Inorganic Treatment Agent For Rigid Polyurethane Influence Of Thermal Conductivity And Flame Retardancy

Rigid polyurethane foam is widely used in the field of thermal insulation due to its low thermal conductivity,light weight and high specific strength.However,because of its flammable hydrocarbon segments,low density and large specific surface area,it is easy to burn when exposed to open fire,producing a large amount of toxic gases and posing a fire safety hazard.Therefore,it is necessary to modify the rigid polyurethane foam with flame retardant.In this thesis,ammonium polyphosphate/zinc borate/polyurethane foam composite(APP/ZB/RPUF)was prepared by solution mixing method.The effect of flame retardants addition on the porous structure,thermal conductivity and flame retardancy of composites were studied.Then,kh-Si O₂was introduced into APP/ZB/RPUF system.The effects of kh-Si O₂on the thermal conductivity,flame retardancy and combustion behavior of APP/ZB/RPUF were systematically investigated.The synergistic effects and flame retardancy mechanisms between APP,ZB and Si O₂were elucidated.The results show that the thermal conductivity of APP/ZB/RPUF composites decreases with the addition of flame retardant.When the amount of flame retardant reaches 40 phr,the thermal conductivity is 0.0438 W/(m k).The flame retardant properties of APP/ZB/RPUF composites shows that there is a synergistic effect between APP and ZB in flame retardant properties.When the total amount of APP and ZB is 20 phr and the ratio of APP to ZB is 9:1,the most obvious effect in synergistic flame retardant polyurethane was shown.Compared with the composites without ZB,the limiting oxygen index of APP/ZB/RPUF composites reached 23.5.The maximum heat release rate p HRR decreased by 54.4%.The maximum total smoke release TSR decreased by 22.89%and the carbon residue increased by 22.14times(up to 28.13%).The analysis of morphology and composition of carbon residue after combustion of APP/ZB/RPUF composites shows that the synergistic flame retardant mechanism between APP and ZB is that the Zn O and B₂O₃produced by ZB decomposition can increase the strength of carbon layer,and then increase the final carbon residue,which in turn induced smoke suppression and flame retardant.On the basis studying of the synergistic flame retardancy of APP and ZB on polyurethane,silane in-situ modified hollow silica(kh-Si O₂)was introduced to the system.and the thermal conductivity and flame retardancy of ammonium polyphosphate/zinc borate/silane in-situ modified hollow silica/polyurethane foam composite(APP/ZB/Si O₂/RPUF)were systematically studied.Research on thermal conductivity shows that the addition of kh-Si O₂can effectively reduce the thermal conductivity of the composite.When the amount of kh-Si O₂is 3 phr,the thermal conductivity of the composite can be reduced to 0.0319 W/(m·k).The LOI and vertical combustion tests show that the LOI of the composite can reach 28.5(flame retardant level)with a small amount of kh-Si O₂(3 phr),and the vertical combustion can reach UL-94 V-0 level.Cone calorimetry data show that the addition of kh-Si O₂has obvious toxic and smoke reducing effects on APP/ZB/Si O₂/RPUF composite.When the amount of kh-Si O₂is 3 phr,the toxic gas generation index decreases by76.25%(only 0.38 g/s),and the maximum smoke release rate decreases by 29.3%(0.0372 m~2/s).The results of char residue after combustion show that kh-Si O₂can promote the formation of char layer,increase the strength of char layer and enhance the barrier effect on heat and mass.