THE MELT COMPATIBILITY OF BLENDS OF POLYPROPYLENE AND ETHYLENE-PROPYLENE COPOLYMERS

Blends of polypropylene with ethylene-propylene copolymers of various compositions have been studied by small angle neutron scattering with regard to their compatibility at room temperature and in the melt. It has long been known that such blends separate into distinct phases at lower temperatures due to the crystallinity of the isotactic polypropylene. The work described herein has shown that these blends are also immiscible in the melt, even when the ethylene content of the copolymer is as low as 8 percent. Moreover, the separated phase domains grew rapidly at melt temperatures. Blends of atactic polypropylene with isotactic polypropylene did become miscible upon melting.