MICROSCOPIC, SPECTROSCOPIC AND RHEOLOGICAL ANALYSIS OF SOLVENT-FREE ORGANIC COATINGS

The application of some new microscopic, spectroscopic and rheological methods to the study of solvent-free organic coatings is illustrated with a number of examples. A method For following the physical changes as a function of degree of conversion during cure of on epoxy film is described. By using a torsional dynamic mechanical analyser with cont rolled normal force, simultaneous data on modulus and shrinkage is obt ained, and events such as gelation and vitrification detected. Defects in cured allyl ether maleate-functional coatings are studied using co nfocal laser microscopy, atomic force microscopy and scanning acoustic microscopy. Confocal microscopy offers high surface contrast in combi nation with good in-depth resolution, but is limited to transparent ma terials. Atomic Force microscopy gives information regarding the exact topography of the surface of a speciment but is unable to characteris e the interior of the films. Acoustic microscopy has a too low in-dept h resolution to accurately locate the defects, but still provides info rmation about the surface of the sample. Finally, the degree of cure i n acrylate-functional hyperbranched coatings is investigated through m easurement of residual unsaturation with Roman spectroscopy. It is sho wn that applying a gold film to the substrate substantially improves t he signal-to noise ratio of the Roman spectrum.