclear magnetic resonance spectroscopy, was also investigated. The degree of hydrogenation increases with the increase in reaction time, temperature, the concentration of reactants and catalyst. A maximum of 94% hydrogenation was obtained under the following conditions: time, 4 h; temperature, 45 ± 2°C; pH, 9.36; cupric sulphate (CuSO4 · 5H2O) catalyst concentration, 0.0064 mmol; hydrazine concentration, 0.20 mol; and hydrogen peroxide concentration, 0.26 mol. The diimide reduction of SBR is first-order with respect to olefinic substrate, and the apparent activation energy is 9.5 kJ/mol. The glass transition temperature increases with the increase in saturation level due to development of crystalline segments.