Preparation of zinc methacrylate-methylmethacrylate-butyl acrylate emulsions and their application in exterior paints

Abstract

Semi-batch emulsion polymerization of methyl methacrylate-butyl acrylate- methacrylic acid monomers were carried out with the addition of nano ZnO to the monomer feed, to obtain a binder for exterior architectural paints. Nano ZnO reacted spontaneously with acid groups to form zinc methacrylate or dimethacrylate which participated in crosslinking reactions. The amount of nano ZnO added was increased up to the equivalence point and in several cases exceeded for unmodified, hydrophilic or hydrophobic silane modified nano zinc oxides. The emulsions and clear polymer films obtained from them were characterized with conventional methods. FTIR and UV/Vis spectra confirmed the transformation of nano zinc oxide up to the equivalence point.The emulsions were used for preparing of opaque and transparent colored paints which were tested with UV exposure-condensation accelerated weathering along with clear polymer films. The color parameter, gloss and water contact angle changes were determined for every 250 h up to 1000 h. Optical microscopy and for some cases AFM, FTIR and FESEM were also used for further characterizations. Presence of zinc methacrylate crosslinking and in some cases, additional presence of nano ZnO, provided blistering prevention and improvement of gloss and color stability.