FT-IR analysis of the photooxidation of styrene-acrylonitrile copolymers

Abstract

Infrared spectroscopy was used to study the photooxidation of the styrene-acrylonitrile (SAN) copolymer samples that were exposed to ultraviolet radiation having a minimum wavelength of 290 nm. It was determined that the photooxidation of SAN occurs exclusively at the styrene repeat units within the copolymer structure. The major infrared spectral changes resulting from the degradation process involve the appearance of new peaks within the hydroxyl and carbonyl regions. Using factor analysis results, it was concluded that there are a minimum of four different types of hydroxyl groups and three different types of carbonyl groups formed during the photooxidation of SAN. Furthermore, it was found that after 200 h exposure the rate of increase in the concentration of the carbonyl groups within the degraded material is greater than the rate of increase in the concentration of the hydroxyl groups.