Study Of High Solid-content Waterborne Polyurethane By Solvent-free Technique

Preparation of high solid-content waterborne polyurethane by conventional self-emulsifying method with solvent-free technique is discussed firstly in this thesis,also some factors in preparation process of waterborne polyurethane which affect the waterborne polyurethane solid content,emulsion viscosity and film properties were investigated systematically.It was found that the stable polyurethane emulsion with solid content over 50%and appropriate viscosity could be easily prepared by controlling[NCO]/[OH]value within 1.4-1.7,DMBA content within 3.3-4.6%,and also by using polyester polyol?PBA?as the soft segment.The typical polyurethane chain structure was confirmed by Fourier transform infrared spectroscopy and ¹³C-NMR,and the film showed good crystalline properties and mechanical properties.There were still problems in the preparation,for example,the viscosity of the prepolymer was so high that it was difficult to control the dispersion process.In order to overcome the shortcomings of conventional methods in the synthesis of waterborne polyurethane,a novel method of preparation of waterborne polyurethane by self-emulsifying miniemulsion polymerization was proposed secondly in this thesis.A correlation between ¹H-NMR spectra and the ratio of urethane groups to urea groups of waterborne polyurethane was put forward to investigate the competition of polymerization during self-emulsifying miniemulsion polymerization.The concentration ratio of urethane groups to urea groups?F?can be used to indicate the competition of the isocyanate and alcohol polymerization and of the isocyanate and water.The effect of some factors on reaction rate and F value during preparation process of waterborne polyurethane was discussed systematically in this thesis.It showed that the using of composite polyols?PBA/PTMG?,controlling of DMBA content within 3.6-5.5%,keeping the polymerization temperature with 50°C,and also adding the zirconium chelate as catalyst and the liquid paraffin as co-stabilizers can effectively improve the response rate of isocyanate and alcohol polymerization,and inhibit the polymerization of isocyanateandwater.Finally,It can conclude that the solvent-free waterborne polyurethane with high solid-content?MWPU?can be prepared by the method of self-emulsifying miniemulsion polymerization.The results show that:the terminal-NCO prepolymer can be prepared by controlling composite polyols m?PBA2000?and m?PTMG2000?with the ratio of 2:1,also PTMG650 was used as polyol in miniemulsion polymerization,and the solid content was increased,the proportion of reaction of isocyanate groups to alcoholic hydroxyl was increased too.The tensile strength of the film was 24MPa,extensibility was 1116%,and the film was with better heat resistance?T_d=308.51??and the solid content reached 54%.