Flame Retardant Tpu With Several Metal-organic Framework Compounds As Synergisms

In this paper,copper nitrate,cobalt chloride,ferric chloride,yttrium chloride and1,3,5-benzene tricarboxylic acid were used as raw materials to prepare four kinds of MOFs materials(MOF-Cu,MOF-Co,MOF-Fe,MOF-Y).The flame-retardant TPU composites using MOFs as synergisms were prepared.Then the combustion performance and thermal stability of TPU composites were studied by the cone calorimeter test(CCT),scanning electron microscope(SEM),Raman spectroscopy(LRS),X-ray photoelectron spectroscopy(XPS),micro calorimeter(MCC),and thermogravimetric-infrared combined use(TG-IR),respectively.The specific research content is as follows:(1)Synergistic flame retardant TPU based on APP and MOF-Cu APP.It had been found that MOF-Cu had good synergistic flame retardant and smoke suppression properties for TPU/APP composites.The peak heat release rate(p HRR)of the TPU/APP sample was 270.7k W/m²,and the total smoke release(TSR)was498.2m²/m².The p HRR value of TPU/APP/Cu_0.25sample was reduced to 216.6k W/m²,and the TSR value of TPU/APP/Cu_0.0625was reduced to 330.3m²/m².MOF-Cu can increase the char layer of TPU composites.The char layer of TPU/APP/Cu_0.0625reached 55.8wt%,which was much higher than the TPU/APP sample(17.8wt%).(2)Synergistic flame retardant TPU based on APP and MOF-Co APP.It had been found that MOF-Co can improve the expansion and compactness of the char layer of the TPU/APP system,and improved the mechanical properties of the system.MOF-Co can reduce the thermal hazard of TPU composites.The p HRR value of TPU/APP/Co_0.5reduced to 239.1k W/m²,which was 11.7%lower than that of TPU/APP(270.7k W/m²).The expansion degree of the char layer was increased.The height of the char layer of TPU/APP/Co0.5 reached 4.8cm,which was 1.5cm higher than that of TPU/APP;the char layer content of TPU/APP/Co0.5 was the highest(61.4wt%).The surface of the char layer was complete and the degree of graphitization was improved.MOF-Co increased the breaking strength of TPU/APP/Co_0.25to 14.3MPa,which was improved significantly compared to the TPU/APP sample(13.2MPa).(3)Synergistic flame retardant TPU based on APP and MOF-Fe.It had been found that MOF-Fe had a positive effect on improving the smoke suppression performance of the TPU/APP composites.TPU/APP/Fe_0.25had the lowest TSR value of 224.2m²/m²,which was 55.0%lower than the TPU/APP(498.2m²/m²).In addition,MOF-Fe improved the thermal stability of the composite material,and the char layer mass of TPU/APP/Fe_0.25still reached 25.89wt%at 700°C.(4)Synergistic flame retardant TPU based on APP and MOF-Y.It had been found that MOF-Y can improve the structure and the degree of graphitization of the char layer.The p HRR value of TPU/APP/Y_0.125was reduced to 184.5k W/m²,which was31.8%lower than that of TPU/APP,and THR value was reduced to 48.8 MJ/m²,which was 58.2%lower than that of TPU/APP.TPU/APP/Y_0.25had the highest char layer content(46.0wt%).The char layer was continuous and complete with many protrusions on the surface,and a large number of fine particles were observed at the microscopic level.The I_D/I_Gvalue was reduced to 0.95,and the content of graphite carbon was increased.In summary,MOFs can improve the fire safety of TPU.MOFs can reduce the heat hazard and smoke hazard,and improve the thermal stability by improving the structure of the char layer,enhancing the amount of charbon,increasing the compactness and expansion of the char layer.MOFs have good application prospects in synergistic flame-retardant TPU.