Studies of blends containing liquid crystalline polymers with PET and related investigations of hydroquinone/biphenol polysulfone systems

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Virginia Polytechnic Institute and State University

The investigation of structure-property behavior of extruded cast films prepared from blends of thermotropic liquid crystalline copolyesters with polyethylene terephthalate (PET). Data were obtained which showed not only the temperature dependence of the moduli and stress-strain behavior but also the orientation effects that must be prevalent in order to explain the differences between the moduli measured parallel and perpendicular to the extrusion direction. Only at high liquid crystal polymer (LCP) compositions is the modulus particularly increased. The modulus enhancement with lower LCP content and utilization of process variables are discussed. Specifically, the extruder gear pump speed did not enhance Young's modulus at the same LCP content as extensively as did the effect of extruder screw speed. Also a study to synthesize and characterize new segmented copolymers that could produce unusual film properties are discussed. The approach involved the synthesis of high Tg (220 C) isotropic poly (aryl ether sulfone) oligomers of varying segment molecular weights. The thermal and mechanical studies of the copolymers have been carried out to probe the potential of these copolymers for signs of liquid crystalline character and to note their ability to thermally crystallize as well as to crystallize by solvent or strain inducement. Along these lines, thermal analysis, polarizing hot-stage microscopy, wide angle x-ray scattering and mechanical testing were utilized in this investigation