NIR LEDs and NIR lasers as feasible alternatives to oven processes
Near-infrared (NIR) laser sources (800–1000 nm) can potentially reduce the processing time for curing by a fast heating and incorporation of NIR absorbers into the coating.
The latter converts NIR laser light absorbed into thermal energy. This curing technique was successfully applied to one-component thermoset coatings based on blocked polyisocyanate/hydroxy-polyester and melamine formaldehyde/hydroxy-acrylate resins with heptamethine cyanines as near-infrared absorbing material. The laser curing was additionally compared with LED sources. In general, the curing time significantly decreases in comparison with traditional heat sources. Furthermore, the photopolymerisation of acrylates or epoxides can be induced simultaneously by adding suitable initiators due to photochemical generation of radicals and cations.
Substitution of oven techniques
Curing of the thermoset resin system and the photopolymerisation process created interpenetrating networks. Principally, the techniques reported based on photonic NIR sources may help to substitute oven techniques where thermal activation of curing reactions is typically induced by oven or heating with infrared radiators for coating applications.
The study is published in: Journal of Coatings Technology and Research, November 2019, Volume 16, Issue 6, pp 1527–1541.
