Polymer Engineering and Science, Vol.35, No.1, 52-63, 1995
Influence of Processing History on the Properties of a Thermotropic Copolyester Polycarbonate Blend
Relationships between the rheological, morphological, and tensile properties of an immiscible blend of 25 wt% of a thermotropic liquid crystalline polymer (LCP) with polycarbonate are presented. The shear viscosity of the blend is intermediate between the two constituent materials, and indicates immiscibility in the melt. Extrudate swell behavior is examined and found to be closely related to that of polycarbonate. The morphology of the dispersed LCP phase varies between droplets and oriented fibrils, and is highly correlated with changes in tensile properties. Fibrils are associated with increased tensile modulus, and their development is favored in the elongation flow fields present in the spinline and in the die convergence section. In all cases, blend stiffness is less than that predicted for a continuous fiber-reinforced composite. Enhanced tensile modulus is associated with both extrusion from shorter length dies and increases in spinline draw ratio, with the latter proving the most important in fibril formation.
Keywords:LIQUID-CRYSTALLINE POLYMERS;POLYCARBONATE BLENDS;MECHANICAL-PROPERTIES;HYDROXYBENZOIC ACID;MORPHOLOGY;FLOW;COPOLYESTER;FIBRILLATION;DEFORMATION;POLYSTYRENE