SELF-REINFORCED PREPREGS AND LAMINATES OF A POLY(PHENYLENE OXIDE)-POLYSTYRENE ALLOY WITH A LIQUID-CRYSTALLINE POLYMER

Extruded prepregs of a blend of a poly(phenylene oxide) (PPO)-polystyr ene (PS) alloy with a liquid crystalline polymer (LCP) have been prepa red for various concentrations and with different extension ratios. Th ese prepregs have then been compression moulded into laminates with tw o orientations of the prepregs in the laminate. In one case, 16 prepre g sheets have been placed in unidirectional orientation. In the other, the 16 sheets have been placed in such a way that each subsequent she et was at a 45 degrees angle with respect to the preceding sheet, ther eby yielding a quasi-isotropic orientation. The laminates have been pr epared for each extension ratio with different reduction ratios. The u nidirectional laminates have been tested for the tensile strength and secant modulus in the machine direction and the transverse direction. The quasi-isotropic laminates have also been tested for mechanical pro perties. The mechanical properties of the laminates have been compared to the values obtained for injection moulded blends of the same mater ials. Prediction of the mechanical properties of the quasi-isotropic l aminates have been carried out based on the values obtained for the un idirectional laminates tested in the machine and transverse directions . The mechanical properties of the quasi-isotropic laminates with high extension and reduction ratios are either comparable to or higher tha n those obtained for the injection moulded blends of the same concentr ation tested in the machine direction. The morphologies of the prepreg sheets with various extension ratios have been studied in order to de termine the nature of the LCP fibres in the prepregs. The morphologies of the quasi-isotropic laminates with various LCP concentrations have also been studied in order to determine the effect of orientation of the LCP fibres in the laminates. The studies have shown that this nove l processing technique enables the preparation of self-reinforced lami nates of LCP-thermoplastic blends, with controlled anisotropy and enha nced mechanical properties, when compared with the corresponding injec tion moulded blends.