Method to determine chemical composition distribution on matte coating surfaces using Raman microscopy

A method to obtain quantitative information about the chemical composition spatial distribution on rough (R-a between half a micrometer and tens of mi crometers) surfaces is developed by using a Raman microscopy technique. It is tested on a wrinkled polyesterurethane-acrylate powder coating surfaces with pronounced star-patterned (mountains and valleys) structures. Raman sp ectra at different features on the surface are analyzed quantitatively by u sing a least-squares fitting method based on coating components' spectra, t aking into account chemical reactions which occurred during cure. This meth od is able to extract the same information as qualitative analysis could fr om component Raman peaks when large composition heterogeneity occurs. In ad dition, it provides more subtle information when chemical composition distr ibution is less marked. This feature is particularly useful for establishin g the cause of sophisticated surface structures. The origin of the surface structures is attributed to spinodal decomposition frozen by chemical react ions during cure.