Investigations into the Mechanisms of Flame Retardation on Wool

Abstract

A number of flame-retardant systems have been applied to wool, and their flame-inhibiting efficiencies in atmospheres containing oxygen and nitrous oxide have been compared in order to explore the mechanisms by which they operate. The retardant systems investigated include phosphoric acid, sulfuric acid, sulfamic acid, and their ammonium salts, hexafluorophosphate, borax, boric acid, fluoroborate, antimony oxide/hydrochloric acid, hexafluorozirconate, hexafluorotitanate, hexafluorostannate, and dichromate. Most of the systems apparently operate in the solid phase though by different mechanisms. The antimony-based system inhibits in the gas phase. The chromium system, as well as catalyzing the thermal decomposition of wool, also inhibits gas-phase reactions, probably by a heterogeneous mechanism. Fluorostannate when padded onto wool also exhibits gase-phase inhibition properties, but when exhausted onto wool it appears to inhibit in the solid phase. The fluorotitanate treatment shows a dependence on the nature of the oxidizing atmosphere, but this may be due to the fact that a metal oxide-oxygen species complex is necessary for retardation. Fluorozirconate does not show the same dependence, though it is closely related chemically to the fluorotitanate system. A preliminary investigation has been made into the effectiveness of combinations of the padded fluorozirconate system with the sulfamic acid, fluoroborate, boric acid, and antimony oxide/hydrochloric acid systems.