MORPHOLOGY OF POLYMER BLENDS.

Abstract

Results of an experimental program are presented, in which blends of PE, PP, and EPDM rubber were injection- and compression molded and examined by electron microscopy. Because EPDM, and PE and PP are incompatible, they separate into discrete phases in the molten state during molding. On cooling, the PP matrix solidifies first (T//m equals 171 degree C). Subsequently, the droplets of PE solidify (T//m equals 138 degree C) and shrink away from the surrounding PP. EPDM which is initially mixed in the PE droplets appears to become interposed between PE and PP on prolonged heating during compression molding. It is demonstrated that fine dispersions of EPDM, PE and PP can be prepared by injection and compression molding. The texture of compression molded samples varied with molding time.