Exposure response function for a quantitative prediction of weathering caused aging of polyethylene

The exposure response function of the carbonyl formation over the bulk has been determined for a high-density polyethylene of a thickness of 200 gm, which was used as a weathering reference material according to ISO TR 19032. To this end, spectral sensitivity was studied by local measurement of the effect of spectrally dispersed irradiation. Both the exposure device and the methodology of determination are described. The temperature dependency of photooxidation was determined by UV exposure at various temperatures between 23 and 80 degrees C. Deviations from linearity and thus reciprocity below 40 degrees C are discussed and assumed to be related to diffusion limitations. An Arrhenius approach-based on data of linear carbonyl formation - has been incorporated into the exposure response function. Using this exposure response function, aging in terms of the distribution of a quantitative property change over a plastic component can be predicted for a specific outdoor location with real chronologic weather data as input for the exposure. Thus, artificial and natural weathering can be linked and compared. The established exposure response function has been validated by outdoor exposure results from the literature. If an estimated diffusion limitation is taken into consideration, calculations and published data are in good agreement.