Rheology of melts of a model low-melting liquid crystalline copolymer of bis (4-chlorocarbonylphenyl) terephthalate with polypropylene glycol. Plastic flow and non-linear viscoelasticity

Abstract

The dependence of viscosity on shear rate and of the Young modulus on frequency were measured for low-melting, thermotropic polyester — a copolymer of bis (chlorocarbonylphenyl) terephthalate and polypropylene glycol. In the temperature interval 120–180°C, where the copolymer exists in the liquid-crystalline state, it behaves as a pseudoplastic body. Above 230°C the copolymer melt becomes isotropic. In the region between 180 and 230°C its properties are not stable, probably due to a coexistence of smectic, nematic, and isotropic domains. When the polyester in the liquid-crystalline state undergoes dynamic deformation, its viscoelastic behaviour is non-linear.