Transitions in ethylene polymers

Abstract

Abstract A study of polyethylenes and ethylene–vinyl acetate copolymers by dynamic mechanical mesurements gives new information on the transitions in polyethylene polymers. The melting points agree with the predictions of Flory's theory. The alpha transition is shown to be due to the melting of crystallites containing ethylene sequences of lengths near the average sequence lengths; this transition is related to the lengths of crystallites. The beta transition is not necessarily due to branch points, as a number of noncrystallizable groups produce beta transitions at the same temperature. The beta transition degenerates into the gamma transition if the crystallinity is destroyed.