Syntheses And Properties Of Waterborne Polyurethane/Polyacrylate Core-Shell Emulsions

In this work, NCO-terminated prepolyurethane was firstly prepared with toluene diisocyanate (TDI), polypropylene glycol (N220) and dimethylolpropionic acid (DMPA), and then the aqueous polyurethane emulsion was obtained by adding water under vigor agitation into the neutralized prepolymer by triethylamine (TEA). Aqueous acrylic-polyurethane hybrid emulsions were prepared by the core-shell emulsion copolymerization of acrylate and polyurethane dispersions. PUA emulsion particles were characterizaed by SEM and TEM, and core-shell structure of PUA particles was confirmed by TEM and SEM images.The effects of reaction time, temperature, the ratio of soft and hard segment, the type and dosage of emulsifier and initiator as well as the content of DMPA on the particle size and its distribution, morphologies of particles; colloid stability, properties of eumlison and its film were investigated.For the preparation of aquoues PU dispersion, the prepolymer should be manufacuterd around 80℃for 65 mins, and DMPA content should be 6% of the total PU monomer, the molar ratio of diisocyanate to polyether (N220) should be 2.5~2.9, and the ratio of diisocyanate to total hyxroxyl monomers should be 1.6 to 1.8. In the final PU dispersion, carboxylic content is about 2.5% and the ratio of soft segments to hard segments is 1 : (1.0~1.25) and ethylenediamine (EDA) can be used as extender and its dosage can be controlled by the ratio of amino group to residential isocyanate groups is about 0.30 to 0.50.