A study of molecular orientation in injection-molded polycarbonate by laser-Raman spectroscopy.

概要

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To clarify the formation process of frozen molecular orientation in the mold cavity during the molding process of injection-molded polycarbonate (PC) disk, we applied the polarized laser-Raman spectroscopy. The intensity ratio for 635 cm-1 and 703 cm-1 peaks in a Raman spectrum of PC varies with the degree of the frozen molecular orientation formed by the back-flowing of the polymer melt from the mold cavity during the holding process. We took up the relative intensity ratio, 1 (635cm-1/I) (703cm-1) to estimate the frozen molecular orientation distribution along the disk cross-section perpendicular to the flow direction. The frozen molecular orientation consists of three zones; a skin layer, a shear zone, and a core layer. The skin layer, which is in contact with the mold cavity, consists of non-oriented molecules, because its cooling rate is very high. The core layer consists of molecules whose orientation is considerably relaxed, because its cooling rate is lowest. The shear zone between the skin layer and the core layer consists of highly oriented molecules, caused by large shear stresses during the cooling process.
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