Formation of Novel Thermoplastic Composites from Liquid Crystalline Polymers andTheir Blends

摘要

The miscibility of several liquid crystalline polymers (LCPs) blended withpolyetherimide (PEI) was found to have a significant effect on the mechanical properties of the blend. Although the properties are higher than the matrix PEI, it has been found that immiscible blends of PEI with some LCPs show a negative deviation from the law of mixtures for flexural properties and tensile properties. In contrast, other LCPs which are partially miscible with PEI show a positive deviation from this law. The partial miscibility is probably responsible for the synergistic enhancement of some of the physical properties. Additionally, the LCP reinforcement was found to substantially lower the torsional creep compliance of the blend and blending with PEI increases the thermoformability of some of the LCPs. The reinforcing LCP fibrils and their molecular orientation were retained in the blends when thermoformed above the melting point of the LCPs. Secondly, a mixing process was developed which would generate continuous LCP fibrils in the matrix polymer during processing and allow blending of polymers such as LCPs with other matrices, which usually do not have overlapping processing temperatures, such as polypropylene and poly(ethylene terepthalate). The blending process allows us to impart separate thermal histories to the matrix and the LCP to yield a favorable viscosity ratio. The tensile moduli of the blends made by this approach had significantly improved properties than physical blends.