Scratch and mar and other mechanical properties as a function of chemical structure for automotive refinish coatings

Due to continued customer demand for better quality and more durable coatings, interest in improving the physical damage resistance of automotive refinish coatings has intensified. New coating materials are being explored based on oligomer chemistry that show promise in providing improvements in both physical and chemical properties, and in the long-term maintenance of those properties. In this paper, measurement techniques for monitoring chemical and mechanical property changes, including cure rate, crosslinking, photo-oxidation index, hardness and scratch and mar performance, were explored. The use of the single scratch indentor, a method pioneered in this laboratory, provides a basis for mechanical property evaluation. Constant temperature and relative humidity (CTR) storage and QUV accelerated weathering were used in this study. Mechanical performance was determined using hardness measurements, nano-scratch experiments and wet/dry rubtests. Infrared was the primary method of chemical analysis. This characterization was done to broaden our understanding of structure/property relationships, as well as to provide a more reliable prediction of service life.