FLOW BEHAVIOR OF A THERMOTROPIC LIQUID CRYSTAL AROMATIC COPOLYESTER

Abstract

The rheology of a thermotropic aromatic copolyester, especially the steady shear viscosity, has been studied and found to be very different and more complex than that of analogous conventional isotropic polymers. The viscosity has a power-law dependence on shear rate over a wide range. The temperature dependence is very high below 300°C, and is comparable to that of isotropic polyesters above that temperature. The end correction measured by capillary viscometry is large, which is normally indicative of high melt elasticity, but nevertheless the extrudate swell is very small. The melt viscosity is shear and temperature history dependent. Unexplained effects that have been observed include dependence of viscosity upon apparatus gap dimensions and upon shear history.