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Abstract: Solvent resistance properties of nano-structured layered silicates filled natural rubber (NR), carboxylated styrene butadiene rubber (XSBR) and their 70/30 latex blend were investigated by equilibrium swelling method using benzene, toluene and p-xylene. The layered nano-structured sodium bentonite and sodium fluorohectorite were used in the present study. The impact of concentration of filler, temperature and penetrant size on the transport properties of aromatic solvents through layered silicates reinforced latex membranes were analysed. The transport properties of filled latex membranes was analysed as a function of extent of exfoliation of the layered silicate in the rubber matrix. The morphology of filler dispersion in the rubber matrix was analysed from transmission electron micrographs. More exfoliated structure was found in sodium-fluorohectorite filled latex membrane. The extent of intercalation of polymer chain into the layers of silicates was estimated using X-ray diffraction technique. The enhanced d-spacing in latex nanocomposite indicated the intercalated structure. Nanocomposite of natural rubber (NR), carboxylated styrene butadiene rubber (XSBR) and their blends showed reduced swelling rate due to the tortuosity of the path and the reduced transport area in polymeric membrane. [Copyright &y& Elsevier]

Abstract: The thermal stability of natural rubber (NR) and carboxylated styrene butadiene rubber (XSBR) latices and their blends was studied by thermogravimetric methods. Ageing characteristics of these latex blends were studied by applying hot air oven thermal ageing for seven days at 70°C. The mechanical properties of the aged samples were studied. Thermal degradation and ageing properties of these individual latices and their blends were investigated with special reference to blend ratio and vulcanization techniques. As the XSBR content in the blends increased their thermal stability was also found to increase. Among sulphur and radiation-vulcanized samples, radiation cured possesses higher thermal stability due to the higher thermal stability of carbon–carbon crosslinks. DTG curves were used for the determination of different stages involved in the degradation. Activation energy for degradation was determined from Coats–Redfern plot. The properties of aged samples were found to decrease due to chain depletion. However, the moduli of XSBR and NR/XSBR blends were found to increase owing to the formation of crosslinks upon ageing. [Copyright &y& Elsevier]

Abstract: The gas permeability coefficient of nano and micro composites of natural rubber, carboxylated styrene butadiene rubber and 70:30 natural rubber/carboxylated styrene butadiene rubber blend membranes has been investigated with special reference to type of filler, gases, filler loading and pressure. The layered silicates such as sodium bentonite and sodium fluorohectorite were the nanofillers used and the conventional micro fillers were clay and silica. Latex nanocomposites were characterized by X-ray diffraction technique. The dispersion of layered silicates in the polymer matrix was analysed using transmission electron microscopy. The fluorohectorite silicate showed excellent dispersion in natural rubber matrix. The effect of free volume on the gas barrier properties was investigated by positron annihilation lifetime spectroscopy. It was observed that due to the platelet like morphology and high aspect ratio of layered silicates, the gas barrier properties of nano filled latex membranes were very high. The crosslink density values and extent of reinforcement were estimated in order to correlate with the gas barrier properties. The oxygen/nitrogen selectivity of these membranes were investigated. The diffusion of gas molecules through the polymer was determined by time-lag method and diffusion selectivity of the membranes was computed. [Copyright &y& Elsevier]