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Thermomechanical reactive blending of silicone rubber and LLDPE: Effects of processing parameters



To prepare thermoplastic elastomers based on linear low density polyethylene (LLDPE) and silicone rubber (SR) the reactive blending of the two polymers was carried out at different processing conditions. Effects of mixing parameters such as temperature, shear rate, mixing time, and sequence of feeding the ingredients, upon the yield and rate of interfacial reaction, have been evaluated by following the variation of mixing torque and also by determination of the reacted fraction of silicone rubber. The yield and rate of the reaction increased by increasing the temperature of mixing, shear mixing rate, and the time of mixing. Changing the sequence of feeding the ingredients also changed the yield of the reaction. First feeding of polyethylene increased the yield of reaction. According to the obtained results, interfacial reaction between two phases is limited by chemical kinetics of the reaction and by rate of mass transfer during melt mixing. The order of interfacial reaction between these two polymers under thermomechanical conditions was found to be about 1.1. Rheological studies on the blends performed by using rheomechanical spectroscopy showed a distinct rheological behavior with a non-Newtonian characteristic and higher dynamic viscosity at low frequencies for the blends prepared at high temperature and shear rate. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 155–161, 2005