Properties of ethylene–propylene–vinyl chloride graft copolymers. I. Viscoelasticity of ethylene–propylene copolymers

The viscoelastic behavior of two different ethylene–propylene copolymers was studied as a function of the molar ratios of the components and the distribution of the lengths of the ethylene and propylene sequences. The glass transition temperatures T_g agree with the values calculated from relations between T_g and component ratio established by other authors. The copolymer with longer ethylene and propylene sequences was found to exhibit a relaxation spectrum with a slope less steep than ?0.5. This broadening is explained by the broader distribution of friction factors of the statistical segments in this copolymer and by differences in crystallike nearest-neighbor packing.