Study On The Flame Retardant Flexible Polyurethane Foam Coated With Carboxylic Metal Complexes

Flexible polyurethane foam（FPUF）is extensively used in various industries due to its remarkable physical and chemical properties.However,FPUF is inherently flammable,resistant to self-extinguishing,and produces toxic smoke during combustion,which seriously endangers personal safety and property security.Therefore,it is of great significance to apply flame retardant treatment to it.Pyromellitic Acid（PMA）is regarded as a promising carboxylic acid ligand because of its high symmetry and ligand diversity.Copper sulfate（Cu SO₄）and copper pyrophosphate（Cu₂P₂O₇）can be used as flame retardants to catalyze the formation of carbon and effectively inhibit the flame spread.Therefore,in this thesis,a series of flame retardants were designed from the perspective of metallic element catalytic carbon formation and synergistic flame retardancy using PMA,Cu SO₄,and Cu₂P₂O₇ as raw materials to investigate their impacts on the flame retardant and smoke suppression performance and mechanical properties of FPUF.The primary work and findings are shown as follows:Using PMA and Cu SO₄ as raw materials,PMA-Cu SO₄ metal complexes were successfully fabricated by the general synthesis method via adjusting the p H values（p H=4,5,6,7）during the ligand reaction,which were subsequently constructed on the surface of FPUF by direct impregnation deposition.The results showed that the addition of PMA-Cu SO₄ metal complex had essentially low impact on the physical structure and mechanical properties of the FPUF.PMA-Cu SO₄ metal complex could not only effectively enhance the limiting oxygen index（LOI）value of FPUF,but also reduce the heat release rate and the release of smoke during FPUF combustion.In particular,when the p H was 6,the PMA-Cu SO₄ metal complex had the most effective coordination and exhibited the best flame-retardant capability.Additionally,the LOI value of FPUF@PMA-Cu6 increased to 22.4%,while its p HRR,SPR,and TSP decrease by18.45%,18.49%,and 48.23%respectively.The study of the flame retardant mechanism demonstrated that it was principally attributed to the catalytic carbon formation by metal ions,acting as a flame-retardancy in the condensed phase.Based on the above research,in order to further improve the flame retardant and smoke suppression performance of FPUF,from the perspective of synergistic flame retardancy,PMA-Cu₂P₂O₇ metal complexes with different reaction p H values（p H=4,5,6,7）were successfully manufactured using PMA and Cu₂P₂O₇ as raw materials and flame retardant FPUF was prepared.The results revealed that under similar adhesion amounts of flame retardants,the flame retardant could increase the residual carbon rate of FPUF from 0.99%to 19.43～23.36%at 900℃.In addition,the system had higher flame retardant efficiency.Especially,when the p H was 7,the PMA-Cu₂P₂O₇ metal complex had the strongest coordination effect.Besides,the LOI value of FPUF@PMA-Cu P7 was increased to 22.8%,and the p HRR,SPR,and TSP decreased by 33.13%,26.89%,and 42.12%,respectively.The research on the flame retardant mechanism indicated that such system flame retardant could release phosphorus-containing radicals and non-combustible gases during the combustion process,while thermolysis products catalyzed the carbon formation to create a dense barrier layer.Both of them worked together to inhibit the process of combustion,displaying the effect of condensed phase and gas phase synergistic flame retardant.