Clay Layers Help Fabrics Fight Flames

A flame-retardant coating has been developed by using layer-by-layer assembly to apply branched polyethylenimine and sodium montmorillonite clay to cotton fabric (ACS Nano, DOI: 10.1021/nn100467e). The method offers a relatively simple way to impart flame-resistance to clothing and other materials, the coating’s inventors say. Polymers mixed with montmorillonite clay have previously been shown to form a protective charred ceramic surface layer on materials when exposed to high heat. In the first in-depth study of a layer-by-layer assembled flame retardant, a team led by Jaime C. Grunlan of Texas A&M University, College Station, used the technique to apply polyethylenimine-montmorillonite nanocomposites to cotton fabric. In flame tests, fabrics treated with the nanocomposites left behind a significant residue after burning, whereas untreated fabrics underwent complex combustion. Microscopic analysis of the treated material showed that the fabric’s weave was well preserved after exposure to a flame and each individual yarn had developed the protective coating. The researchers note that, unlike some flame retardants, there is little difference in the appearance and feel of the treated and untreated fabric before burning.