Desempenho de tintas de acabamento frente às radia？？es ultravioleta, UVA e UVB, e condensa？？o de umidade

it is well known that the ultraviolet radiation directly affects physical and chemical properties of a large number of materials, specially organic paint coatings, by means of the reduction of its lifetime. in this work, the authors have studied the performance of some topcoat paints (aliphatic polyurethane, acrylic aliphatic polyurethane, acrylic polisiloxane, epoxy, and alkyd) in relation to the effects of the ultraviolet radiation. some theoretical concepts concerning the influence of ultraviolet radiation on the organic coatings degradation processes are presented, the experimental work is described and the results obtained are shown. the study involved the exposition of the paints to the uva and uvb radiation, and the evaluation was carried out by the variations of gloss, color and chalking formation. the results obtained from the two sources of radiation were qualitatively similar. as it was expected, the analysis of the overall results shows that the uvb radiation caused greater loss of gloss in a smaller time of exposition, because of its higher level of energy in comparison to the uva radiation.