Reflectance and Related Studies of The Weathering of Surface Coatings

Abstract

This project is concerned with the way in which a selected combination of analytical techniques can be applied to the study of the various ageing processes which occur in surface coatings during exposure. Particular emphasis in this respect is placed on the development and application of the goniophotometric technique to the quantitative characterisation of reflectance changes brought about by weathering - a usage which appears not to have been previously exploited to any notable extent. In conjunction with goniophotometry, a variety of other techniques are also used, notably scanning electron microscopy, multiple internal reflection spectroscopy and surface roughness measurement, with their respective data being correlated as far as possible. The actual coatings materials examined in this way comprise, in the first part, a range of commercial paints chosen to represent a cross-section of those currently available. Their ageing study is then followed by a more detailed investigation into the weathering mechanism of a particular class of coatings - namely, those based on poly (vinyl chloride) (PVC) - including the roles played by the various additives present in the system. Finally, in addition to both the natural and artificial weathering tests which have been conducted at various outdoor sites and under various conditions, an adjunctive case study of the interaction of pvc with nitric oxide is also described.