The mechanism of oxidative degradation of ABS resin. Part II. The mechanism of photooxidative degradation

The mechanism of oxidative degradation of ABS resin under ultraviolet irradiation, especially with respect to the wavelength dependencies of the photooxidative rate, has been examined by a spectroweather tester and infrared spectroscopy. The irradiation wave region was 290–800 mμ, and the region was divided into six parts. The changes in each part were examined by infrared spectroscopy. The absorption bands belonging to nitrile and phenyl groups showed no changes, but bands belonging to carbonyl and hydroxyl groups changed markedly, much as in the thermooxidative degradation described in a previous paper. There was a distinct gap between the third and fourth regions, which corresponded to 350 mμ. The graph of the normalized absorbance ratio and the logarithm of the wavelength gave a straight line, and it indicated that the rate of oxidation is proportional to the light intensity and the logarithm of the wavenumber.