Thermo-mechanical properties of liquid crystalline copolyesters

The thermo-mechanical behavior of an all-aromatic liquid crystalline copolyester, Thermx(R) LCP, is compared to the behavior of several other commercial LCPs. The effect of orientation in both injection moldings and fibers is assessed from the deflection temperature under load or DTUL, dynamic mechanical modulus, and creep compliance. The DTUL is dependent not only on stiffness, but also on thermal expansion and creep behavior. The DTUL is defined here so that the significance of injection molding specimen thickness may be determined. By measuring the dynamical mechanical properties during the deflection-under-load test, a determination of the creep behavior can be made. These materials exhibit different creep tendencies, as was confirmed by creep compliance measurements at elevated temperatures.