Bio-sourced Intumescent Nanocoating

Nylon–cotton blended fabric (NYCO), commonly used in military uniforms and workwear for its comfort and resilience, presents an inherent fire risk due to its high flammability and high heat release. There are few effective flame retardant treatments for NYCO that are environmentally benign and maintain the hand of the fabric. To solve this problem, a layer-by-layer (LbL)-assembled 15 quadlayer (QL) coating, consisting of chitosan (CH), phytic acid (PA), and tannic acid (TA), is applied to NYCO. Individually pairing TA or PA with CH is not self-extinguishing, but they work synergistically in the QL system to create an effective intumescent coating. This completely bio-sourced, water-based coating self-extinguishes in a vertical flame test (ASTM D6413), with only 16.6% weight added to NYCO, yielding 91% postburn residue and a 51% decrease in peak heat release rate. This novel coating provides an opportunity to replace environmentally questionable flame retardant treatments with a fully sustainable system.

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D. L. Smith, N. A. Vest, D. Rodriguez-Melendez, B. Palen, J. C. Grunlan, Advanced Engineering Materials, 2022, in press.