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 controlled normal force, simultaneous data on modulus and shrinkage is obtained, and events such as gelation and vitrification detected. Defects in cured allyl ether maleate-functional coatings are studied using confocal laser microscopy, atomic force microscopy and scanning acoustic microscopy. Confocal microscopy offers high surface contrast in combination with good in-depth resolution, but is limited to transparent materials. Atomic Force microscopy gives information regarding the exact topography of the surface of a speciment but is unable to characterise the interior of the films. Acoustic microscopy has a too low in-depth resolution to accurately locate the defects, but still provides information about the surface of the sample. Finally, the degree of cure in acrylate-functional hyperbranched coatings is investigated through measurement of residual unsaturation with Roman spectroscopy. It is shown that applying a gold film to the substrate substantially improves the signal-to noise ratio of the Roman spectrum.