On the Deformation of Polycarbonate in the Glassy State

Abstract

Thermoplastics are usually processed in the molten state either by extrusion or by injection moulding techniques (1). Although an additional drawing step, for instance for a film or a fiber, may be performed in the solid state in order to achieve a preferential orientation of the chain molecules, this will happen at temperatures above the glass transition temperature. In principal it is of course also possible to process thermoplastics in the solid state at temperatures below the glass transition temperature of amorphous materials and at temperatures below the melting temperature of partially crystalline materials (2-7). Cold working is a well known technique in the area of metallurgy. It has, however, been applied to thermoplastics only in a limited number of special cases. The deformation to which the samples are subjected are well outside the range of the linear elastic response. This range is characterized by a spontaneous total recovery of the sample after the stress release. Cold working techniques include cold drawing of films and fibers, rolling of thicker samples as well as other forging and pressing techniques (8, 9).