Synthesis And Application Of Self-crosslinking And Flame-retardant Waterborne Polyurethane

In recent years,there has been a rising trend in fires caused by textiles.The demand for flame-retardant textiles is increasing both at home and abroad.At present,halogenated flame retardant mixing with waterborne polyurethanes are widely used to finish textile materials by coating,which has the disadvantage of large usage of flame retardant,coating opacity,poor water resistance,easy migration and poisonous gases and thick smoke while burning.The inherent flame-retardant waterborne polyurethanes can overcome these shortcomings and significantly improve the flame retardancy of fabric coating.However,most flame-retardant modified waterborne polyurethanes are linear thermoplastic and single functional polymers and have many shortcomings on textiles,such as poor water and solvent resistance,low molecular weight and poor mechanical properties.To solve these problems,this project firstly synthesized a kind of polyether diol containing phosphorus and nitrogen(PNFR).Then it reacted with isophorone diisocyanate and dimethylol propionic acid.At the same time,dihydroxyacetone was used as the crosslinking monomer.When modified waterborne polyurethane was emulsified,adipic dihydrazide was added and Ketone-hydrazine reaction was introduced to prepare a novel self-crosslinking and flame-retardant waterborne polyurethane(SFR-WPU).Afterwards,SFR-WPU as finishing agent was coated onto polyester fabric.The crosslinking reaction between ketone and hydrazine was used to reduce the finishing temperature of polyester fabric and save energy consumption.Besides,the synergistic effect of phosphorus-nitrogen elements in the finishing agent could provide polyester fabric with excellent flame-retardancy.The research contents and results were as follows:(1)a kind of polyether diol containing phosphorus and nitrogen(PNFR)was synthesized by transesterification condensation reaction,using dimethyl phosphonate(DMMP)and diethanolamine(DEA)as raw materials,dibutyltin dilaurate(DBTDL)as catalyst.The optimized synthesis conditions of PNFR were as follows:n(DMMP):n(DEA)=1:1.4,the reaction temperature and time were 150 ? and 5 h,respectively,the dosage of DBTDL was 0.5%of the total mass of reactants;Under the optimized synthesis conditions,the physical and chemical properties of PNFR were as follows:the yield of PNFR was 89%,the relative molecular weight is 1046,the hydroxyl value is 160 mgKOH/g,the acid value is 1.8 mgKOH/g and the color was light yellow viscous liquid.(2)The self-crosslinking and flame-retardant waterborne polyurethane(SFR-WPU)was successfully synthesized by prepolymer method using isophorone diisocyanate(IDPI),polyether diol containing phosphorus and nitrogen(PNFR)as raw materials,dimethylol propionic acid(DMPA)as hydrophilic monomer,dihydroxyacetone(DHA)as crosslinking monomer and triethylamine(TEA)as salt forming agent.The optimized synthesis conditions of SFR-WPU were as follows:n(IPDI):n(DHA)=2.4:1,the reaction temperature and time were 80? and 4 h,respectively,the dosage of DMPA was 5%of the total mass of reactants,the neutralization degree was 110%and n(DHA):n(ADH)=1:1.1;Under the optimized synthesis conditions,SFR-WPU emulsion had excellent dispersion and stability.The particle size,dispersion coefficient(PDI)and zeta potential of SFR-WPU emulsion were 79.29 nm,0.269 and-50.4 mV,respectively.(3)SFR-WPU was used as finishing agent to finish polyester fabric by coating technology.The optimized finishing process was as follows:the drying time was 60 s,drying temperature was 120?.The limiting oxygen index(LOI),afterflame time,afterglow time and damaged length of SFR-WPU finished polyester fabric were 28.4%,4.66 s,0 s and 10.9 cm,respectively,which obtained Class B1 of National Standard GB/T 17597-2006 and indicated that the finished polyester fabric had excellent flame-retardant properties.(4)It can be found from SEM-EDS images that SFR-WPU has been successfully finished onto the polyester fabric with obvious film-forming and phosphorus and nitrogen elements were evenly distributed on the surface,providing polyester with fabric good P/N synergistic flame retardancy.According to the TG curves,the initial decomposition temperature of the finished fabric decreased from 370 to 260?,but the residual carbon increased from 16%to 21%,indicating that SFR-WPU had excellent carbonization effect.In addition,MCC and DS tests showed that finished polyester fabric had low heat release and excellent smoke suppression performances,which was of great significance for flame-retardant textiles and fire rescue.