Effect of Hydroxyethyl Acrylate on the Properties of Polyurethane-Acrylics Hybrid Latexes

Polyurethane-acrylics (PU-AC) hybrid latexes were prepared using isophorone diisocyanate, dimethylol propanoic acid and polypropylene oxides of different molecular weights as main materials for PU component, and butyl acrylate, methyl methacrylate and a crosslinker, trihydroxymethyl propanetriacrylate (TMPTA) as main acrylic monomers. Hydroxyethyl acrylate (HEA) was used as the coupling agent between PU and AC. In a first step, a method for evaluation of PU grafting to AC polymers was proposed and verified through designed experiments. The influences of reaction temperature of HEA and NCO in PU prepolymer and of amount of added HEA on properties of the final latex and of the polymer, for instance, PU grafting, particle size and distribution in final PU-AC latex, polymer crosslinking and water adsorption of latex films, were explored. With increase in the reaction temperature between HEA and NCO, the final residual NCO gradually decreased. With increase in HEA amount relative to NCO, expressed as HEA/NCO in mole, the particle size and PU amount grafted to AC polymers both increased when the HEA/NCO was below 1.0; while both the particle size and PU amount grafted remained relatively constant when this ratio was above 1.0. Water adsorption of the latex films was in significant decrease with increasing HEA as the coupling agent.