Phase separation and crystallization behavior in extruded polypropylene/ethylene-propylene rubber blends

Liquid-liquid (GL) phase separation and its effects on crystallization in p olypropylene (PP)/ethylene-propylene rubber (EPR) blends obtained by melt e xtrusion were investigated by time-resolved light scattering (TRLS) and opt ical microscopy. GL phase separation via spinodal decomposition (SD) was co nfirmed by TRLS data. After L-L phase separation at 250 degreesC for variou s durations, blend samples were subjected to a temperature drop to 130 degr eesC for isothermal crystallization, and the effects of GL phase separation on crystallization were investigated. Memory of the GL phase separation vi a SD remained for crystallization. The crystallization rate decreased with increasing GL phase-separated time at 250 degreesC. Slow crystallization fo r the long GL phase-separated time could be ascribed to decreasing chain mo bility of PP with a decrease in the EPR component in the PP-rich region. Th e propylene-rich EPR exhibited good affinity with PP, leading to a slow gro wth of a concentration fluctuation during annealing, (C) 2001 John Wiley & Sons, Inc.