Fire and termite resistance of wood treated with PF(6)-based ionic liquids

Six PF(6)-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]PF(6)), 1-methyl-1-propylpiperidinium hexafluorophosphate ([MPPR]PF(6)), 1-ethyl-3-methylimidazolium hexafluorophosphate ([EMIM]PF(6)), tetrabutylphosphonium hexafluorophosphate ([TBP]PF(6)), trihexyltetradecylphosphonium hexafluorophosphate ([THP]PF(6)), and 1-butylpyridinium hexafluorophosphate ([BPYR]PF(6)). 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]PF(6)- and [THP]PF(6)-treated wood showed slightly inferior termite resistance among the tested IL-treated woods. Overall, [TBP]PF(6) was the most promising candidate among the evaluated PF(6)-based ILs because it is stable in wood without leaching after water penetration.