Highly transparent and environment-friendly flame-retardant coating for cotton and silk fabrics

Natural textiles are ubiquitous and irreplaceable in daily life but suffer from their inherent flammability, which poses a substantial threat to property and life safety in the event of fire. Flame-retardant protective coatings are widely regarded as an efficacious means to address this problem. However, most conventional flame-retardant coatings often appear opaque or dark in color. Herein, we report a transparent and environment-friendly flame-retardant coating via a facile one-pot sol-gel strategy derived from diphenylphosphinic acid (DPPA) and 3-aminopropyltriethoxysilane (APTES). In this system, the homogeneous three-dimensional cross-linked polysiloxane-based network leads to a high light transmittance of 98 % in the visible region. Meanwhile, the resultant coating exhibits robust interfacial adhesion and great applicability to fabric substrates. Remarkably, the synergistic effect between phosphorus (P), nitrogen (N) and silicon (Si) endows the coating with a clearly visible char-forming capacity, which further imparts excellent flame retardancy to both cotton and silk fabrics, featuring a desired LOI value, self-extinguish behavior and low heat release. This work provides a fresh perspective on the design of universal flame-retardant coating, particularly integrating the virtues of environment friendliness, transparency, and colorlessness.