A study of the effects of postcure treatments on polyester-melamine coating matrices

The effect of postcure high energy (ƴ), ultraviolet (UV) and thermal treatment on the properties of polyester–melamine clearcoats of a range of compositions has been investigated. Two initial cure conditions were used, of which one was “optimally” cured and the other undercured. It was found that postcure treatments, particularly ƴ and UV, led to coatings of similar mechanical and thermal properties irrespective of initial cure, although the change in properties on postcure treatment was greater for the under-cured samples. The results were interpreted in terms of the effect of the treatments on the structure of the crosslinked matrices. The study suggests the possibility of the development of a dual-cure process for polyester–melamines, whereby cure optimization and property improvement can be achieved. This could also be used to “correct” for small variations in thermal cure levels brought about by adventitious online fluctuations in cure oven conditions.