Oxidative Degradation of Polymers. VI. Photooxidation of Polystyrene Powder and Some Model Compounds

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Abstract
The rates and products of photooxidation of polystyrene powder were studied at 70 °C under irradiation of a 30W low pressure mercury lamp. It was found that the rate of oxidation is remarkably high but the amount of oxygen incorporated into the polystyrene chain is very small. About a half of the absorbed oxygen appeared as carbon dioxide, independent of the conversion, irradiation time, oxygen pressure, and molecular weight. A trace amount of phenol was detected by GLC. The isotachophoretic analysis showed the formation of formic acid, oxalic acid, and glyoxylic acid. It was found that the mechanism of photooxidation is dependent on the state of the substrate, i.e., crystalline solid, melt(viscous liquid) or solution. It is concluded that the polystyrene powder is photooxidized from its surface and aromatic ring of polystyrene is cleaved to give carboxylic acids. It was suggested that ozone played an important role in the photooxidation of polystyrene. The conclusions are supported by the results obtained in the photooxidation of some model compouds such as 1,2-diphenylethane, hexamethylbenzene, azobenzene, and phenylazotriphenylmethane.

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