Preparation,Combustion Performance Study And Simulation Application Of Flame Retardant Polyurethane Rigid Foam

At present,the national government at all levels attaches great importance to building energy saving,and increase the research and development in the field of building insulation.Rigid polyurethane foam（RPUF）is a common building exterior insulation material,which has the advantages of low thermal conductivity,light mass and good mechanical properties.However,RPUF itself is flammable,releasing a large amount of heat energy in a short period of time and producing toxic gases,such as CO,NO_Xand HCN.There are numerous fires caused by polyurethane materials,resulting in huge casualties and economic losses,therefore,it is necessary to improve the flame retardant performance of RPUF and reduce its fire risk.In this article,ammonium polyphosphate（APP）as flame retardant and phosphomolybdic acid（PMA）or ionic liquid（IL）as co-effector are added to RPUF and the combustion performance and thermal stability of flame retardant RPUF are studied to investigate the influence law of flame retardant and co-effector on the thermal decomposition behavior,flame retardant performance,microscopic morphology and mechanical properties of polyurethane,and to explore its flame retardant mechanism.Meanwhile,in order to meet the demand for sustainable development of resources,this article synthesizes biodegradable biomass flame retardants using starch and replaces part of polyol for the preparation of flame retardant RPUF,and explores its flame retardant mechanism on polyurethane hard foam through combustion and thermal performance tests.In order to further study the role of flame retardants in reducing the fire risk of materials,new materials were defined in fire simulation software（Pyro Sim）based on experimental data such as thermogravimetric analysis tester（TG）and cone calorimeter（CONE）,and the actual application scenarios of flame retardant polyurethane were simulated to analyze the fire spread trend and temperature change.The details are as follows（Ⅰ）PMA with APP flame retardant RPUF were prepared by a one-step method,and the flame retardant properties,thermal stability properties and flame retardant mechanism aspects of the material were analyzed by vertical combustion tester（UL-94）,thermogravimetric-infrared（TG-IR）,CONE and TG.The experimental results showed that 15wt%APP added to polyurethane（PU/15APP）could make the system pass UL-94 V-1,while 12wt%APP and 3wt%PMA added（PU/12APP/3PMA）could pass the V-0 level test;the residual carbon amount of PU/12APP/3PMA at 800℃was 69.16%higher than that of PU/15APP under air atmosphere.The results of TG-IR analysis show that the presence of PMA reduces the generation of decomposition products such as CO₂,C-H,-C-O and benzene ring,and also makes the system release more water molecules and reduce the heat around the system.the addition of PMA makes the flame retardant polyurethane form a more stable carbon layer and reduces the fire hazard.（Ⅱ）15wt%APP and IL（1-butyl-2,3-dimethylimidazolium tetrafluoroborate,B₄F for short）were added to polyurethane hard foam,and the flame retardant and thermal stability of the materials were evaluated by UL-94,LOI,CONE and TG tests,while the char layer of the materials after combustion was subjected to scanning electron microscopy（SEM）,Raman and X-ray（XPS）.The experimental results showed that the addition of 1wt%B₄F to flame retardant polyurethane（RPUF/14APP/1B₄F）could improve the vertical combustion test of flame retardant polyurethane from V-1 level to V-0 level,and could improve the ratio of amorphous carbon to graphitic carbon（I_D/I_G）in the char layer after combustion from 1.38 to 2.68,which indicated that B₄F could improve the graphitization of the material;XPS The results showed that the C/O ratio in the residual carbon of RPUF/15APP was 1.84,and the ratio of C/O element content in the carbon layer of RPUF/14APP/1B₄F system was as high as 3.03,which indicated that B₄F could enhance the oxidation resistance of the flame retardant material.The char formation of RPUF/14APP/1B₄F was 21.24%at 800℃under air atmosphere,which was 71.01%higher than that of RPUF/15APP,and the interaction between B₄F and APP could form a more stable char layer structure in polyurethane.It is clear from the combined test results that APP and B₄F can play a good synergistic role in promoting carbon formation in flame retardant polyurethane.（Ⅲ）Amino starch phosphate was successfully synthesized using starch,phosphoric acid and urea,and characterized using infrared spectroscopy test（FT-IR）,XPS and X-ray diffractometer（XRD）,and also added to polyurethane to prepare flame retardant polyurethane hard foam,and evaluated the flame retardant performance of the material by UL-94,LOI,CONE and TG tests and The flame retardant performance and thermal stability performance of the material were evaluated by UL-94,LOI,CONE and TG tests.Raman and XPS tests were conducted to analyze the carbon layer after the combustion of CONE to explore the flame retardant mechanism of the biomass flame retardant in the condensed phase,and TG-IR tests were conducted to explore the flame retardant effect of the gas phase products of the pyrolysis process on the polyurethane.The experimental results show that the addition of 15wt%biomass flame retardant（PU-15）can make the system pass the UL-94 test with V-0 level and the LOI reaches 22.8%;the CONE test results show that the addition of amino starch phosphate can reduce the p HRR,THR,TSR and CO₂emission of the material,and the p HRR of PU-15 decreases by 36.54%compared with PU.At the same time,amino starch phosphate can also reduce the amount of various combustible small molecules generated during the combustion of the system,forming more protective carbon layer;Raman test shows that the I_D/I_Gof PU-15 is lower than that of PU,indicating that the flame retardant can increase the stability of the carbon layer.Comprehensive test results show that starch phosphate ester is an excellent flame retardant for polyurethane hard foam.（Ⅳ）Based on the results of TG and CONE tests,a new material is defined in Pyro Sim to simulate the fire propagation trend and temperature change of polyurethane hard foam when it burns under actual application scenarios.The simulation selects representative PU and PU/15APP to spread all over the standard room with fire power of 1000W,and simulates the fire spread trend and temperature and CO gas change in the room within 800s of the fire.From the simulation results,it can be seen that at158.2s,PU doorway material began to burn out and disappear,PU/15APP compared to PU delayed 107s;whether it is the roof or doorway thermocouple,the temperature of PU/15APP is lower than that of PU,and the burning time is delayed,which increases the rescue escape time.In this paper,in order to reduce the fire hazard of polyurethane rigid foam when it burns,flame retardant and co-effector as well as synthetic biomass flame retardant are added to prepare flame retardant PU,and their related performance is tested.The actual combustion scenario of polyurethane was also simulated using Pyro Sim software.The experimental data and simulation results together show that flame retardants can significantly reduce the fire hazard of polyurethane,which provides a reliable basis for studying the application of flame retardants in the actual fire scenario of polyurethane.Figure[62]table[33]reference[109]...