Mechanical Behavior of Rigid Rod Polymeric Fibers

Abstract

ABSTRACTPoly-(p-phenylene benzobisthiazole) fibers provide a model system for the evaluation of structure-property relationships in extended-chain polymeric fibers. Owing to the poorly developed lateral order in as-spun fibers, the enhancement of structural perfection and of mechanical properties may be examined through heat treatment processing more readily than with more crystalline fibers. High tensile modulus (to 300 GPa) and high tensile strength (3 GPa) have been obtained from heat treatment processing of the fibers. The development of tensile modulus and tensile strength depends directly on the enhancement of overall axial molecular orientation. Tensile strength is additionally dominated by the development of stronger lateral molecular interaction. The mechanical properties mimic the inherent chain anisotropy arising from strong primary bonding along the chain and much weaker secondary interactions between chains. Tensile to shear moduli ratios of 200:1, tensile to shear strength ratios of 50:1 and tensile to compressive strength ratios of 10:1 are observed.