Painted Thermoplastic Olefin System: Assessing the Variability of Adhesion Promoter Adhesion Performance following UV Exposure

Abstract

The development of test methods for assessing fundamental properties of materials which influence in-service coating adhesion is important for screening potential material candidates. The main focus of this study was to develop a methodology for screening adhesion-promoting primer materials used on thermoplastic olefin (TPO) systems as to their susceptibility to UV degradation. This work assesses the adhesion performance of a single unfortified (no UVA or HALS additives) 2K polyester−urethane topcoat over a number of commercially available adhesion promoter systems following ambient UV exposure. Adhesion performance is correlated with the relative photodegradation of the adhesion promoter materials. This study was specifically designed to simulate conditions of thin topcoat application and/or loss of light stabilizers in the paint by adventitious processes that would render the adhesion promoter/topcoat interface exposed to ambient UV radiation. Results of the adhesion testing showed that there is a wide range in the performance of the adhesion promoters used in this study. Adhesion loss following ambient exposure to UV radiation was observed in as little as 100 h to greater than 6300 h of exposure. The variation in the performance of the adhesion promoters was found to correlate with the degree of photooxidation of the materials. These results suggest that this type of a methodology would be useful in assessing the relative sensitivity of polymers used in adhesion promoter formulations when exposed to ambient weathering conditions.