Grafting of phosphorus flame retardants on flax fabrics: Comparison between two routes

Flax fabrics were modified through two grafting methods in order to improve their flame retardancy. Vinyl phosphonic acid was used to treat flax fabrics via a condensation reaction between phosphonic acid function and flax hydroxyl groups. It was also grafted under radiation conditions taking advantage of its carbon-carbon double bond. Grafting efficiency of each method was assessed by X-ray fluorescence and scanning electron microscopy. The effect of the phosphorus grafting on fire behavior was studied using thermogravimetric analysis, pyrolysis combustion flow calorimetry and a preliminary fire test. In all cases, the diffusion of the phosphorus molecules into the elementary fibers bulk was observed. Phosphorus content reached 1.4 wt% using radiation grafting, leading to self-extinguishing fabrics.