RHEOLOGICAL BEHAVIORS OF BISPHENOL SERIES THERMOTROPIC LIQUID-CRYSTALLINE WHOLLY AROMATIC COPOLYESTERS

Rheological experiments were performed on a series of thermotropic liq uid crystalline aromatic copolyesters based on terephthalic acid (TPA) , isophthalic acid (IPA), p-hydroxybenzoic acid (HBA), and a family of bisphenols. The anisotropic melts behaved as non-Newtonian fluids in a shear elongation flow. The non-Newtonian exponents of the melts decr eased with increasing the linearity of the bisphenol bridge group, and decreased with increasing the optical anisotropy in the liquid crysta lline phase. The cross-section morphologies along the longitudinal dir ection of the extrudates were surveyed by scanning electronic microsco py (SEM) and discussed with melt-flow rate distributions. The extrudat es exhibited skin-core microstructures and oriented fibril structures. The die swells of the extrudates decreased sharply to negligible leve ls when shear stress was above 1000 Pa. (C) 1993 John Wiley & Sons, In c.