The molecular reorganization occurring in liquid crystalline polymer fiber during heat treatment is of great interest for
many commercial reasons. Using thermal analysis techniques, WAXS and real time temperature dependent synchrotron SAXS, the
structure and morphology of commercial LCP (liquid crystalline polymer), Vectran®, HBA/HNA (p-hydroxybenzoic acid/6-hydroxy-2-naphthoic acid), and its variant polymer fiber COTBP, HBA/HNA/BP/TA (BP-benzophenone, TA-terephthalic
acid), have been examined. Both fibers have the typical liquid crystalline polymer structure, i.e., highly aligned with aperiodic
sequencing along the fiber axis. There is a three-fold increase in strength in both fibers with heat treatment; however, the
modulus is observed to increase significantly in COTBP but not in Vectran®.
This paper reports on the changes and the differences on the structural and morphological behavior for both the as-spun and
heat-treated LCP fibers. We propose an ‘oriented entanglement’ model to describe the differences between the two polymer fibers.