Improved thermal stability and flame retardancy levels of cotton fabrics treated by GEL/AMP layer-by-layer assembly and silica gel composite coatings

Cotton fabrics were treated with Gelatin (GEL)/Adenosine 5 '-monophosphate (AMP) by layer-by-layer (LBL) assembly coatings and SiO2 sol-gel coatings to improve flame retardancy. Functional groups, surface element compositions, crystal structures, surface microscopic morphologies and element distributions of original and treated cotton fabrics were characterized by techniques including Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Scanning electron microscopy-Energy dispersive spectrometer (SEM-EDX). The results of FTIR, XPS, XRD and SEM-EDX show that the composite coatings are successfully deposited onto cotton fiber surfaces. Thermogravimetric, limiting oxygen index (LOI) experiments, vertical flammability tests (VFTs) and cone calorimetry tests (CCTs) were used to assess the thermal stabilities, flame retardancy levels and reaction-to-fire properties of cotton fabrics. The washing durability, air permeability and hydrophobicity levels were investigated by American Association of Textile Chemists and Colorists, Chinese national standard and water contact angle tests. Results show that the 10BL-SiO2@COT exhibits optimum flame retardancy level. Its char residue rate at 700.0 celcius increases by 506.7% when comparing with original cotton fabric. It has a LOI value of 30.3% (non-flammable level). It can self-extinguish with a char length of only 4.4 cm during a VFT. Its total heat release and peak heat release rate reduce by 18.7% and 50.4% when comparing with original cotton fabric. Its fire growth rate value decreases to 2.2 kW/(m(2)center dot s) with a synergistic effectiveness parameter of 1.3 (>= 1.0). In addition, its LOI value decreases by 26.1% after 10 laundering cycles, but its air permeability enhances by 5.8% as compared with original cotton fabric. Also, it is very hydrophilic. GEL/AMP LBL assembly and SiO2 gel coatings play more synergistic roles in providing physical barriers and structural supports, promoting and reinforcing char formations, cooling burning zones, diluting oxygen and gaseous products.

Automated summary

Cotton fabrics were treated with Gelatin/Adenosine 5'-monophosphate by layer-by-layer assembly coatings and SiO2 sol-gel coatings to improve flame retardancy. The treated fabrics showed successful deposition of the composite coatings and exhibited enhanced thermal stability, flame retardancy, and reaction-to-fire properties. The washing durability, air permeability, and hydrophobicity levels were also improved, making the treated fabrics suitable for various applications.