The measurement of compositional heterogeneity in a propylene–ethylene block copolymer

¹³C nuclear magnetic resonance (n.m.r.) and Fourier transform infra-red (FTi.r.) spectroscopies, as well as wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (d.s.c.) and temperature rising elution fractionation (TREF), have been combined to measure the composional heterogeneity of a commercial propylene–ethylene block copolymer. It has been shown that the copolymer contains molecular species with a wide variation in composition, and the copolymer products range from amorphous ethylene–propylene rubbers (EPR) to crystallisable propylene–ethylene statistical copolymers, polyethylene and polypropylene homopolymers as well as blocks of various lengths. The so-called block copolymer was composed of about 15% amorphous EPR, 5% random copolymer, 28% block copolymers with long propylene and long ethylene sequences, and 52% homopolypropylene. The crystallisation and melting behaviour of these fractions have been investigated.