Effects of the heat treatment on the mechanical properties of a novel thermotropic liquid-crystalline polymer fiber

Abstract

Thermotropic liquid-crystalline polymers (TLCPs) have aroused wide public concern which is attributed to their high strength, stiffness, chemical resistance and perfect dimensional stability as high-performance engineering materials. Vectran heat treated after melt spinning is a representative commercial aromatic copolyester fiber. In this study, a novel TLCP melt-polymerized with 4,4'-diphenyloxide dicarboxylic acid (DODA), 4-acetoxybenzoic acid (ABA), hydroquinone diactate (HQA), 2,6-naphthalene dicarboxylic (NDA) and terephthalic acid (TA) were melt spun into fibers and heat treated to enhance the breaking strength and Young's modulus. Intermolecular mechanical elements slipped between 120-130 °C and crystallization or the conformational rotations occurred along the extended polymer chain. For this new TLCP fiber, the optimal heat treatment temperature was 260 °C and the suitable heat-treatment time was over 48 hours. The breaking strength, Young's modulus and breaking elongation of the as-spun fiber were improved from 1.58GPa, 45.21GPa and 1.97% to 3.20GPa, 133.44GPa and 2.42% respectively after heat treatment. © (2012) Trans Tech Publications, Switzerland.