Preparation And Properties Of Flexible Polyurethane Foam With Synergistic Flame Retarded By MoO₃ And APP

Flexible polyurethane foam(FPUF)is widely used in furniture padding,industrial packaging and other fields due to its excellent performance.However FPUF is a sort of flammable material,which produces much heat and toxic flue gas during combustion.There is a great fire risk of FPUF,consequently,it is very necessary to flame retardant FPUF.Ammonium polyphosphate(APP)is an inorganic phosphorus flame retardant,which can reduce the heat generated when the polymer burns.Molybdenum trioxide(MoO₃)has excellent smoke suppression function,but it has poor effect when used alone.In this paper,APP as flame retardant and MoO₃as smoke inhibitor were expected to form a synergistic flame retardant system.The thermal stability and flame retardant properties of FPUF were researched,and its flame retardant mechanism was discussed.The main contents of this paper are as follows:1.Flexible polyurethane foam was prepared by one-step method with isocyanate and polyether polyol as raw materials.The effects of the amount of catalyst on the foam structure,thermal stability and combustion properties of FPUF were studied.The results show that when the ratio of stannous isooctanoate to triethylenediamine is 1:1,it shows a more uniform foam structure.When the amount of the two substances is quite different,the foam will shrink or collapse.The addition of catalyst has little effect on the thermal stability and heat release of the foam.2.Flexible polyurethane foam was prepared by the adding of APP and MoO₃as synergistic flame retardants.It turns out that the APP and MoO₃slightly changed the microstructure of the FPUF.APP and MoO₃improves the thermal stability and carbon residue rate of FPUF;When the addition of APP and MoO₃was 7.5%,the peak heat release rate(pk HRR),total heat release(THR)and total smoke production(TSP)decreased by 32.32%,44.20%and 66.36%.The improvement of flame retardant performance is mainly due to the free radical capture of phosphorus containing groups,the release of CO₂,NH₃and other flame retardant gases,and the accelerated catalytic carbonization of phosphorus containing compounds,which plays a barrier role in isolating heat and oxygen.3.Using MoO₃-CS(chitosan)dispersion as cationic layer solution and APP solution as anionic layer solution,the FPUF coated with APP-MoO₃flame retardant coating was completed by layer-by-layer self-assembly technology.It turns out that the surface of the flame retardant foam is coarser,indicating that the flame retardant coating is effectively constructed on the surface of the FPUF.When the number of bilayers coating was 5,pk HRR,THR and TSP decreased by 53.84%,38.35%and 57.22%.The flame retardant mechanism was also analyzed.In the gas phase,the flame retardant coating releases free radicals and non combustible gases containing phosphorus,thus inhibiting the combustion reaction.In the condensed phase,the thermal degradation products promote the rapid dehydration of the foam surface and carbonization,and the catalytic carbon forming effect of molybdenum trioxide.The carbon layer formed can block the transmission of heat and combustible gas,and significantly reduce the fire risk of the foam.