CHEMICAL MODIFICATION OF COTTON FOR VALUE ADDED APPLICATIONS
Location: Cotton Chemistry and Utilization Research
Title: Intumescent all-polymer multilayer nanocoating capable of extinguishing flame on fabric
Submitted to: Advance Materials
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 29, 2011
Publication Date: September 8, 2012
Citation: Li, Y., Mannen, S., Morgan, A.B., Chang, S., Yang, Y., Condon, B.D., Grunlan, J.C. 2012. Intumescent all-polymer multilayer nanocoating capable of extinguishing flame on fabric. Advance Materials. 23(34):3926-3931.
Interpretive Summary: Layer-by-layer is a simple method to incorporate various polymers, colloids, or molecules into a thin film that is typically no thicker than 1µm. Poly (sodium phosphate), PSP, and poly (allylamine), PAAm, system was applied to cotton fabric in varying number of bilayer. After vertical flame test, the result is foamed char layers by the action of heat evolve gases on the surface of cotton fabric. This charred layer then acts as a physical barrier to the underlying material against heat and flame. This chemical system is called intumescence. This work demonstrates the first ever intumescent nanocoating prepared using layer-by-layer assembly. These all cotton coating provide an environmentally friendly alternative for protecting fabrics. The opportunity for further improvements is tremendous through the use of alternate polymers, nanoparticles, and small molecules that may enhance these effects.
Cotton fabric was treated with flame-retardant coatings composed of poly (sodium phosphate), PSP, which acts as the acid source, and poly (allylamine), PAAm, which is used as the blowing agent, prepared via layer-by-layer (LbL) assembly. By applying these thin coating on fabric, after-glow is eliminated and after-flame time is reduced in vertical flame test. Flame was completely extinguished on fabric coated with 20 BL of PSP/PAAm. In SEM study, especially on the 20 BL, bubbles were formed on the fiber surface during burning, which is believed due to an intumescent effect. From microscale calorimeter data, the peak heat release rate and total heat release of fabric show a 43% and 51% reduction compared to the control fabric, with only 1.7 wt% coating added. These results demonstrate that this coating provides a powerful flame retardant effect and yields durable char structures that cannot easily burn through.