RHEOLOGICAL AND MECHANICAL-PROPERTIES OF LIQUID-CRYSTALLINE COPOLYESTER IN THE PRESENCE OF FILLERS OF VARIOUS NATURE

Rheological and physico-mechanical properties of LC copolyester on the base of PETP and p-hydroxybenzoic acid containing aerosil and talc have been studied. Features of the rheological behaviour of LC copolyester are related with structural changes of melts. Nonhomogeneous state of the material in the 240-260-degrees range is characterized by the high value of the flow activation energy, by the high value of viscosity, its weak dependence on the concentration of disperse fillers and the nonessential effect of the shear rate on the character of this dependence. Viscoplastic behavior (existence of the yield stress) of copolyester in these conditions is reinforced by the presence in the melt of the structural network with local crystallites in the lattice sites. The low values of viscosity, flow activation energy, the strong dependence of viscosity on the content of active small-disperse fillers above 260-degrees correspond to the nematic LC state. The applicability of the concentration-frequency reduction method for systems under study is shown for all the concentration-frequency range. An increase of the orientation of LC copolyester in the presence of small amount of a filler in the course of capillary flow is assumed resulting in decrease of viscosity of the system and increase of the modulus of elasticity of the composition.