EVALUATION OF WELDLINE IN POLYCARBONATE BY LASER RAMAN SPECTROSCOPY

摘要

Molecular orientation in weldline region in injection molded polycarbonate was investigated by laser-Raman spectroscopy. The observation was focused, in particular, on the area surrounding a V-notch on the surface of weldline. In the case of opposite flow weldline occurring in moldings produced with a two-gated dog bone cavity, the molecules just on the V-notch were- slightly oriented along the notch, whereas those of the area within 1 mm from the V-notch were highly oriented parallel to the notch. Similar characteristics were found in an adjacent flow weldline occurring just behind an obstructive pin in a plaque mold. However, the degree of orientation varied along the weldline or flow direction. The degree of orientation was low near the obstacle and increased along the flow direction, resulting in high orientation in spite of complete disappearance of the V-notch at the area ca. 10 mm apart from the obstacle. In addition, further orientation was found in the position slightly apart from the disappeared V-notch. This suggested that the interface of the adjacent flow weldline behaved as a mold wall to generate shear flow during filling process.