EFFECTS OF SAMPLE GEOMETRY AND DRAW CONDITIONS ON THE MECHANICAL-PROPERTIES OF DRAWN POLY(ETHYLENE-TEREPHTHALATE)

Fibres and films prepared from solutions of high molecular weight poly(ethylene terephthalate) were drawn by two-stage drawing, tensile drawing or co-extrusion at low temperature (25-80°C) followed by tensile drawing at high temperature (230°C). Both fibres and films could be drawn up to a draw ratio of 11 by this method. The mechanical properties of drawn samples were greatly affected by the draw temperature for the first stage and the tension applied to the samples during cooling after the second-stage. The highest tensile modulus and strength for the drawn fibres that could be attained were 29.5 and 1.4 GPa, respectively, at the highest draw ratio of 11. For the films, the corresponding values were about half of those achieved for the fibres. The remarkable difference is closely related to the difference in amorphous chain orientation between drawn fibres and films, reflecting the different processing conditions available for each sample, and cross-sectional area. © 1990.