The mechanism of oxidative degradation of ABS resin. Part I. The mechanism of thermooxidative degradation

Abstract In this work the early stages of the thermal oxidation of ABS resin films for commercial utilization and purified samples were studied by means of infrared spectroscopy. The film samples were submitted to thermal oxidation in a Gear oven at 70–90°C. During the aging in the Gear oven the nitrile and phenyl absorbance did not change, but oxidative products containing hydroxyl or carbonyl groups were produced rapidly, and the butadiene content decreased gradually. Two parts of the oxidative reaction were easily distinguished by analysis of the degradation procedure in the differential method and in the half‐time method. An activation energy of 10 kcal./mole or less was obtained for the initiation process, involving mainly the formation of hydroperoxides induced by radical formation, which was apparent in the commercial samples, whereas a value of 10–20 kcal./mole was obtained for the subsequent process, initiated by the decomposition of the hydroperoxides, which induces chain‐carrier reactions. A reaction scheme is proposed, and kinetic expressions are developed therefrom. These expressions explain the experimental results very well.