Propylene Random Copolymer Research Articles

Development of the γ-crystal form in random copolymers of propylene and their analysis by dsc and x-ray methods

Random copolymers of propylene with minor proportions of ethylene, butene and other comonomers develop γ-form crystallinity, mixed with α-form, on crystallisation from near the melting point. The proportion of γ-form increases with comonomer content. γ-form determinations, together with measurement of degrees of crystallinity by x-rays and melting point distributions by differential scanning calorimetry ( dsc), after carefully controlled thermal treatment, can be used to characterize the chain distribution present. The effect of thermal history on the melt distribution observed by dsc and the α γ ratio has been investigated in detail for one copolymer containing 6·5mol% ethylene, and the crystal morphology developed in this copolymer and fractions obtained by solvent extraction is discussed.