Two-Step Polyelectrolyte Complex Coating for Flame Retardant Flax
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abstract
AbstractFlax fabric textile is of great interest as biofiber reinforcement in composites, which has gained popularity due to the high demand for sustainable materials. Despite its sustainability, flax is inherently flammable. This study demonstrates a twostep polyelectrolyte complex (PEC) coating that renders flax fabric selfextinguishing. The PEC coating consists of polyethylenimine (PEI) and sodium hexametaphosphate (PSP), cured with a citric acid buffer. Sonication employed during the curing process improves the infiltration of the coating into the flax fibers and maintains the fabric's hand. When comparing nonsonicated and sonicated flax samples, the latter achieves selfextinguishing behavior and passes the vertical flame test. Pyrolysiscombustion flow calorimetry reveals that this PEI/PSP coating (with sonication) reduces the peak heat release rate and total heat release by 40% and 67%, respectively. The intumescent mechanism is predominantly observed in the condensed phase, as suggested by differential scanning calorimetry and Xray photoelectron spectroscopy. The results demonstrate that the twostep PEC treatment with sonication effectively reduces the flammability of flax fabric, making it a promising option for the development of functional fibers, particularly for biocomposite reinforcement.
