Application of dual-function microgels in ultraviolet/thermal dual-cure clear coats

Abstract

Hydroxyl-functional nanosized microgels were synthesized by nonaqueous dispersion polymerization with caprolactone-modified hydroxyethyl acrylate as a stabilizer and 1,6-hexanediol diacrylate as a crosslinker. The dual-function microgels were prepared by the reaction of the hydroxyl groups of the microgel with isocyanatoethyl methacrylate for use in a UV/thermal dual-cure process. The synthesized microgels were identified by Fourier transform infrared spectroscopy, transmission electron microscopy, and dynamic light scattering. The effects of the addition of the microgels on the rheological properties, curing behavior, and film properties were also investigated. The addition of the microgels resulted in a lower viscosity and shear thinning behavior in the coating solution. The glass-transition temperature of the cured films decreased with the addition of the microgels because of the flexible functional stabilizer chain that could participate in UV and thermal crosslinking. The scratch resistance of the cured coating also increased because of the increased ductility of the film caused by the soft microgel. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2012