Features of flow curves of lc-copolyesters and structural-mechanical parameters of extrudates received in different phase states of the melt
Соpolyesters on the basis of poly(ethylene terephthalate) and acetoxybenzoic acids above melt temperature are found out by two phase regions: low-temperature region, where in nematic to a phase are present high-melting crystallites, and high-temperature region, where it is formed homogeneous nematic melt. For heterophase melt anomaly of flow curves and the time instability of shear viscosity caused by development of processes of crystallisation and a disorientation of structural elements is characteristic. Viscosity of homogeneous melts does not depend on time and flowability diagrams liquid-crystal melts have a usual appearance for thermoplastics with an insignificant deviation from Newtonian flow regime. Extrudates received from homogeneous melt, have essentially higher values of molecular orientation and strength in comparison with extrudates formed of heterophase melt.