Determination of ultraviolet light absorber longevity and distribution in automotive paint systems using ultraviolet micro-spectroscopy

Ultraviolet light absorber additives (UVAs) are added to the basecoat and c learcoat layers of modern, multi-layer, automotive paint systems in order t o protect the clearcoat and screen the underlying layers from harmful UV li ght. Unfortunately, these UVAs are subject to photodegradation resulting in diminished UV protection as a paint system weathers. This paper describes an ultraviolet micro-spectroscopic technique that has been developed to mea sure ultraviolet light absorber content, location, and longevity in the cle arcoat layer of complete, intact, automotive, paint systems. Three automoti ve paint systems containing different UVAs were examined initially and afte r exposure in Florida. UVA content and distribution were determined in each of the paint systems with weathering and the longevity was determined. Thi s work demonstrates an accurate, unambiguous technique for quantifying UVA loss in coatings. (C) 2001 Elsevier Science Ltd. All rights reserved.