Generation of internal stress in the process of solidification of synthetic resin, III : research of molecular structure change related to internal stress by infrared absorption spectrum

Abstract

The changes of molecular structures owing to the solidification by casting epoxy resin, and also owing to the solidification by injection molding of polystyrene copolymer were studied with infrared spectrum. Epoxy resin, with cis-cyclohexane-dicarboxylic acid anhydride hardener, firstly seems to be esterified through the opening of epoxy ring and combining with the acid anhydride, and finally to form a net work structure by di-ester and ether formation. This net work formation seems to be related with the generation of the internal stress when restrained. On the other hand, the polarized infrared spectrum of injection molded polystyrene copolymer shows that molecules orientate themselves by rapid cooling of molten flow under high shearing force, as in stretched film, and by heating an injection molded specimen the orientation diminishes and deformation occurs, and this orientation corresponds to the internal stress in the linear polymer.