Investigation Of The Synthesis And Modification Of Water-Borne Polyurethane Resins

Recently, in order to improve the integrative performances of water-bornepolyurethane (WPU) and enlarge its application fields, modification of WPU has beenbecame one of the key point in the field. In this dissertation, it consists of three mainparts about modification as follows: main chain modification, epoxy resin complexmodification and montmorillonite (MMT) nanocomposite modification.Main chain modification. The effect of the ratio of-NCO/-OH and the amount ofDMPA in the reaction system on the performance of WPU were discussed, then theeffect of castor oil as cross-linked agent and amines extender such as ethylene diamine,hexamethylene diamine, diethylenetriamine etc., on the properties, the particle size,and viscosity of the WPU dispersion was studied. The results showed that themechanical properties was determined by the ratio of -NCO/-OH, and the appearanceof dispersion, viscosity, the particle size and water-resistance of WPU film weredetermined by the content of DMPA. Castor oil, instead of conventionalmicro-molecule cross-linked agent, not only reduced the cost of WPU product but alsogot the better impact. The best mechanical properties was obtained when the weightcontent of castor oil was 7.1%. The mechanical properties, chemical-resistance andthermal property of WPU film would be better when the content of diethylenetriaminewas 13%.Graft modification by epoxy resin. While different kinds of amines used asexternal extenders, both the appearance, stability of WPU dispersion and themechanical properties, chemical-resistance, the thermal property of WPU filmmodified by epoxy resin were studied in details. It showed that with the increase ofepoxy group, the stability and the appearance of WPU dispersion became worse, but the mechanical properties, chemical-resistance and thermal property of WPU filmwould be better, especially with the weight content 13.7% of epoxy resin. The stabilityof WPU dispersion became worst because of the co-existence of epoxy and amine.Complex modification by inorganic particles. Here MMT was organicallymodified by the self-made hydroxyl terminated cationic WPU polyelectrolyte and theorganic MMT (OMMT) was obtained. Then the WPU/clay nanocomposites wassynthesized with the OMMT. The OMMT was characterized by WXRD, FT-IR, AASetc. while the PU/OMMT nanocomposites was investigated by TEM, DSC and TGA.It was found that the d spacing of the silicate layers increased from about 1.26 nm to2.02 nm, compared with the Na-MMT, which indicated the better intercalation ofcationic polyurethane chains between the layers of MMT. OMMT was intercalated andexfoliated by the polyurethane and well dispersed in nano-size in the polymer. The Tgof WPU/OMMT nanocomposites increased with increasing the OMMT, and thethermal stability was improved.