Rheological behaviors of bisphenol series thermotropic liquid crystalline wholly aromatic copolyesters

Abstract

AbstractRheological experiments were performed on a series of thermotropic liquid 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 decreased with increasing the linearity of the bisphenol bridge group, and decreased with increasing the optical anisotropy in the liquid crystalline phase. The cross‐section morphologies along the longitudinal direction of the extrudates were surveyed by scanning electronic microscopy (SEM) and discussed with melt‐flow rate distributions. The extrudates exhibited skin–core microstructures and oriented fibril structures. The die swells of the extrudates decreased sharply to negligible levels when shear stress was above 1000 Pa. © 1993 John Wiley & Sons, Inc.