BLENDS OF AMORPHOUS-CRYSTALLINE BLOCK-COPOLYMERS WITH AMORPHOUS HOMOPOLYMERS - MORPHOLOGICAL-STUDIES BY ELECTRON-MICROSCOPY AND SMALL-ANGLESCATTERING

A morphological study was performed with symmetric diblock ethylene-pr opylene copolymer (DEP) and the binary blends made from DEP and atacti c polypropylene (APP) by use of small angle X-ray, light and neutron s cattering, and also scanning and transmission electron microscopy. DEP contains a crystallizable polyethylene block and an amorphous atactic polypropylene block. Quenching the blends in liquid nitrogen preserve d the morphology in the melt state. This quenching technique revealed that DEP forms a lamellar microdomain structure and blending DEP and A PP includes morphological changes in the microdomain structures as wel l as macrophase separation. When the APP chain was shorter than the AP P block, the addition of APP changed the morphology from a lamellar to a bicontinuous cylindrical and then a discrete cylindrical and finall y to a spherical structure. On the other hand, when the APP chain was longer than the APP block, macrophase separation was observed and only a transition from a lamella to a bicontinuous cylinder occurred. Thes e morphological transitions in the melt state can be correlated to dif ferences in the crystallization kinetics of the blends. Copyright (C) 1996 Elsevier Science Ltd.