Construction of a β-cyclodextrin-based colloid containing silicon, phosphorus and nitrogen components: Toward enhancing flame retardancy of flax fabrics

Natural cellulose fabrics, as one of the combustibles prone to causing indoor fires, are modified with flame retardants encouraged by the fire protection industry. Herein, a bio-based colloid named ASDPC was prepared by 3-aminopropyltriethoxysilane, diethylenetriaminepentakis(methylphosphonic acid) and β-cyclodextrin, and used to enhance the flame retardancy of flax fabrics via the pad-dry-cure method. The treated flax fabrics named ASDPC-FF showed good flame retardancy with a damaged length of only 6.4 cm in the vertical burning test and a limiting oxygen index value of up to 33.8 %. Meanwhile, ASDPC-FF exhibited thermal stability and combustion behavior distinct from untreated flax fabrics. Thermogravimetric analysis presented that the char residue produced by ASDPC-FF at 800 °C was as high as 36.2 %. Cone calorimetry test indicated that the peak heat release rate and total heat release of ASDPC-FF decreased by approximately 89.0 % and 35.7 %, respectively. Furthermore, compared to untreated flax fabrics, condensed-phase and gas-phase studies found that ASDPC-FF turned into expanded char and produced fewer gaseous volatiles containing C-H, C O and C-O-C at high temperatures. More importantly, ASDPC-FF remained self-extinguishing after 25 laundering cycles with flame retardancy surpassing untreated flax fabrics. In summary, this work provides a novel route for expanding the manufacture of flame-retardant flax fabrics.