Bayer Material Science LLC develops & tests UVA-curable coatings for aircraft topcoats

Ultraviolet A (UVA)-curable coatings are being researched as an alternative to traditional two-component (2K) polyurethane aerospace topcoats because of their rapid cure rates, low volatile organic compounds (VOCs), low volatile hazardous air pollutants (VHAPs) and high performance properties.

Bayer MaterialScience LLC and Deft Inc., a supplier of coating systems for the aerospace and industrial markets, developed UVA-curable coating formulations that were evaluated against aerospace standards for topcoats. Based on these findings, Todd Williams, industrial post-doctoral researcher, Bayer MaterialScience LLC, presented “Development of UVA-Curable Coatings for Aircraft Topcoats” at the recent RadTech’s UV/EB 2010 Technology Expo and Conference in Baltimore.

Conventional coatings in the aerospace market historically have been based upon 2K polyurethane coatings that require 72 hours to fully develop their physical properties. The development of UVA-curable aerospace coatings is targeted to significantly decrease refurbishing time through greatly reduced curing time.

According to Williams, UVA-curable coating formulations display promising physical properties. A UVA-curable formulation was applied to C-130 and F-16 aircraft as a stencil coating and was periodically evaluated for color change and gloss retention. After 600 flying hours, the stencil coatings on the C-130 had ?E values comparable to the conventional polyurethane fluoropolymer coatings.

Aerospace coatings require a compromise of both chemical resistance and flexibility while maintaining hardness. In this study, formulations that yielded such a balance of chemical resistance, flexibility, and hardness were obtained using a combination of hard and soft urethane oligomers and reactive diluents.

Williams explained, “Gloss reduction of these coatings was achieved through a combination of flatteners and oxygen inhibition, leading to flexible, low gloss formulations.” He continued, “Weathering of UVA aerospace systems is another critical property that can be chiefly controlled by raw material selection.” Through this evaluation, the overall performance of UVA-curable coatings has been shown to rival that of conventional polyurethane coatings.

www.bayermaterialsciencenafta.com.