Theoretical and experimental studies on the thermal decomposition of 1-butyl-3-methylimidazolium dibutyl phosphate

Ionic liquid, an organic molten salt, has efficient flame-retardant performance. Few researchers have attempted to study its flame-retardant mechanism. Moreover, thermal stability and pyrolysis products have a great impact on the flame retardancy. Therefore, this paper focused on the phosphate ionic liquid of 1-butyl-3-methylimidazolium dibutyl phosphate ([Bmim][DBP]) and analyzed its thermal decomposition products and characteristics. The major bond energies of [Bmim][DBP] were calculated using B3LYP/6-311++G(d,p)//M06-2X/6-311++G(d,p) level. The experimental results show that the pyrolysis products were as followed: alkane or alkene with a carbon chain length of 1-4; imidazole and its derivatives; esters. Furthermore, Gas chromatography-mass spectrometer and Fourier transform infrared spectrometer were utilized to measure the gaseous products and solid phase products of [Bmim][DBP], which were obtained during thermogravimetric analysis. The results of theoretical and experimental analysis were highly consistent. Finally, the possible flame-retardant mechanism of [Bmim][DBP] was proposed.