A Dislocation Mechanism for Deformation in Polyethylene

Abstract

A mechanism is proposed for transverse slip on {100} 〈010〉 in polyethylene, in terms of the motion and multiplication of dislocations caused by chain ends. Some of these defects, the jogged dislocations, are able to move at stresses somewhat below the yield stress. However, the extent of transverse slip and of the resulting transverse textures is limited by chain folds and the requirement of chain continuity. Slip displacements parallel to the chain direction are then favored. The mismatch requirements for dislocations with Burgers vectors having components in the chain direction are determined. The Burgers vectors are 〈0, b, nc〉 on {100} and 〈a, b, nc〉 on {110}; the latter can dissociate into two types of partials with Burgers vectors 〈a/2, b/2, nc〉 or 〈a/2, b/2, (n−½)c〉, where n=1, 2⋯. Such defects can act in pairs [u, v, w] and [ū, v̄, w] producing displacements parallel to the chain direction.