EVALUATION OF MOLECULAR ORIENTATION OF WELDLINE REGION IN POLYCARBONATE BY LASER RAMAN SPECTROSCOPY

摘要

Molecular orientation in weldline region in injection molded polycarbonate was investigated by polarized laser-Raman spectroscopy. The relative intensity ratio of two specific peaks in a spectrum was determined as an index of molecular orientation in accordance with an earlier report. The intensity ratio of the peaks showed the highest value at the point ca. 30 μm apart from the V-notch at the surface of the specimen. The orientation direction was found to be parallel to the weldline. The birefringence, Δn, of this point was estimated to be 2.64×10~(-3) from the results of another study to determine the relationship between Raman peak intensity and birefringence. This value corresponded to ca. 2.5 % of the intrinsic birefringence of polycarbonate, 0.106. Meanwhile, the birefringence of V-notch itself was calculated to be 0.59×10~(-3), lower than that of the surroundings. Although a similar tendency was found at the area ca. 100 μm inside from the surface, the birefringence itself was slightly lower than that of the surface. These results suggest that molecular orientation increases near the weldline due to convergent flow, while the molecules at the interface of the weldline relax. Thus laser-Raman spectroscopy provides some important clues to understand the flow behavior around weldline.