USE OF CHEMILUMINESCENCE TO THE STUDY OF PHOTOSTABILITY OF AUTOMOTIVECOATINGS

Chemiluminescence (CL) imaging has been used to study the photodegrada tion of two automotive coatings, a melamine-crosslinked acrylic resin and an acrylic polyurethane, as a function of artificial weathering ti me. Characteristics of the CL emission from coatings, the influence of light stabilizers and different types of sample were studied. The res ults indicate that the method is highly sensitive and can be used to m easure photodegradation in unstabilized and stabilized coatings after only 48 h and 100-200 h of exposure, respectively. Measurements can be carried out on free clearcoats or on clearcoats applied on metallic p anels. It is also possible to assess the degradation of individual lay ers in multiple-layer coating systems. Extrapolation to the failure ti me of coatings by CL is not yet achievable, but results show that the technique is useful for rapidly screening the relative performance of new coating formulations or light stabilizers added to clearcoats. (C) 1998 Elsevier Science Limited. All rights reserved.