Preparation And Research Of Flame Retardant Waterborne Polyurethane Coating

Waterborne polyurethane coating（WPU）is a kind of environmentally friendly waterborne coating with non-toxic,non-polluting environment and high hardness.Compared with traditional solvent-based polyurethane coating,WPU is regarded as an effective substitute for solvent-based polyurethane coating because of its environmental protection production process,no large amount of organic solvents,low VOC release and other characteristics.At present,it is widely used in automobile coating,metal anticorrosion,furniture coating and other fields,with high research value and market prospect.However,the lack of flame retardancy of waterborne polyurethane coating limits its development and application in the field of flame retardancy functionalization.Therefore,it is urgent to solve the problem of flame retardancy modification of waterborne polyurethane coating without affecting the original performance of coating.In this paper,ethylenediamine（EDA）was used as a chain extender to react with isocyanate which was not fully reacted in the prepolymer.The urea bond with greater polarity than the carbamate group in the prepolymer was formed and the waterborne polyurethane coating with better properties was prepared.On this basis,the flame retardant containing phosphodiol[bis（2-hydroxyethyl）amino methyl]-diethyl phosphate（FRC-6）replaced the original chain extender 1,4-butanediol（BDO）as the prepolymer.The phosphorus-containing waterborne polyurethane flame retardant coating（FPU）was prepared by chemical reaction method by introducing flame retardant elements and flame retardant groups into WPU molecular chain.Finally,nano-silica（A-Si O₂）was added to FPU after surface modification with the coupling agent vinyl triethoxysilane（A-151）as A co-effective flame retardant.Phosphorus/silicon coefficent flame retardant waterborne polyurethane coating（SFPU）was obtained.The effect of the amount of flame retardant on the final WPU flame retardant modification was studied.The main research contents are as follows:（1）Preparation and Research of Waterborne Polyurethane Coatings.Waterborne polyurethane coating was synthesized by using isophorone diisocyanate（IPDI）as hard segment,polytetrahydrofuran（PTMEG）as soft segment,dimethylpropionic acid（DMPA）as hydrophilic chain extender,1,4-butanediol（BDO）as front chain extender and ethylenediamine（EDA）as rear chain extender.The structure and particle size of WPU emulsion were characterized by Fourier transform infrared spectroscopy（FTIR）,nano-particle size and potential analysis.The mechanical and thermal properties of WPU coating were characterized by water absorption test,pencil hardness agent and thermogravimetric analysis.The results show that the particle size distribution of WPU emulsion can be more uniform and the occurrence of large particles and agglomerations can be reduced by post-chain reaction.And the addition of EDA is beneficial to the improvement of WPU film water absorption,hardness and initial thermal decomposition temperature,hardness and initial thermal decomposition temperature up to H and 266.4℃.（2）Preparation and research of phosphorus-containing waterborne polyurethane flame retardant coatings.On the basis of the previous chapter,the phosphorous containing waterborne polyurethane flame retardant coating（FPU）was prepared by replacing BDO with phosphorous diol FRC-6 as prechain extender as reaction monomer.Water resistance and mechanical properties of FPU film were characterized by water absorption test and hardness test.The results show that the introduction of FRC-6 can reduce the water resistance and hardness of FPU film,and the hardness and water absorption rate are as low as B and 13.14%.The flame retardancy of FPU coating was characterized by thermogravimetric analysis and limiting oxygen index test.The results showed that the addition of FRC-6 could significantly improve the flame retardancy of WPU,with the highest LOI of 28.7%and the highest carbon residue rate of 6.34%.（3）Preparation and research of phosphorus/silicon synergistic flame retardant waterborne polyurethane coating.Firstly,A-151 silane coupling agent was prepared to modify the surface of nano-silica（A-Si O₂）to enhance the dispersion of nano-inorganic particles in polymer matrix.Phosphorus/silicon co-effective flame retardant waterborne polyurethane coating（SFPU）was prepared by co-mixing A-Si O₂ with FPU emulsion.The transmittance,water absorption and hardness of SFPU film were analyzed by uv spectrum,water absorption test and hardness test.The results show that the addition of A-Si O₂ can reduce the light transmittance of SFPU film,but can improve the water resistance and hardness of SFPU film,the water absorption rate is reduced to 9.09%,the hardness is increased to H;The flame retardancy of FPU coating was characterized by thermogravimetric analysis and limiting oxygen index test.The results showed that the addition of A-Si O₂ could further improve the flame retardancy of phosphorous waterborne polyurethane,and the LOI and carbon residue rate of SFPU increased by 0.8%and 2.35%,respectively.In this study,the effects of different flame retardants and different modification methods on the flame retardant properties of flame retardant waterborne polyurethane coatings were explored.The prepared flame retardant waterborne polyurethane coatings have good light transmittance and water resistance.The flame retardant performance also reaches the flame retardant level,which lays the foundation for its application in wood paint,building exterior walls and other fields,and promotes the research on functional modification of water-based polyurethane coatings.