STRUCTURE AND MORPHOLOGY OF THE IN-SITU COMPOSITES OF A LIQUID-CRYSTALLINE POLYMER AND POLYCARBONATE

In situ composites were prepared via melt blending of a liquid crystal line polymer (LCP) and polycarbonate using a twin screw extruder, The structure and morphology of these composites were analysed using both transmission electron microscopy (TEM) and scanning electron microscop y. The LCP phases were able to orientate and form in situ submicrometr e fibres during the extrusion and postextrusion drawing. TEM images as well as selected-area diffraction patterns were obtained from the mat erials. The effects of both composition, i.e. LCP content, and postext rusion draw-down ratio on the development of the in situ formed LCP fi bres were studied in detail. A skin-core morphological differentiation is observed in these materials where well-defined LCP fibres of highe r aspect ratios were formed in the skin region. However, a significant amount of unelongated LCP particles were found coexisting with the le ss well-defined fibres in the core region of the extrudates, This skin -core differentiation was found to be dependent on the composition and the processing conditions, e.g. draw ratio. In this instance, electro n microscopy is proven to be a powerful technique not only for direct observation of the formation, dimensions and morphology of the in situ LCP fibres, but also for the qualitative and quantitative characteriz ation of the molecular orientation and crystalline structures in these fibres using selected-area electron diffraction. It is observed that the skin-core differentiation becomes more distinct in the in situ com posites containing a higher percentage of LCP but diminishes when the material is processed at higher post-extrusion draw ratio.