THE ORIGIN OF HETEROEPITAXY IN THE SYSTEM OF UNIAXIALLY ORIENTED ISOTACTIC POLYPROPYLENE AND POLYETHYLENE

The epitaxy of polyethylene (PE) on oriented alpha and beta-form of isotactic polypropylene (PP) at different crystallization temperatures and rates have been investigated. The result shows that the epitaxy of PE on beta-form of PP does not differ from that on the alpha-form of PP. The epitactic alignment of the PE lamellae on the PP films becomes more perfect with higher crystallization rates of PE. The epitaxy of PE on alpha- or beta-form of PP does not occur at crystallization temperatures higher than 123-degrees-C. A nucleation controlled process for the alignment of the PE is proposed.