Highly efficient flame retardation of polyester fabrics via novel DOPO-modified sol-gel coatings

Polyester fabrics are widely used in clothing and home furnishings, but they are highly flammable and often suffer from serious melt dripping problems. Sol-gel coatings have been employed to give the fabric flame retardancy, but these coatings are often unsatisfactory in the efficiency. To improve the flame retardancy of polyester fabrics in an eco-friendly and facile way, a 9, 10- dihydro-9, 10-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-modified colloidal silica (called PAPS-DOPA) was developed by the neutralization of poly(γ-aminopropyl silsesquioxane) (PAPS) and dibenzo[c,e][1,2] oxaphosphinic acid (DOPA). PAPS-DOPA is a colorless, highly transparent, and conformal coating that can be deposited on the surface of polyester fabrics via a sol-gel technique. With an ultra-low loading (even 1 wt.%), PAPS-DOPA can completely stop melt-dripping and efficiently reduce the flammability of polyester fabrics without deteriorating their thermal stability. With an 8 wt.% add-on of PAPS-DOPA coatings, the fabrics had a limiting oxygen index (LOI) value as high as 32% (LOI = 21.5% for the untreated fabrics) and showed a significant delay of ignition and a decrease in the heat release rate relative to the reference samples in the cone calorimetry test. PAPS-DOPA showed a dominating vapor-phase flame-retardant activity due to the presence of the DOPO component.