Nylon-cotton blends (Nyco) has been widely used in military clothing due to the combination of good mechanical properties and comfort. However, Nyco presents a significant fire risk because the cotton fibers catch fire at relatively low temperatures (ignition point ~ 350 °C) while Nylon 66 fibers tend to melt and burn continuously adhering to the char formed by the cotton. Very few flame retardant (FR) solutions are effective for Nyco. Bio-based compounds, such as phytic acid (PA) and tannic acid (TA) have been reported to exhibit beneficial FR characteristics. PA is a naturally occurring poly-phosphoric acid while TA is an abundantly available bio-based polyphenol. PA is known to catalyze char formation of cellulose-based materials while TA forms intumescent char upon exposure to fire. Here we report a unique combination of phytic acid and tannic acid applied as coating onto Nyco that provides excellent fire resistance. PA/TA-coated Nyco fabric demonstrates self-extinguishing behavior and shortened char length (less than 10 cm) in vertical flame tests. Detailed thermal characterization using thermogravimetric analysis (TGA), pyrolysis flow combustion calorimetry (PCFC) and oxygen index measurements will be reported. Preliminary results indicate that synergistic combination of TA and PA produces intumescent char which forms the basis for the excellent fire resistance. This research opens the possibility for utilizing abundantly available bio-based phosphorus and polyphenol compounds as intumescent char forming FR coating material for textiles.

Bio-based intumescent flame retardant coating based on synergistic combination of phytic acid and tannic acid for nylon-cotton blends

254th National Meeting (2017)

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