BIAXIAL HOT-DRAWING OF POLY(ETHYLENE-TEREPHTHALATE) - DEPENDENCE OF YIELD STRESS ON STRAIN-RATE RATIO

During a study of biaxial hot-drawing of amorphous poly(ethylene terep hthalate), the yield stress was determined in the temperature window b etween the glass transition and the rubber-like plateau, for various V alues of the strain-rate ratio, with one nominal strain-rate kept cons tant at 1 s(-1). Results were used to test predictions of the constitu tive model proposed earlier (Buckley, C. P. and Jones, D. C., Polymer 1995, 36, 3301), which expresses flow in terms of a three-dimensional generalisation of the Eyring rate process. Excellent agreement was obt ained for the variation of yield stress with strain-rate ratio. (C) 19 98 Elsevier Science Ltd. All rights reserved.