Preparation and properties of aqueous polyurethane dispersions

Waterborne polyurethane as a new polymer dispersion was synthesized by using relatively hydrophilic polyols. This polymer was prepared from polycaprolactone diol (Capa 225), toluene diisocyanate (TDI), 1,4-butane diol (BDO) as chain extender, and dibutyltin dilaurate catalyst. Grafted polyurethane was prepared with chlorinated poly(ethylene glycol monomethyl ether) (PEGMME) in the presence of sodium hydride (NaH). Chlorinated PEGMME was also prepared by reaction of PEGMME with thionyl chloride in dried toluene. FTIR and H-1 NMR of the waterborne polyurethanes were used to characterize the grafted PU. The effects of various molecular weights of PEGMME as non-ionic hydrophilic segments were studied. The particle size and viscosity of dispersions were systematically analyzed. It is found that by increasing the molecular weight of the grafted PEGMME, the particle size of dispersed polyurethane is decreased, and viscosity is increased.