Synthesis and combustion inhibition efficiency of iron short-chain perfluorocarboxylates

By Y Koshiba, Y Tsunokuma, and H Ohtani
Fire Safety J
October 5, 2020
DOI: 10.1016/j.firesaf.2020.103224

This study reports an experimental exploration of the combustion inhibition efficiency of iron short-chain perfluorocarboxylates, namely, iron trifluoroacetate (FeTFA) and iron pentafluoropropionate (FePFP). The aim is to develop a new phosphor-free fire-extinguishing agent. The synthesized FeTFA and FePFP were characterized by ultraviolet–visible spectroscopy, Fourier-transform infrared spectroscopy, X-ray fluorescence measurements, and fast-atom bombardment mass spectrometry. The FeTFA and FePFP ligands (i) coordinate with the iron ions in bridging form via carboxylate oxygens, (ii) contain no Cl⁻, and (iii) are hexanuclear complexes with chemical formulas of C18F27O22Fe6 and C27F45O22Fe6, respectively. Suppression trials and thermogravimetric measurements revealed that (i) both FeTFA and FePFP have higher combustion inhibition ability at lower suppressant concentrations than ammonium dihydrogen phosphate (an active component in conventional fire-extinguishing agents), (ii) FePFP is remarkably more inhibition-efficient than FeTFA, and (iii) neither FeTFA nor FePFP hinder cellulose pyrolysis and char combustion in the condensed phase. Thermogravimetry–mass spectrometry measurements confirmed that (i) the main decomposition product of FeTFA and FePFP is CF3, and (ii) FePFP is a better CF3 generator than FeTFA. The different inhibition abilities of the two complexes were attributed to their different CF3 generation abilities and eases of decomposing the complex.

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