The Roles of Artificial Versus Natural Exposure In Predicting Exterior Durability: Desperately Seeking Correlations

摘要

Architectural coatings used in exterior applications are subject to a multitude of exposure conditions depending in part on when exposed at a particular geographical location, orientation and exposure direction. The observed modes of failure are equally diverse, dependent upon exposure condition, as well as chemistries, formulation and mechanism. The desire to create reproducible exposure conditions and accelerate the testing process has lead to the development of a number of artificial exposure instruments and processes. The ultimate success in the utilization of these technologies depends upon finding the correlations between artificial and natural exposure, failure mode and mechanism. The study described herein examines the correlations between artificial and natural exposure for nearly 10,000 measurements on over 200 unique paints. Reasonable correlations are found when the substrates are dimensionally stable and failure modes are relatively simple and similar. However, for many real world, less dimensionally stable substrates and complex failure modes correlations are not found.