Research On Fire Safety Design And Mechanism Of The Synergism Of Copper Chelate In Intumescen Flame Retardant TPU

Copper chelates are a complex with a central atom of copper,and the copper,as a member of transition metals,is hot in flame retardant applications.Thermoplastic polyurethane?TPU?is widely recognized as a new type of polymer material that is environmentally friendly and excellent in performance.It has high strength,high tensile strength,good plastic toughness,wear resistance and oil resistance,and has better elasticity than other polyurethane materials.However,it's flammability,a large amount of smoke generation when burnning.At the same time,dripping of molten material is easily cause the combustion of other flammable materials.Therefore,improving the fire safety of TPU has become a difficult problem to be overcome in many fields.The traditional intumescent flame retardant has the disadvantages of large amount of addition and destroying the original mechanical properties.Therefore,it is the focus of this paper to explore a new type of synergistic intumescent flame retardant and improve the fire safety of TPU.In view of the above problems,four copper chelates were synthesized in this paper,namely copper salicylaldehyde?CuSA?,copper salicylaldehyde oxime?CuSAO?,copper fumarate?fu-Cu?,and copper imidazole?Im-Cu?.Copper chelate and ammonium polyphosphate?APP?constitute a synergistic expansion flame retardant system.TPU with fire safety performance was prepared and its flame retardant mechanism was studied.In this paper,the Cone Calorimeter?CCT?,Limiting Oxygen Index?LOI?,Smoke Density Test?SDT?,Micro Calorimeter?MCC?,X-ray photoelectron spectroscopy?XPS?,Thermogravimetric Analysis?TGA?,and Thermogravimetry-Combined infrared?TG-IR?and other testing methods to study the combustion performance and thermal stability of TPU composite samples.The combustion performance was shown in the TPU-APP-CuSA system:The CCT test results showed that the pHRR in the TPU-APP sample was 161.9 kW/m²,and the CuSA1 sample droped to 128.1 kW/m².The SDT test results showed that the luminous flux increased from 5%To 35%.In the TPU-APP-CuSAO system:CCT test results showed that CuSAO prolonged the ignition time of TPU composites,and the ignition time of CuSAO2 samples was extended to 290 s.Compared with the TPU-APP sample,the pHRR of CuSAO1 sample decreased by 18%,THR decreased by 42.5%,TSR decreased by 58%,and the quality of residual carbon increased.In the TPU-APP-fu-Cu system:The CCT test results showed that compared with the TPU-APP sample,the THR of the fu-Cu2 sample decreased by 32.6%,and the TSR decreased by 55.7%.In the TPU-APP-Im-Cu system:the ignition time of the Im-1 sample is the shortest,and the CO and CO₂ emissions of the Im-2 sample were reduced.The THR of the TPU-APP sample was 46 MJ/m²,the THR value of the Im-1 sample was 25.6 MJ/m²,and the TSR value of the Im-1 sample was 271.6 m²/m².Compared with TPU-APP samples,the TSR value decreased by 64.8%.Thermal stability through TGA,MCC and other test results showed that the four copper chelates had good thermal stability and had specific structures,including aromatic rings,conjugated structures,etc.,which played different roles,improving the thermal stability of TPU.After four series of samples were subjected to combustion tests,it was found that the carbon layer had a higher swelling degree and the carbon layer were stronger.And the intermediate products or non-flammable gases released by the material itself were reduced,which effectively curbed the release of harmful smoke particles.The research of this subject provides new ideas for flame retardant TPU.