A new resin for photocurable electrical insulating varnishes

A new polyester resin for photocurable electrical insulating coatings was synthesized. The resin was diluted in hexanediol diacrylate (HDDA) monomer. 2-Hydroxy-2-methyl-1-phenyl-propane-1-one was aggregated to the coating formulation as a photoinitiator of the UV radiation curing. Coating film samples, 50 μm thick, were prepared on cooper plates using an appropriated extensor. Coating films were cured under different UV doses at room temperature using an UV tunnel. The UV doses of 400 mJ cm−2 has promoted the higher curing degree without detectable coating degradation. Some samples were submitted to dual-cure (or hybrid cure) that means UV curing followed by thermal curing for 2 h at 240 °C in order to promote the improvement of some ultimate properties. Both samples, UV-cured and UV/thermal dual-cured, were evaluated.