Crosslinking of acrylic latex coatings with cycloaliphatic diepoxide

Acrylic thermosetting latexes were synthesized using methyl methacrylate (MMA) and butyl acrylate (BA) with methacrylic acid (MAA) or 2-hydroxyethyl methacrylate (HEMA). The MAA or HEMA was incorporated to provide the latexes with carboxyl or hydroxyl functionality, respectively. A cycloaliphatic diepoxide (3,4-epoxycyclohexyl methyl-3′,4′-epoxycyclohexane carboxylate) was used to crosslink with hydroxyl or carboxyl functional latexes. The coatings were crosslinked as a function of temperature, time, and the amount of the crosslinker. The crosslinking reactions were monitored using differential scanning calorimeter, IR spectroscopy, and dynamic mechanical thermal analysis. The coatings properties were evaluated in terms of water absorption, gel content, pencil hardness, and pull-off adhesion. The morphology of the latex coatings was studied using atomic force microscopy. The spectroscopic and rheological data showed that the cycloaliphatic diepoxide effectively crosslinked both the hydroxyl and carboxyl functional latexes. Carboxyl latex coatings were more reactive than hydroxyl latex coatings. The water resistance, solvent resistance, pencil hardness, and pull-off adhesion improved with the crosslinking temperature, time, and the amount of the crosslinker.