Study on the Structure and the Tensile Property of a 60 mol % p-Hydroxybenzoic Acid/40 mol % Ethylene Terephthalate Liquid Crystalline Copolyester Oriented in a Magnetic Field

A thermotropic liquid crystalline copolyester, one from the Rodrun series, consisting of 60 mol % p -hydroxybenzoic acid and 40 mol % ethylene terephthalate was aligned under a magnetic field of 6 T and by mechanical methods. The tensile properties of the aligned films were different depending on the orientation degree and the means used for the orientation. The magnetically oriented films exhibited a lower ultimate tensile strength than the mechanically oriented films, but their elastic modulus was as high as that of the mechanically oriented films, suggesting that magnetic fields could provide an additional means for orientation in processing thermotropic liquid crystalline copolyesters. The difference in tensile properties was discussed in relation to the oriented structures examined by wide-angle X-ray measurement, the high-resolution solid-state 13 C NMR technique, Fourier transform infrared spectroscopy, and polarizing microscopy.