A kinetic study in emulsion polymerization of polyurethane‐acrylate hybrids

Polyurethane (PU) anionomer having 2‐ethoxymethacrylate terminal groups was prepared in a methyl methacrylate/n‐butyl acrylate mixture as a reactive diluent, following a prepolymer mixing process. This prepolymer‐acrylic monomer mixture was chain extended in a water/surfactant solution using different dispersion speeds. Stability tests of PU‐acrylic monomer dispersions before polymerization were performed at different temperatures by following the particle size evolution. After the dispersion process the kinetics of batch emulsion polymerization at 70°C using different concentrations of initiator was investigated. Data are compared with published results of batch emulsion copolymerization of methyl methacrylate/n‐butyl acrylate. The effect of triethylamine, used in the prepolymer synthesis, on the emulsion polymerization of acrylic monomers was also studied. The kinetic results indicate that during emulsion polymerization of PU acrylic mixture, some coagulation takes place, mainly due to changes in ionic strength of the medium, before stable latex particles are formed. The presence of the PU prepolymer seems not to affect the kinetics of batch copolymerization of methyl methacrylate/n‐butyl acrylate monomers.