RHEOLOGICAL AND MECHANICAL-PROPERTIES OF ANTIPLASTICIZED AND RUBBER-TOUGHENED BISPHENOL-A POLYCARBONATE

The addition of a high-T-g aromatic diluent to bisphenol A polycarbonate (PC) reduced T-g and melt viscosity while raising elastic modulus and yield stress substantially. Ultimate tensile elongation and impact toughness were badly affected. However, the addition to these antiplasticized blends of a small amount of a rubber modifier restored impact toughness and elongation but left the blend with increased melt fluidity and ambient stiffness re: neat PC. The key to this rebalancing of the properties of PC was found to be the disappearance of the plane strain crack instability that is a hallmark of the neat resin. The deformation mechanism in all the rubber-containing blends in all failure tests, regardless of geometric constraint and strain rate was found to be shear flow alone. The large plastic zone seen at the plane strain crack tip appears to involve rubber particle cavitation as well. (C) 1995 John Wiley & Sons, Inc.