Construction Of Hybrid Flame Retardants And Their Effects On Flame Retardancy,Smoke Suppression And Mechanism Of Flexible Polyurethane Foam

Flexible polyurethane foam(FPUF)is a cushioning material that exhibits excellent performance.However,due to its open-cell structure and chemical composition of carbon,hydrogen,and oxygen elements,FPUF is highly flammable and generates a large amount of toxic and harmful fumes.This thesis is oriented to the safety requirements of cushion materials,aiming at the fire hazards of FPUF used for cushions in closed and confined spaces that release a large amount of heat and toxic fumes during pyrolysis and combustion,combining essential flame retardancy,nanocomposites,and catalytic charcoal formation as well as the coupling mechanism of catalytic detoxification,several intrinsic flame retardant polyurethane-based soft foam seat cushion materials were prepared.This study aims to investigate the impact of flame retardant polyols and multi-dimensional hybrid catalytic synergists on the pyrolysis process of FPUF composites.The formation and evolution of pyrolysis products will be analyzed under different pyrolysis conditions to explore the pyrolysis mechanism.Additionally,the combustion behavior of FPUF composites will be studied under various combustion conditions,and the combustion heat release,smoke generation,and changes in the charcoal layer will be analyzed.This is for the application of high-performance seat cushion materials made from FPUF.(1)The study investigated the impact of La2Sn2O7,a rare earth compound with a pyrochlore structure,on the flame retardancy and smoke suppression properties of FPUF composites when incorporated into the three-dimensional bulk hybrid material LaAPP.Firstly,La2Sn2O7 with a pyrochlore structure was prepared through a hydrothermal reaction of La(NO3)3.6H2O and SnCl4.5H2O.Next,La2Sn2O7 was deposited onto the surface of APP using KH550 silane hydrolysis to form a threedimensional block with a core-shell structure.LaAPP is a hybrid material that was then added to FPUF during the foaming stage to create a hybrid-modified FPUF composite.The research results show that the fire risks associated with FPUF composite materials,such as heat,smoke,and toxic gases,are significantly reduced.Through the analysis of the cone test results,it can be found that modifications to FPUF resulted in significant improvements.Compared to unmodified FPUF,the modified version showed reductions in pHRR(37.5%),THR(25.9%),PSPR(33.3%),TSP(38.2%),and PCO(38.5%).Additionally,a reduction in PCO2(39.4%)was achieved.Through the analysis of TG-IR results,it can be observed that toxic and harmful gases or groups,such as CO2,CO,C=O,NO,NO2,etc.,have been reduced to varying degrees.Raman spectroscopy and digital photographs indicate the formation of dense carbon deposits.Based on this,a mechanism for flame retardancy and smoke suppression is proposed.La2Sn2O7,with a pyrochlore structure,can act as a catalyst in the combustion process of FPUF composites.It can also inhibit the release of toxic gases and smoke while improving the quality of the resulting carbon residue.Through a simple modification of the interface,abundant rare earth mineral resources in China can be utilized as a smoke suppressant and phosphorus-containing flame retardant APP to create a synergistic effect.This can be applied to the FPUF system,providing a significant opportunity for the development of high-fire-safety polymer composites.(2)The study investigated the impact of a two-dimensional hybrid sheet flame retardant and smoke suppressant,ZIF-8@Ti3C2Tx,on the flame retardant and smoke suppression properties of FPUF composites.First,two-dimensional sheet material MXenes were prepared through LiF/HCl etching.Then,using the in-situ coprecipitation method,ZIF-8 was deposited on the MXenes with a large relative area to form a two-dimensional hybrid sheet flame retardant and smoke suppressant,ZIF8@Ti3C2Tx.Finally,ZIF-8@Ti3C2Tx was added to FPUF at different proportions during the foaming stage to form a flame retardant and smoke suppressant-modified two-dimensional hybrid sheet FPUF composite.Subsequently,the heat and smoke particles of the FPUF composite were tested and analyzed using cone calorimetry,TGIR,and other characterization methods.The results showed that compared to pure FPUF,the hybrid modified FPUF composite material had a 46%reduction in pHRR and a 68%reduction in THR.In addition,the tensile and compressive strengths of the hybrid-modified FPUF composites were increased by 52%and 130%,respectively.Afterward,the flame-retardant mechanism was proposed through the analysis of carbon residue and combustion conditions.The excellent bimetallic catalytic carbonization effect and physical barrier effect of the two-dimensional sheet hybrid material ZIF8@Ti3C2Tx were confirmed.Therefore,this study presents a straightforward and dependable approach to fabricating flame-retardant and smoke-suppressant FPUF composites that exhibit improved mechanical and fire safety properties.(3)To address the challenge of limited improvement in the flame retardancy of nano-hybrid materials,such as LOI and VBT tests,this study aims to enhance the dispersion ability of hybrid materials in FPUF.Additionally,the study aims to investigate the performance of multi-element synergistic flame retardants and smoke suppressants.To achieve this,organosilicon and phenyl phosphorus compounds were synthesized through in-situ polymerization and grafted onto Ti3C2Tx to form a twodimensional hybrid sheet flame retardant and smoke suppressant,Ti3C2Tx@BPA@PCL.Based on the research findings on phosphorus-containing flame retardants in Chapter 2 and considering the issue of dispersion,we synthesized a DOPO-based phosphorus-containing polyol flame retardant,DH-DOPO.DH-DOPO,along with Ti3C2Tx@BPA@PCL,was added to FPUF to prepare flame-retardant and smoke-suppressant FPUF composites.Compared to pure FPUF,the addition of Ti3C2Tx@BPA@PCL and DH-DOPO reduced the pHRR and THR by 36.1%and 44.0%,respectively.Additionally,the PCO2 and PCO were reduced by 40.3%and 52.1%,respectively.The FPUF composite exhibited self-extinguishing properties and passed the Vertical Burning Test(VBT).Further studies have revealed that the tensile and compressive strengths of FPUFs were enhanced by 24.0%and 253%,respectively,due to the rigid structure of Ti3C2Tx@BPA@PCL.In addition,the fatigue resistance of the FPUF composites was significantly enhanced during cyclic testing.