| Abstract: | A series of thermotropic liquid crystalline polyesters based on p-acetoxybenzoic acid, naphthalene dicarboxylic acid, hydroquinone diacetate, and poly(ethylene terephthalate) were prepared via melt polycondensation. The anisotropic melts were studied by means of thermal optical testing, differential scanning calorimetry, scanning electron microscopy. X-ray diffraction, and rheological methods. It was found that the copolyesters in the mesomorphic state exhibit drastic shear-thinning and the experimental results indicate that the non-Newtonian Index n is in the range of 0.17 to 0.50, the flow-activation energies ΔEη are 297.1 to 182.0 KJ/mol over the shear rate of 10 to 1000 S?1 at temperature 225 to 270°C; and the mesomorphic copolymers are readily oriented during processing, resulting in highly oriented as-spun fibers. |
