DYNAMIC-MECHANICAL BEHAVIOR ANALYSIS FOR LOW ETHYLENE CONTENT POLYPROPYLENE COPOLYMERS

Dynamic mechanical behavior of low ethylene content propylene-ethylene copolymers was studied. It was found that there exists ethylene-propy lene rubber component in the block copolymer, which is accordance with the component analysis. It is suggested that it is because of the exi stence of the ethylene-propylene rubber component that the block copol ymer exhibits high impact strength. The relaxation temperature shifted to lower temperature for copolymers compared with homopolymer, and th e damping peak was broadened by copolymerization, consistent with the increased chemical heterogeneity of the copolymers. Effects of thermal history and frequency on the relaxations were studied. The activation enthalpy for relaxation was determined. (C) 1998 John Wiley & Sons, I nc.