Fire and termite resistance of wood treated with PF6-based ionic liquids

Six PF6-based ionic liquids (ILs) were investigated to evaluate their potential as chemicals for enhancing fire and termite resistance of wood. The ILs used in this study included 1-methyl-1-propylpyrrolidinium hexafluorophosphate ([MPPL]PF6), 1-methyl-1-propylpiperidinium hexafluorophosphate ([MPPR]PF6), 1-ethyl-3-methylimidazolium hexafluorophosphate ([EMIM]PF6), tetrabutylphosphonium hexafluorophosphate ([TBP]PF6), trihexyltetradecylphosphonium hexafluorophosphate ([THP]PF6), and 1-butylpyridinium hexafluorophosphate ([BPYR]PF6). All of the IL-treated wood samples did not undergo any morphological changes, and exhibited enhanced fire- and termite resistance compared with untreated wood. The fire resistance properties of all of the prepared IL-treated wood specimens were comparable. However, the [EMIM]PF6- and [THP]PF6-treated wood showed slightly inferior termite resistance among the tested IL-treated woods. Overall, [TBP]PF6 was the most promising candidate among the evaluated PF6-based ILs because it is stable in wood without leaching after water penetration.