Durable flame retardant finishing of cotton fabrics with halogen-free organophosphonate by UV photoinitiated thiol-ene click chemistry

Cotton fabrics are treated with a synthetic non-halogenated organophosphorus flame retardant by UV photoinitiated thiol-ene click chemistry. Thiol reactive precursors on cotton surface were prepared by 3-Mercaptopropyltriethoxysilane. The flame retardant property has been tested with different concentrations of flame retardant treatment (i.e., wt 2%, 5%, and 8%) by limited oxygen index (LOI) and vertical burning tests and maintained after 30 washing cycles, which was improved with concentration increases. Thermogravimetric analysis showed that the treatment greatly enhanced the char forming ability of cellulose and the highest residue was left as much as 48.1% char in nitrogen and 19.8% char in air after heating to 600 °C, which obviously more than those of untreated fabric. Scanning electronic microscopy (SEM) revealed that the weave structure and fiber shape in all treated fabrics were preserved. These results demonstrate that UV photoinitiated thiol-ene click chemistry is a facile method for imparting cotton fabric with durable flame-retardant properties.