Miscibility and morphology of poly p-phenylene sulphide–liquid crystal polymer blends

Blends of poly p-phenylene sulphide (PPS) and a liquid crystalline polymer (LCP) were made by two methods: (i) mixing and capillary extrusion (samples A), and (ii) injection moulding (samples B). To study miscibility in the melt and solid states and the resulting morphology, techniques like polarized light optical microscopy, capillary rheometry, dynamic mechanical thermal analysis and scanning electron microscopy with X-ray microanalysis were used. It was observed that the miscibility of the amorphous fractions of both polymers increased with increasing intensity (rates and stresses) of deformational flow (shear and elongational). Samples A had a morphology composed of fibrils of both polymers, but a matrix made of only one polymer i.e. PPS. Samples B had a mainly fibrillar morphology, with no observable matrix, made of both polymers. Formation of pure LCP fibrils was not observed neither in the extruded blends nor in the injection moulded samples. The addition of LCP to PPS improved its mechanical properties. At a molecular level, these blends can be considered to be “molecular composites”.