| Composite membranes were prepared by dipping method, using domestic perfluorinated sulfonic acid ion-exchange membrane as matrix doped 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid ([BMIM]BF4). The ionic liquid’s structure was analyzed by ATR-FTIR and mass spectrometry. The thermal stability properties of ionic liquids were investigated by isothermal and non-isothermal thermogravimetry methods. The composite membranes were characterized by the ATR-FTIR, DMA and TG-DTG methods. The impact of various solvents on the performance of the composite membranes were investigated. The temperature resistance of composite membranes were investigated by the TGA method. The proton conductivity of composite membranes were investigated by Using of the impedance conductivity. And the thermal life equation of composite membranes calculated by isothermal TGA, the possible thermal degradation kinetic equation and its mechanism were deduced.Thermal decomposition kinetics of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) were investigated, using isothermal and non-isothermal thermo-gravimetric analysis. The results indicated that the average apparent activation energy of thermal degradation obtained by different methods is 105.6kJ/mol. Isothermal test in the air showed that after heated at 180 and 300℃ for 10h, the conversion rate of ILs were 1.28 and 2.57% respectively. When less than 300℃, all bands of IR. spectra nearly unchanged. It suggests that [BMIM]BF4 basically is stable. When heated at 350℃ for 2h, the ATR-FTIR spectroscopy show that the relative intensity of BF4-anion near band of 1058 cm-1 fell by 36.7%. Due to the intensity of the absorption band declined significantly in the range of 300～350℃, [BMIM]BF4 is instability, and the anion of BF4- was firstly dissociated by the action of air and heat,ionic liquids/trithylamine/Perfluorinated sulfonic acid composite membranes were synthesized of. The TGA results shows that the thermal degradation process of original membrane is divided into two phases, the first peak temperature is between 311 and 375℃, the second peak temperature is between 375 and 552℃. The composite membranes A in methanol medium only have one stage of decomposition and the peak temperature is near 405℃. The composite membrane B in water medium have three stage of decomposition, the first peak temperature is between 300 and 375℃, the second peak temperature is between 375 and 445℃, and the third peak temperature is between 445 and 700℃. The TGA analysis shows that the decomposition temperature and the peak temperature of the composite membranes are moved to the high-temperature region. Thermal stability of composite membrane in the aqueous medium is higher than that in the methanol medium。Comparing to original membrane, a significant change were occurred by using the ATR-FTIR spectra. The characteristic peaks of ionic liquids of the composite membrane A was born at 1052cm-1, and the composite membrane B is also. The 20% ILs-TEA-PFSA composite membranes B by using a muffle furnace thermostat test showed that, after 260 and 300℃ 10h the IR unchanged. High thermal stability of the composite membranes B was indicated.The conductivity of membrane was determinedby AC impedance method, the results show that when the temperature rose from 30℃ to 90℃, the electrical conductivity of composite membrane A which containing 5,10,15 and 20% ionic liquid is between 0.92×10-5～3.52×10-5S·cm-1, the electrical conductivity of composite membrane B is between 0.59×10-5～2.38×10-5S·cm-1, and the conductivity of PFSA membrane is 0.30×10-5～1.21×10-5S·cm-1, the conductivity of composite membrane is increased 2-3 times than that of PFSA membrane. The conductivity of membrane increases with the rise of temperature. The electrical conductivity of the composite membrane B and PFSA film were determined in range of -25～0℃. The activation energy E of the composite membrane A and B were obtained between 1.62～2.47kJ/mol andl.66～1.87kJ/mol by means of the Arrhenius equation.The thermal degradation kinetic parameters and mechanism function were obtained by analyzing the non-isothermal data of the composite membrane, and by using the Kissinger, Flynn-Wall-Ozawa, Starink, Friedman methods. |
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