ORIENTATION PROFILES IN THE STRAND OF THERMOTROPIC LIQUID-CRYSTALLINE POLYMER STUDIED BY POLARIZED FOURIER-TRANSFORM INFRARED MICROSPECTROSCOPY

The orientation profiles in extrusion-molded strands of a thermotropic liquid-crystalline polyester were obtained by Fourier transform infrared (FTIR) microspectroscopy. The polarized infrared spectra were measured in microscopic area down to 40-mu-m as a function of distance from the centers of the strands. The orientation profiles are discussed in relation to the morphological structure studied by polarized optical microscopy and scanning electron microscopy (SEM). In the case of the strand 1.52 mm thick, the microscopic orientation function is lower in the central region of the strand but increases markedly toward the surface of the strand. The core region of the thicker strand exhibits curved band patterns in polarized optical micrography and scanning electron micrographs. With decreasing strand diameter, the microscopic orientation function varies more gradually with the radial position and the orientation function in the central region is much improved. The fracture surface of thinner strands does not show a band pattern but exhibits highly oriented fibrillar morphology.