Long-term behaviour of oil-based varnishes and paints 4. Influence of filmthickness on the photooxidation

Photooxidation of dried linseed oil films with various thicknesses is analy sed. Distributions of the photoproducts resulting from photooxidation are d etermined by photoacoustic IR spectrometry and by micro-IR spectrometry. Ox idation profiles are observed and it is shown that oxidation can extend up to 300 mum. This result is confirmed by micro-fluorescence analysis of the photo-oxidized sample. On the other hand, the cross-sectional analysis of t he exposed films suggest that crosslinking occurs in the oxidized layers, w hich could prevent some of the low molecular weight products formed from mi grating from the solid film towards the surrounding atmosphere. (C) 2001 El sevier Science Ltd. All rights reserved.