PROCESSING, MORPHOLOGY AND PROPERTIES OF A THERMOTROPIC LIQUID-CRYSTALLINE POLYMER

The relationship between processing parameters, morphology and properties has been investigate for injection mouldings and extrudates of filled and unfilled grades of a thermotropic copolyester. Low injection speeds were found to result in a significant increase in tensile strength and modulus in the flow direction. This was correlated with an increase in the thickness of the highly oriented skin layer and also with improved molecular orientation of the core regions. Tensile tests on single layers confirmed the skin to have a higher tensile strength and modulus than the core, and the tensile properties to correlate well with the local orientation. With the addition of mineral filler, the influence of injection speed on tensile properties became less marked, and the properties within the mouldings were more homogeneous. The adhesion between the layers also improved in the presence of filler. Additional tests were carried out on extruded tubes. The extensional flows associated with the extrusion process lead to relatively high molecular orientation in the extrusion direction and therefore to good mechanical properties.