Synthesis and crosslinking mechanism of a polyacrylate/polyurethane composite coating

A polyacrylate comprising acetoacetyl group and a polyurethane with vinyl end groups have been prepared. These two polymers could crosslink with each other to form a composite coating in the presence of a basic catalyst at room temperature. A model Michael reaction between ethyl acetoacetate (EAA) and methyl acrylate (MA) was used to investigate the crosslinking mechanism. The results indicate that the two active hydrogen atoms in the acetoacetyl group could both react with vinyl groups to form mono- and bis-adducts in a two step process.