MEASUREMENT OF MOLECULAR ORIENTATION IN INJECTION-MOLDED POLYPROPYLENE BY MICRO-RAMAN SPECTROSCOPY

The micron-scale distribution of molecular orientation in the cross section of an injection-molded polypropylene sheet was determined by polarized micro-Raman spectroscopy. The intensity ratio of 808 cm(-1) band to 841 cm(-1) band in polarized Raman spectrum of polypropylene was found to be a good index of molecular orientation. By focusing the laser beam to approximately 2 mu m, next results were obtained. (1) The depth profile of the intensity ratio near the center of the sheet showed the multilayer structure of molecular orientation at positions of about 100 and 350 mu m from the surface. (2) The depth profiles of the direction and degree of orientation near the film gate were simultaneously obtained and showed that the disorder of the flow existed to about 2 mm distance from the gate.