One-pot fabrication of bio-based hydrophobic and flame-retardant coating for cotton fabric

The facile fabrication of eco-friendly flame-retardant coatings with high efficiency, hydrophilicity, and good softness for cotton fabrics is imperative, but still challenging. Here, we construct an environmentally friendly hydrophobic and fire-safety coating on cotton fabric through a one-pot sol-gel method based on biobased phytic acid (PA), tannic acid (TA), and vinyl trimethoxysilane (VTS). In this system, PA as an acid source, TA as a charring agent, together with VTS as a silicon source construct a phosphorus/nitrogen/silicon-containing high-efficiency hybrid flame-retardant system. Under an ultralow loading of 9.5 wt%, the coating can enable cotton fabric with self-extinguishing behavior during vertical burning test, a high limiting oxygen index of 29%, significantly reduced heat release (~ 68.9%), and almost negligible smoke release (down to 0). Additionally, TA can react with PA and VTS to largely reduce the hydrophilic groups during the sol-gel process, while the presence of hydrophobic vinyl functional groups further turns the hydrophilic surface of cotton fabric to a hydrophobic surface with a water contact angle of 117.2°. In addition, the physical properties of the resultant cotton fabrics are almost unchanged. This work offers new perspective for facile fabricating hydrophobic coatings with the merits of satisfactory flame retardancy, environmental friendliness, along with softness.