On the dynamic mechanical behaviour of drawn poly(ethylene terephthalate) fibers

Abstract

The effect of drawing and annealing treatments on the α transition in poly(ethylene terephthalate), PET, yarns has been studied using a combination of X-ray and dynamic mechanical techniques. It was found that drawn, crystalline PET yarns exhibit a shift in the position of the α transition to lower temperatures for high annealing temperatures; this effect has been observed for unoriented, crystalline PET. The main difference between the results for the drawn and unoriented yarns lies in the position of the α transition on the temperature scale; the α transition occurs at higher temperatures the higher the draw ratio. The shift in the position of the α transition with anealing is interpreted in terms of the number of crystals whilst the change in position of the α transition brought about by drawing is explained by orientation in the amorphous regions.