The structure and properties of acrylic-polyurethane hybrid emulsions and comparison with physical blends

Aqueous acrylic-polyurethane hybrid emulsions were prepared by semibatch em ulsion polymerization of a mixture of acrylic monomers (butyl acrylate, met hyl methacrylate, and acrylic acid) in the presence of polyurethane dispers ion. Equivalent physical blends were prepared by mixing acrylic emulsion an d polyurethane dispersion. The weight ratio between acrylic and polyurethan e components varied to obtain different emulsion properties, microphase str ucture, and mechanical film properties of hybrid emulsions and physical ble nds. Particle size and molecular mass measurements, scanning electron micro scopy, glass transition temperature, and rheological measurements performed characterization of the latex system. The mechanical properties were inves tigated by measuring tensile strength and Koenig hardness of dried films. T he experimental results indicate better acrylic-polyurethane compatibility in hybrid emulsions than in physical blends, resulting in improved chemical and mechanical properties. (C) 2000 John Wiley & Sons, Inc.