Study On Modification Of Waterborne Polyurethane

Polyurethane is a kind of polymer which contains -NHCOO- groups on the main chain that known as polyurethane. Waterborne polyurethane contains little organic solvents which caused low cost, no burning and no pollution. However, the water resistance and solvent resistance of the waterborne polyurethane is bad; and the solid content of the waterborne polyurethane is low.In order to improve the water resistance and solvent resistance of the waterborne PU, the epoxy resin was used to modify the waterborne polyurethane; And in order to improve the solid content of the waterborne PU emulsion, the hyperbranched PU molecular was synthesised to reduce the chain winding.In this paper, the waterborne polyurethane emulsion modified by epoxy resin was prepared using toluene diisocyanate (TDI), polyether (GE-210),1,4-butanediol (BDO). dimethylolpropionic acid (DMPA), epoxy resin and hydroxypropyl acrylate (HPA). Effects of the molar ratio of the -NCO and the -OH group in the prepolymer (R), the content of Small molecule chain extenders, hydrophilic chain extender and epoxy resin on the size, viscosity, stability of the emulsion and water-resistance of the film was studied. The particle size of the WPU was small, the viscosity was low, as well as good stability of the emulsion and good water resistance of the coating.The hyperbranched polyester H10 was prepared using PEL as a core molecule and DMPA as monomer, and a series of UV-curable Waterborne Hyperbranched Polyurethane was synthesized by modifying the hyperbranched polyester H10 with succinic anhydride, TDI and HPA. The properties of the emulsion with different content of succinic anhydride and TDI-HPA was investigated by measuring the viscosity and the particle size. The hyperbranched polyurethane emulsion has low viscosity, small particle size and narrow size distribution, as well as good stability.