The Research Of The MDI-50 Waterborne Polyurethane Emulsion's Preparation And Modification

To enhance the performance of waterborne polyurethane products by physical or chemical means has been paid more attention in polymer material field.In this paper the dispersity of nano-TiO₂ in waterborne polyurethane?WPU?was improved and nano-TiO₂ which surfaces were modified was used as ultraviolet absorber.Nano-TiO₂ was modified using stearic acid and r-aminopropyltriethoxysilane?KH550?as modifier in order to improve the dispersion of nano-TiO₂ in WPU.Through the analysis of activation index,FTIR,TG and SEM,the optimal modifying conditions were as follows:modifier dosage was 7%,modification temperature was 60?,modification time was 2 h.The effect of KH550 modified nano-TiO₂ was better than that of stearic acid.WPU was prepared with MDI-50 and polypropylene glycol?PPG?as the main raw materials,and the effects of R?NCO/OH?,dimethylolpropionic acid?DMPA?content,prepolymerization temperature,prepolymerization time,chain reaction temperature,chain reaction time and emulsifying temperature on the properties and appearance of WPU emulsion were discussed.The optimum preparation project was when R value was 3,DMPA content was7%,prepolymerization temperature was 55 ?,prepolymerization time was 2 h,chain reaction temperature was 70 ?,chain reaction time was 2.5 h,and emulsifying temperature was room temperature.Then WPU/ nano-TiO₂ nanocomposites were prepared by mechanical blending and characterized by FTIR,TG and UV-vis.The results showed that the thermal stability and ultraviolet absorption intensity of the WPU can be improved by the addition of nano-TiO₂,and would increase with the increase of the modified nano-TiO₂ mass.