STRUCTURE AND PROPERTIES OF PROPYLENE-ETHYLENE BLOCK COPOLYMERS AND THE CORRESPONDING BLENDS

Structure and properties of presumed polypropylene(PP)‐b‐polyethylene(PE) block copolymers (PPPE) and the corresponding blends (PP/PE) have been investigated by wide‐angle x‐ray scattering (WAXS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), torsional pendulum apparatus, and other techniques measuring mechanical properties. Crystallinity, morphological structure, and mechanical properties of the block copolymers and blends vary with the PP and PE compositions. Compared with PP homopolymers and PP/PE blends, PP and PE segments in PP‐PE block copolymers have a reduced crystallinity, especially PE segments. An additional peak at about −40°C is observed in dynamic relaxation spectra; substantially different morphology is revealed; and mechanical properties are greatly improved for the sequentially copolymerized PP‐PE block copolymers, indicating the existence of PP‐PE block structure. Copyright © 1990 John Wiley & Sons, Inc.