The photo-oxidation of polyolefins containing a hindered piperidine compound

The rate of oxygen absorption by unstabilised PE and PP, as well as by the same polymers stabilised with bis-(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (Tinuvin 770), has been determined during photo-oxidation at several temperatures and uv light intensities. In addition, the rate of stabiliser conversion has been measured under various irradiation conditions, including outdoor exposure. The activation energy of the conversion of Tinuvin 770 appears to be much less than that of the photo-oxidation of PE. When stabilised with 0·1% Tinuvin 770, PE and PP differ with respect to the dependence on light intensity of their rates of oxygen uptake. The consequences of these results for the interpretation of accelerated ageing tests are discussed.