Visualisation and characterisation of ageing induced changes of polymeric surfaces by spectroscopic imaging methods

A polymeric resin material was chosen as the model system to visualise the ageing-induced chemical surface changes with molecular spectroscopic imaging techniques and correlate these results to physical properties such as colour changes. The influence of light radiation, temperature and humidity on the polymeric surfaces was analysed by means of attenuated total reflection infrared imaging, Raman imaging spectroscopy and scanning electron microscopy. Samples were analysed before, during and after the weathering/ageing tests. From these combined data, the mechanisms for the damaging of the resin surface under the various environmental conditions (as applied in the accelerated ageing tests) were deduced. Photo-oxidative decay of the resin leading to a degradation of the uppermost surface layers as well as hydrolysis of the aged surface was identified. The combination of the spectral and spatial data as obtained from spectroscopic imaging with the morphological and elemental information of scanning electron microscopic mapping experiments turned out to be highly advantageous for the elucidation of ageing processes. A correlation between the molecular spectroscopic data and the results from the macroscopic colour difference measurements was found.