18O- time-of-flight secondary ion mass spectrometry technique to map the relative photooxidation resistance of automotive paint systems

Time-of-flight secondary ion mass spectroscopy has been used to image the O-18-labeled products formed in all coating layers when automotive paint systems are exposed to ultraviolet light and heat in an O-18(2) atmosphere. The O-18(-) ion intensity maps observed for model paint systems match the expected effects of ultraviolet light absorber additives, hindered amine light stabilizer additives, and pigments on photooxidation. The O-18(-) ion intensity maps observed for paint systems weathered in Florida for 3 years and then subsequently exposed to ultraviolet light for 1000 h in a 25% O-18(2) in dry nitrogen atmosphere correctly anticipate their long-term, >8 years, Florida exposure behavior, (C) 1999 Elsevier Science Ltd. All rights reserved.