Abstract: An acetoacetylated polyacrylate and a vinylic groups ended polyurethane were synthesized. In the presence of a basic catalyst, they can crosslink with each other via the Michael reaction to prepare a thermoset coating at ambient temperature. A model of this crosslinking system, the reaction of ethyl acetoacetate(EAA)with methyl acrylate(MA), was designed to investigate the crosslinking mechanism. The results indicate that the two active hydrogen atoms of the acetoacetyl functionality can participate in the reaction and both mono- and bis- adducts are formed. The yield of bis-adduct increased with decreasing feeding molar ratio of EAA and MA. Two composite coatings with molar ratios of acetoacetyl content of polyacrylate to double bond content of polyurethane being 0.6/1 and 1/1 were prepared. The former coating showed higher crosslinking degree and better properties than the latter one.

Key words: acetoacetylate, polyacrylate, polyurethane, vinylic group, crosslinking mechanism