Detailed Investigations of Structural Layering Phenomena in Injection Molded Thermotropic Liquid Crystalline Polymers

Abstract

Abstract The structural gradients developed in the injection molding of thermotropic wholly aromatic copolyester parts were characterized using a specially developed micro-beam wide angle X-ray diffraction camera technique and wide angle X-ray pole figure analysis techniques. Wide angle X-ray pole figure analyses indicate that the local macro-symmetry throughout the sample seems to he uniaxial. The polymer chains are generally oriented in the flow direction except in the core regions after the diverging section, where molecular chains tended to orient transversely to the flow direction. The local orientation of chains is determined from the micro-WAXS film patterns using DIA (Digital Image Analysis) technique. This enabled us to map the orientation of the local symmetry axes as well as local chain orientation through the thickness direction. The data indicate that the chain orientation is highest at the skin layer, becomes lower at the sub-skin layer, then increases gradually toward the shear layer and finally decreases to very low levels in the core regions.