Finishing of cotton fabrics by multi-layered coatings to improve their flame retardancy and water repellency

In this study, we finished cotton fabrics with polyethylenimine (PEI)/melamine and phytic acid (PA) by layer-by-layer assembly to enhance their flame retardant properties. Subsequently, the flame retardant treated cotton fabrics were impregnated with a diluted solution of poly(dimethylsiloxane) (PDMS) for improving water repellent behavior. The morphology and chemical composition of un-treated and treated cotton fabrics were measured by scanning electron microscopy equipped with Energy Dispersive X-ray analysis. Thermogravimetric analysis indicated that the addition of melamine/PEI–PA coating induced earlier degradation of cotton fabrics to form char, and the presence of PDMS further improved the char yield. The flame retardant property was significantly enhanced as evidenced by the self-extinguishing behavior of Cotton-4BL and Cotton-4BL-PDMS fabrics in the vertical burning tests. The peak heat release rates of the treated cotton fabrics were decreased by more than 50% in contrast to that of the original cotton. The significant improvement in flame retardancy was attributed to the catalytic effect of the melamine/PEI–PA coating on char formation and the char stabilization effect of PDMS. The char layer with good thermal resistance played a crucial role in suppressing flame spread. The Cotton-4BL-PDMS fabrics also exhibited good water repellent behavior, which displayed an initial contact angle larger than 130° and almost unchanged over time.