Thermomechanical properties of a magnetically and mechanically oriented liquid crystalline copolyester, xydar

Elastic moduli and linear coefficients of thermal expansion (CTE) of a random thermotropic liquid crystalline copolyester, oriented in a magnetic field and by mechanical methods were measured in the directions parallel and perpendicular to the orientation direction. The axial elastic modulus of the magnetically oriented film was lower than that of the uniaxially stretched film. The elastic modulus measured in the transverse direction was higher for the magnetically oriented film. In the axial direction, both the mechanically stretched and magnetically oriented films exhibited shrinkage at low temperatures (CTE ≈ ‐2 · 10−5 K−1) and exhibited expansion at elevated temperatures. In the transverse direction, expansion was observed except for the biaxially stretched film at low temperatures. The magnetically oriented film showed the lowest axial CTE at elevated temperatures.