Self-reinforced prepregs and laminates of a poly(phenylene oxide)—polystyrene alloy with a liquid crystalline polymer

Abstract

Extruded prepregs of a blend of a poly(phenylene oxide) (PPO)—polystyrene (PS) alloy with a liquid crystalline polymer (LCP) have been prepared for various concentrations and with different extension ratios. These prepregs have then been compression moulded into laminates with two orientations of the prepregs in the laminate. In one case, 16 prepreg sheets have been placed in unidirectional orientation. In the other, the 16 sheets have been placed in such a way that each subsequent sheet was at a 45° angle with respect to the preceding sheet, thereby yielding a quasi-isotropic orientation. The laminates have been prepared for each extension ratio with different reduction ratios. The unidirectional 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 properties. The mechanical properties of the laminates have been compared to the values obtained for injection moulded blends of the same materials. Prediction of the mechanical properties of the quasi-isotropic laminates have been carried out based on the values obtained for the unidirectional 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 than those obtained for the injection moulded blends of the same concentration tested in the machine direction. The morphologies of the prepreg sheets with various extension ratios have been studied in order to determine 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 novel processing technique enables the preparation of self-reinforced laminates of LCP—thermoplastic blends, with controlled anisotropy and enhanced mechanical properties, when compared with the corresponding injection moulded blends.