Synthesis of model acrylic latexes for crosslinking with cycloaliphatic diepoxides

Two model acrylic latex systems were synthesized. One latex system was carboxyl functional, and prepared using methyl methacrylate (MMA) and butyl acrylate (BA) with methacrylic acid (MAA). The second latex system was hydroxyl functional, and prepared using MMA and BA with 2-hydroxyethyl methacrylate (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 calorimeter (DSC) were used to study the rheological and thermal properties of the crosslinked coatings. The film properties of the crosslinked latexes were 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 enhancement of the overall film properties. However, a balance of the crosslink density and the glass transition temperature was necessary for good adhesion. In addition, the carboxyl functional acrylic latexes displayed better overall properties than the hydroxyl functional acrylic latexes, and the polarity and steric hindrance of the ester crosslinks may play important functions in the observed properties. (C) 1999 Elsevier Science Ltd. All rights reserved.