Modern flame retardant cotton textiles emit formaldehyde and are uncomfortably hot to the touch. Empa scientists solved the problem by embedding a physically and chemically separate network of flame retardants into the fibres. This method preserves cotton fibres’ intrinsic positive characteristics, which account for three-quarters of the world’s demand for natural fibres in apparel and household textiles. Cotton is skin-friendly because it can absorb a lot of water and keep a good microclimate on the skin.
For firefighters and other emergency service personnel, protective clothing provides the most important barrier. Wash-durable flame retardant cotton in industry is produced by treating the fabric with flame retardants, which chemically links to the cellulose in the cotton. Chemist Sabyasachi Gaan has succeeded in finding an elegant and easy way to anchor phosphorus in the form of an independent network inside the cotton fibers. This makes the cotton permanently fire-resistant without blocking the favorable -OH groups. After 50 laundering, 95 percent of the phosphine oxide network is still present in the fabric. In situ generated silver nanoparticles inside the cotton also render additional protective functionalities.
This works well in a one-step process alongside the generation of phosphine oxide networks. Silver nanoparticles give the fabric antibacterial characteristics and can withstand 50 laundry cycles.
The pressure cooker provides a high-tech answer.
“We used a straightforward approach to repair the phosphine oxide networks within the cellulose,” Gaan explains. “For our laboratory studies, we first treated the cotton with an aqueous solution of phosphorus and nitrogen compounds before steaming it in a pressure cooker to facilitate the crosslinking reaction of the phosphorus and nitrogen molecules.” The application technique is compatible with textile industry equipment. “In the textile industry, steaming fabrics after dyeing, printing, and finishing is a standard procedure. As a result, applying our procedure does not necessitate any further investment “According to the Empa chemist.
Meanwhile, this newly established phosphorus chemistry and its application is protected by a patent application. “Two significant obstacles remain,” Gaan explains. “We need to identify a suitable chemical company who can make and deliver trivinylphosphine oxide for future commercialization. Furthermore, trivinylphosphine oxide must be REACH-registered in Europe.”