Random orientation of in situ composites based on liquid-crystalline polymers by compression moulding

In this study, randomly oriented in situ composites based on liquid-crystalline polymers (LCPs) were prepared by thermal compression moulding. The LCP employed was a semi-flexible liquid-crystalline copolyesteramide with 30 mol% of p-aminobenzoic acid (ABA) and 70mol% of poly(ethylene terephthalate) (PET). The matrices were poly(butylene terephthalate) (PBT) and polyamide 66 (PA66). The rheological properties, compatibility and morphological structures of these in situ composites were investigated. The results showed that PA66-LCP and PBT-LCP component pairs of the composites are miscible in the molten state, but partially compatible in the solid state. The ratios of viscosity, λ1 = ηLCP/ηPA66 and λ2 = ηLCP/ηPBT, are all greater than 1.0. However, the melt viscosity of the LCP/PBT and LCP/PA66 blend is much lower than that of PBT and PA66, and it decreases markedly with increasing LCP content. When the LCP/PA66 or LCP/PBT blends are compression moulded, the LCP/PA66 or LCP/PBT melts and flows easily due to their low viscosity, and the LCP phases in the melts deform easily along the flow directions, which are random. It leads to uniformly dispersed LCP micro-fibres randomly orientation in the thermoplastic matrix due to the compatibility between the blending components.