Synthesis Of Intercalated LRHs/MoS₂ Hybrid Materials And Study On Flame Retardant TPU

Thermoplastic polyurethane（TPU）,as a typical polymer material,has been widely used in construction,aviation,wire and cable,home appliances,automotive and other fields due to its unique physical and chemical properties.However,as a polymer,thermoplastic polyurethane material is flammable when used,and will produce a lot of smoke and toxic gases in the combustion process.Therefore,in industrial production,we usually need to add flame retardant to thermoplastic polyurethane.Hydrotalcite,as a representative of inorganic flame retardant,has received extensive attention and research in the field of flame retardant in recent years because of its green environmental protection and low price.In this paper,through one-step precipitation method,hydrothermal method and ion exchange method,rare earth La³⁺was mixed into the layer of hydrotalcite and assembled with Mo S₂ nano-sheets.Then,several different large volume anions were inserted into the layers of hydrotalcite,and several representative intercalated LRHs/Mo S₂ hybrid materials were constructed.The morphology and structure of the materials were characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,Fourier transform infrared spectroscopy（FTIR）and energy dispersive X-ray spectroscopy（EDS）.Then these materials are added into TPU in different amounts to prepare TPU composites.The flame retardant and smoke suppression properties and thermal stability of the TPU composite were investigated by using a conical calorimeter（CCT）and a thermogravimetric analyzer（TGA）.The carbon residue after combustion was analyzed to reveal the flame retardant and smoke suppression mechanism of the intercalated LRHS/Mo S₂ hybrid material.Finally,the tensile properties of TPU composites were tested to investigate the influence of these materials on the mechanical properties of TPU.XRD,SEM,EDS and FTIR test results show that the above materials all have good crystal morphology like hydrotalcite,rare earth La³⁺is successfully introduced into the lamination of hydrotalcite,Mo S₂ nanosheets are successfully hybridized with LRHs,and large volume anions are also successfully inserted into the lamination of hydrotalcite.The CCT test results show that the flame retardant and smoke suppression performance of Mo₇O₂₄^6--LRHs/Mo S₂ hybrid material is the best,the flame retardant and smoke suppression performance of SA-LRHs/Mo S₂ hybrid material is the worst,and the flame retardant and smoke suppression performance of STPP-LRHs/Mo S₂ hybrid material is between them.Compared with pure TPU,when the addition amount of LRHs/Mo S₂,Mo₇O₂₄^6--LRHs/Mo S₂,SA-LRHs/Mo S₂ and STPP-LRHs/Mo S₂ hybrid materials is 3wt%,the p HRR values of the corresponding TPU composites decreased by 62.2%,63.9%,51.8%and 59.0%,respectively;The THR value decreased by 35.4%,31.3%,15.0%and 27.6%,respectively.The p SPR value decreased by 66.3%,61.2%,60.2%and 51.3%,respectively.The TSP values decreased by 70.4%,61.2%,19.7%and 61/9%,respectively.The TGA test results showed that the thermal stability of the modified hydrotalcite on TPU was not significantly improved,which was because the modified hydrotalcite would decompose in advance at lower temperature.The results of carbon residue analysis show that the intercalated LRHs/Mo S₂material achieves the purpose of flame retardant and smoke suppression mainly through the mechanism of gas-solid phase synergistic action.The mechanism of solid phase flame retardant is that the formed carbon layer and Mo S₂ together play a physical shielding role,blocking the transfer of heat and flammable gas.The mechanism of vapor-phase flame retardant is that the material releases incombustible gas at high temperature,diluting the flammable gas,and achieving the purpose of flame retardant and smoke suppression.The tensile test results show that when the addition amount of LRHs/Mo S₂,Mo₇O₂₄^6--LRHs/Mo S₂,SA-LRHs/Mo S₂ and STPP-LRHs/Mo S₂ hybrid materials is 3wt%,the fracture strength of the corresponding TPU composites decreases by 35.3%,24.6%,8.1%,13.7%,respectively,compared with pure TPU.The elongation at break of the corresponding TPU composites decreased by 51.6%,35.3%,15.0%,26.7%,respectively.