Synthesis And Application Of Flame Retardant Waterborne Polyurethane Modified By Nano Silica

Waterborne polyurethane has been widely used for little organic solvent and a series of advantages such as non-toxic,eco-friendly,easy to use,wear resistance,high elasticity and high strength.The weakness of flammability of its coat has limited its applications in many fields.There are some problems on the fire retardant technology of waterborne polyurethane: 1)bad flame retarded effect;2)high cost;3)the flame retardant has negative effect on physical properties of waterborne polyurethane.Therefore,the study of flame-retarding waterborne polyurethane with good physical properties has important significance in practice.In this paper,firstly,nano-SiO₂ sol was prepared by different methods.Then,a method was choosed according to the compatibility of nano-SiO₂ sol with waterborne polyurethane.On the basic of it,process parameters were discussed and studied.Nano-SiO₂ sol was used to modify waterborne polyurethane,and the properties was then explored.The details are as follows.?1?Nano-SiO₂ sol was prepared from TEOS as raw material,absolute alcohol as solvent and sodium dodecyl benzene sulfonate?SDBS?as surfactant.The systerm of this nano-SiO₂ sol mixed with waterborne polyurethane was more stable than others.?2?When the volume ratio of water and TEOS was 2:4,reaction time was 4 hours,it had a high percent conversion?6.21%?,closed to the theory percent conversion?6.5%?.?3?When the amount of nano-SiO₂ sol in waterborne polyurethane?WPU?was 20%?w/w?,the WPU composites exhibited better properties.It was shown that dry time was 2 h,hardness was H,tensile strength was 45.93 MPa,elongation at break was 289.73%,water absorption was 2.17%,oxygen index was 26.5 and the thermal decomposition temperature of film coating was increased nearly 40?.Nano-SiO₂ sol in WPU was called Si-WPU.Finally,the novel flame retardant containing phosphorus-nitrogen?CPM?was synthesized.Flame retardant waterborne polyurethane modified by nano SiO₂ was prepared,while CPM was mixed with Si-WPU.CPM effected on the physical and chemical properties and flame retardant properties of Si-WPU was emphatically studied,and the flame retarding mechanism of themodified flame retartant waterborne polyurethane was analyzed.The details are as follows.?1?flame retardant containing phosphorus-nitrogen?CPM?was prepared from 25 mL of phosphate ester and 3.5g of melamine under the conditions of the reaction temperature at 120?and the reaction time for 3 h.?2?When the mass percent of CPM in Si-WPU was 20%,the Si-WPU modified by CPM exhibited better properties.The testing results was indicated that dry time was 3 h,hardness was HB,tensile strength was 43.37 MPa,elongation at break was 264.32%,water absorption was2.73%,oxygen index was 29.5.?3?flame retardant containing phosphorus-nitrogen?CPM?had synergistic effect with the nano-SiO₂,which contributed to the combustion of carbon.Element analysis test indicated the combustion of carbon was improved to 57.71%.