Study of degradation of polystyrene by means of mass spectrometry

The degradation of polystyrene by heat and ultraviolet radiant energy was followed by mass spectrometric analysis of the gaseous products evolved. Oxygen content, discoloration, and insolubility of the treated polymer were also investigated. The degradation of polystyrene involves two different processes: (1) the breakdown of thermolabile groups formed in the polymer prior to degradative treatment; this breakdown is caused by exposure to heat at 120°C. in vacuo and 115°C. in oxygen and to ultraviolet radiant energy at 120°C. in vacuo and 118°C. in oxygen; it is accompanied by the removal of residual materials such as solvent; and (2) the oxidation of the polymer caused by exposure to ultraviolet radiant energy in the presence of oxygen. The evolution of benzene, methyl ethyl ketone, dimethylbenzenes, and alcohols is associated with the first stage involving the breakdown of thermolabile groups and the removal of residual materials. Compounds such as formaldehyde, formic acid, and acetic acid are produced as a result of oxidation of the polymer. The oxygen content of the polymer was decreased from 0.33 to approximately 0.1 percent by heating at 120°C. in vacuo and at 115°C. in oxygen, and by exposure to ultraviolet radiant energy at 120°C. in vacuo . Ultraviolet treatment at 118°C. in oxygen for 250 hours quadrupled the original oxygen concentration. Discoloration of the polystyrene was definitely noted only on exposure to ultraviolet radiant energy in oxygen and is associated with oxidation of the polymer. The material became insoluble as a result of all heat and ultraviolet treatments. The amount of insoluble material increased with severity of exposure conditions.