Flame Retardancy and Mechanism of Cotton Fabric Finished by Phosphorus Containing SiO2 Hybrid Sol

Sol-gel method was used by taking tetraethyl orthosilicate (TEOS) as precursor, ethanol (C
₂
H
₅
OH) as solvent and hydrochloric acid (HCl) as catalyst, 1-γ-methacryloxypropyl trimethoxysilane (KH570) as a coupling agent for preparations of SiO
₂
, KH570 and 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO, flame retardant) sols to improve flame retardancy and thermal stability of cotton fabrics. Dipping-baking process was used for finishing cotton fabrics. Surface morphology, surface functional group and element distribution, intrinsic crystal structure, pyrolysis characteristics and flame retardancy of cotton fabrics were characterized by Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TG), and limiting oxygen index (LOI). Results show that DOPO and SiO
₂
sol have good synergistic flame retardant effect. Cotton fabric finished by hybrid sol of SiO
₂
-KH570-DOPO has the best flame retardant effect, its LOI is 22.8 %, ΔLOI/Δm is 4.20 %/g. DOPO-contained hybrid sol can promote formation of three-dimensional microscopic gel coating and residual char in condensed phase.