Dithiophosphate-and alkoxysilyl-functionalized polysiloxane as a durable flame-retardant and hydrophobic modifier for cotton fabrics

In this study, a novel functionalized polysiloxane containing dithiophosphate and alkoxysilyl groups was synthesized and applied as a dual flame-retardant and hydrophobic modifier for cotton fabrics. Poly(methylvinyl)siloxane was obtained via ring-opening polymerization of cyclosiloxane, followed by sequential thiol-ene functionalization. The structure of the synthesized polysiloxane was characterized using Fourier-transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy. Cotton fabrics were modified using a simple one-step dip-coating process. The presence of the modifier on the fiber surface was confirmed by FT-IR, scanning electron microscopy with energy-dispersive spectroscopy (SEM–EDS), and scanning electron microscopy (SEM). The modified fabrics exhibited enhanced flame-retardant properties, evidenced by a significant reduction in heat release rate (HRR) and a shift in the HRR peak to lower temperatures. The best performance was observed in fabrics treated with a 10% solution, which achieved a 55% reduction in HRR peak. The water contact angle (WCA) of the most effective samples reached 140°, indicating strong hydrophobicity. Thermogravimetric analysis (TG/DTG) revealed altered decomposition pathways, with the modified fabrics forming a stable char layer.