Studies on blends of a thermotropic liquid crystalline polymer with some thermoplastics

A totally aromatic thermotropic liquid crystalline polymer was melt blended in a twin–screw–extruder mainly with polyethylene terephtalate and polypropylene, and the blends were injection moulded into the form of standard test specimens. Mechanical properties of the blends were studied by tensile and impact tests and the blend morphology by scanning electron microscopy. Thermal expansion coefficients and heat deflection temperatures were also determined. The blends were two–phase systems, where LCP was as small spheres or fibres in the matrix. Skin–core morphology was found. LCP improved the mechanical properties as well as thermal and dimensional stability of the thermoplastics studied. Generally, the tensile strength, elastic modulus and HDT of the matrices increased with increasing LCP content, while elongation at break and Charpy impact strength decreased. This means that the blends were stiffer but also more brittle than the matrix polymers.