The effect of UV light on the subsequent thermal volatilization of poly(methyl acrylate)

Abstract

AbstractFilms of poly(methyl acrylate) were exposed to UV light for periods of up to 45 min and were then degraded thermally under vacuum and at atmospheric pressure in nitrogen. Short exposures caused a marked decrease in the initial rate of thermolysis, and this was attributed to the removal of active centers. The formation of crosslinks during photolysis severely decreased the subsequent rate of volatilization of the polymer by inhibiting the unbuttoning chain reaction mechanism. Volatilization of exposed films under vacuum was slower than at atmospheric pressure in nitrogen, and this was attributed to the loss by evaporation of active centers. Activation energies for thermolysis before and after UV exposure were 160 and 167 kJ/mole, respectively. The subsequent thermal behavior of films exposed to UV light in oxygen and nitrogen atmospheres was closely similar.