Soft Segment Structure Design And Performance Of High Solid Waterborne Polyurethane Emulsion

In recent years,as environmental protection awareness has taken root in the hearts of the people,the market demand for waterborne polyurethane emulsions(WPU)has rapidly expanded,and research on waterborne polyurethanes at home and abroad has gradually deepened.Waterborne polyurethanes are widely used in many fields such as coatings,adhesives,leather finishing and so on.But they also have shortcomings.As a dispersion medium,the latent heat of water evaporation is large,and the preparation of high solid content waterborne polyurethane emulsions has become an important research direction.In this paper,the influence of the composition and structure of polyol on the solid content and performance of WPU are mainly explored.The mainly aspects of research are as follow:(1)WPU was synthesized by a single type of polyol as the soft segment,and the latex film was prepared.The structure of film was characterized by IR and XRD in detail.The solid content of WPU was measured and the particle size was analyzed by a particle size analyzer.The thermal behavior of film was analyzed by DSC and the mechanical properties of film were investigated by the universal testing machine.The results show that the high solid content waterborne polyurethane with polyester is easier to be synthesized.The performance of WPU is improved with the degree of crystallinity.For WPU by using phthalic anhydride polyester FA-2817P(F0)as the soft segment,the average particle size is220 nm,the solid content is 54%,the storage stability is more than six months,the tensile strength of film is 12.5 MPa,and the elongation at break is 1622%.For WPU by using neopentyl adipate diol N-56(F1)as the soft segment,the average particle size is 295 nm,the solid content is 61%,the storage stability is more than six months,the tensile strength of film is 25.6 MPa,and the elongation at break is 1871%.(2)WPU was synthesized by three polyester polyol of F0,F1,polycaprolactone diol(PCL)as the mixture soft segment the latex film was prepared.The structure of film was characterized by IR and XRD in detail.The solid content of WPU was measured and the particle size was analyzed by a particle size analyzer.The thermal behavior of film was analyzed by DSC and the mechanical properties of film were investigated by the universal testing machine.The results show that the mechanical properties of polyurethane can be improved by the mixture of crystalline polyester and non-crystalline polyester.However,as the increase of crystalline polyester,the solid content and stability of the emulsion are reduced.For WPU by using the mixture of F1 and PCL,with the increase of PCL,the solid content decreases from 62.7% to 41.2%,the storage stability is gradually reduced for less than six months,the tensile strength increases from 16.7 MPa to 40.6 MPa,and the elongation at break rises from 1840% to 1992%.(3)WPU was synthesized by polyester polyol of F0,F1 and polyether polyol of PTMG as the mixture soft segment of polyester and polyether and the latex film was prepared.The structure of film was characterized by IR and XRD in detail.The solid content of WPU was measured and the particle size was analyzed by a particle size analyzer.The thermal behavior of film was analyzed by DSC and the mechanical properties of film were investigated by the universal testing machine.The results show that the solid content and storage stability of WPU can be improved by the mixture of polyether polyol and polyester polyol.When the structure regularity of the soft segment is lower,the comprehensive properties of the emulsion are better.The average solid content of the synthesized emulsion is above 55%,and the storage stability is more than six months.The tensile strength of the film is slightly increased(17.3 MPa),and the elongation at break is increased to 2536%.(4)WPU was synthesized by using F0 and F1 as the soft segment and modified with alcohol hydroxy silicone oil Silok8807(Si8807).When the dosage of Si8807 is 2wt% and4wt%,the emulsion performance is relatively excellent.When the amount of Si8807 is2wt%,the solid content of the emulsion can reach to 53.5%,the viscosity of the emulsion is 258.6 m Pa·s,the storage stability is 6 months,the tensile strength is 47.4 MPa,and the elongation at break is 1901%.When the amount of Si8807 is 4wt%,the solid content of the emulsion can reach to 51.7%,the viscosity of the emulsion is 4283 m Pa·s,the storage stability is 6 months,the tensile strength is 53.8 MPa,and the elongation at break is 1951%.All the results show that the reasonable design of the soft segment of WPU can improve the performance of WPU and increase the solid content of emulsion,which provides a new method for the development of WPU with high solid content.