Fractionation and characterisation of propylene-ethylene random copolymers: Effect of the comonomer on crystallisation of poly(propylene) in the γ-phase

Abstract

Three propylene-ethylene random copolymers, of varying ethylene content, were fractionated using preparative TREF. The TREF fractions were subsequently analysed offline by CRYSTAF, DSC, 13CNMR spectroscopy, HT-GPC, and WAXD. The effect of the ethylene comonomer on the crystallisability of the propylene was investigated, along with the effect of the comonomer on the type of crystal phase formed during the crystallisation. The results show that the comonomer inhibits the crystallisation of the copolymer and that as the ethylene content increases, the crystallisation and melting points decrease. It was also shown that the higher the ethylene content, the more of the γ-phase crystal type is formed. The inter-molecular distribution of the ethylene comonomer and stereo errors vary between the samples analysed, and this accounts for the relative differences in crystallisation behaviour of the samples. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA.