Control of High-order Structure of Poly(ethylene terephthalate) Fibers by Blending with Liquid Crystalline Polymer

Abstract

Poly(ethylene terephthalate) (PET) fibers blended with a small amount of liquid crystalline polymer (LCP) were prepared by melt spinning at take-up velocities of 0.5, 2 and 4 km/min. Structure and properties of the fibers were analyzed by measurements of wide-angle X-ray diffraction, birefringence, modulated differential scanning calorimetry, scanning electron microscopy and mechanical properties. The experimental results clearly showed that the blending with LCP had no significant effect on the high-order structure of PET fibers at low take-up velocities, whereas molecular orientation and orientation-induced crystallization were significantly suppressed at high velocities. Mixing conditions also affected the structure development of PET component, in that the increase in the revolution of screw resulted in the decrease of the effect of LCP for suppressing the orientation-induced crystallization. In the drawing of as-spun PET/LCP blend fibers, high drawing temperatures prevented the breakage of the fibers at high draw ratios and led to the preparation of drawn fibers with high tensile modulus and strength of 123 cN/dtex (17GPa) and 9.4 cN/dtex (1.3 GPa), respectively.