Tensile drawing behaviour of poly(ethylene terephthalate)

Abstract

A detailed study has been undertaken of the drawing behaviour of poly(ethylene terephthalate) over the temperature range 20° to 80°C. Cold drawing behaviour was observed at the lower temperatures and homogeneous deformation at 80°C. Samples were also subjected to two-stage drawing: homogeneous draw at 80°C followed by cold drawing at 20°C. In all cases the geometry of the deformation was monitored by measuring the changes in macroscopic dimensions. In addition, measurements were made of the final birefringence, and the shrinkage force developed when the drawn samples were heated to a temperature above T g . The results are discussed in terms of continuum models for the deformation of polymers. In particular, the relevance of a simple molecular network model is considered. It is shown that many of the observations are consistent with the deformation of a molecular network, although our understanding of the molecular processes involved in cold drawing is still incomplete.