Preparations, characterizations, thermal and flame retardant properties of cotton fabrics finished by boron-silica sol-gel coatings

This work aims to improve the thermal stability and flame retardancy of cotton fabrics by using sol-gel processes. A hybrid sol was prepared by using silica sol, coupling agent of gamma-Methacryloxypropyltrimethoxysilane (KH570) and flame retardant of sodium octaborate tetrahydrate (DOT) and then finished on the surface of cotton fabric. Fourier infrared spectroscopy (FTIR), X-ray electron spectroscopy (XPS), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), limiting oxygen index (LOI) and vertical burning test (VBT) were used to characterize the functional groups, surface element compositions, microscopic morphologies, thermal stability and flame retardancy of cotton fabrics, respectively. The results show that sols are successfully converted into gel coatings onto cotton fabrics. SiO2-KH570-DOT@Cotton shows the highest char residue rate (41.7%) and Delta LOI/Delta m (6.0%/g) values. SiO2, KH570 and DOT coatings have shown some competitive but more synergistic effects in flame retardancy. The three-dimensional structure of SiO2 gel can provide structural support, effectively block heat transfer and transports of oxygen. KH570 has a significant coupling effect of increasing interfacial compatibility between sols and cotton fabrics. DOT is thermally decomposed to generate boric acid to accelerate the carbonization degrees of cotton fibers and thus improve the thermal stabilities of char layers.

Automated summary

This study improves the thermal stability and flame retardancy of cotton fabrics using sol-gel processes. The sols are successfully converted into gel coatings on cotton fabrics, providing structural support and blocking heat and oxygen transfer. The combination of silica sol, coupling agent, and flame retardant in the coatings shows synergistic effects in flame retardancy.