A Mechanism of Energy-Driven Elasticity in Crystalline Polymers

Abstract

It is proposed that a fundamental property of a folded-chain lamella is its ability to recover elastically from small deformations. The high degree of elastic recovery of certain extruded fibers and films of crystalline polymers is attributed to this property. Experiments on these elastic materials indicate that a common feature is a row structure of folded-chain lamellae joined together by short fibril links. Small deformations of individual lamellae are additive in the aggregate to produce a large deformation of the specimen without exceeding the elastic limit of the individual lamellae. Correspondingly, a phenomenal number of microvoids is created. These disappear with the elastic recovery of the specimen.

Experimental data show the elastic behavior is a consequence of energy-driven forces. Two alternate proposals for elastic behavior based on energy forces are offered: 1. bending of lamellae and 2. shearing of lamellae with van der Waal’s forces providing the driving force for recovery.