A dynamic mechanical thermal analysis (DMTA) study of polyethylenes

Abstract

Differences in mechanical α and β relaxations for a family of six polyethylenes (PE) are discussed in terms of structural variations and immobilization of amorphous chains. An amorphous contribution has been identified in the α transition of high density polyethylenes (HDPE). Further, low density polyethylenes (LDPE) with long chain branches are found to sustain more amorphous tension than their linear low density analogs; such tension may be attributed to additional restraints in amorphous regions. Effects of CCl 4 plasticization on the two relaxations are discussed in terms of chain immobilization and free volume. Our data support the assignment of the β transition as the primary glass transition in PE. Relations between relaxation and mechanical toughness of the PE family are also discussed.