| Abstract: | Self-reinforced sheets (prepregs) have been prepared by stretching extruded sheets made of thermoplastic (TP) and a thermotropic liquid crystalline polymer (LCP) blend. The sheets are formed by extrusion through a coathanger die, device. Processing at this stage is done at a temperature at which both components in the blend are melt processable. These prepregs are laid up in multi-layers in a direction parallel to the stretching direction or in the direction of 45° with respect to each previous layer. The lay-ups are compression molded into unidirectional or isotropic laminates at temperatures below the melt processing temperature of the LCP. Various pairs of TP and LCP have been studied. These include polypropylene and an LCP based on p-oxybenzoyl, terephthaloyl and hydroquinone moieties, polyphenylene oxide (PPO) and polystyrene/PPO alloy and a LCP based on 6-oxy-2-naphthoyl and p-oxybenzoyl moieties. Mechanical properties of the prepregs and laminates were measured and compared with those obtained from injection molded samples. Surprisingly, tensile strength and modulus of isotropic laminates are found to be higher than those of injection molded samples in the flow direction. Morphlogical studies of the prepregs and laminates indicate the presence of well-defined LCP fibers in various thermoplastic matrices. |
