Synthesis of model acrylic latexes for crosslinking with cycloaliphatic diepoxides

Two model acrylic latex systems were synthesized. One latex system was carb oxyl functional, and prepared using methyl methacrylate (MMA) and butyl acr ylate (BA) with methacrylic acid (MAA). The second latex system was hydroxy l functional, and prepared using MMA and BA with 2-hydroxyethyl methacrylat e (HEMA). Both the resultant latexes were crosslinked with a cycloaliphatic diepoxide (3,4-epoxycyclohexyl methyl-3',4'-epoxycyclohexane carboxylate). Dynamic mechanical thermal analysis (DMTA) and differential scanning calor imeter (DSC) were used to study the rheological and thermal properties of t he crosslinked coatings. The film properties of the crosslinked latexes wer e evaluated in terms of water absorption, gel content, Tukon hardness, pull -off adhesion, and hydrolytic stability. The increase in the latex carboxyl or hydroxyl functionality and glass transition temperature resulted in enh ancement of the overall film properties. However, a balance of the crosslin k density and the glass transition temperature was necessary for good adhes ion. In addition, the carboxyl functional acrylic latexes displayed better overall properties than the hydroxyl functional acrylic latexes, and the po larity and steric hindrance of the ester crosslinks may play important func tions in the observed properties. (C) 1999 Elsevier Science Ltd. All rights reserved.