THE CHARACTERIZATION OF RANDOM PROPYLENE-ETHYLENE COPOLYMER

The comonomer sequence distribution of a propylene-ethylene random cop olymer has been investigated by a combination of temperature rising el ution fractionation, C-13 nuclear magnetic resonance spectroscopy, Fou rier transform infrared spectroscopy and differential scanning calorim etry (d.s.c.). The propylene-ethylene copolymer exhibited a wide range of comonomer compositional heterogeneity and there were no detectable long ethylene sequences containing three or more adjacent ethylene un its in any of the fractions. The copolymer was mainly composed of long propylene sequences with an occasional ethylene unit. Sequences such as PPE, EPE, and PEP were present. The sequence distributions of all t he fractions did not fit either Bernoullian or first order Markovian s tatistics. The ethylene content and the comonomer distribution had a m arked effect on the crystallisation kinetics and melting behaviour of the fractions. (C) 1998 Elsevier Science Ltd. All rights reserved.