The influence of the interphase layer on the properties of isotactic polypropylene/ethylene-propylene rubber blends

The influence of an interphase layer formed by adding an oil to an ethylene -propylene synthetic rubber (EPR) on the structure of PP-EPR blends was stu died by electron microscopy. The presence of the oil affects the degree of dispersion of the rubber phase in the PP matrix. The melting temperature of PP in the blend decreases with increasing the proportion of oil-containing EPR. The compatibility parameter was determined from the dependence of the melting temperature on the rubber content using the Nishi-Wang equation. A negative value of the parameter indicates a limited compatibility of PP wi th oil-containing EPR. The latter also decreases the crystallization temper ature and the heat of crystallization of PP. The mechanical properties of t he blends were studied as functions of the temperature and rate of elongati on. The elastic modulus and the yield stress of the blends linearly depend on the logarithmic elongation rate. The activation volumes calculated with the Eyring equation increase with increasing rubber content, the increase b eing stronger for the oil-containing elastomer.