State-of-the-art flame-retardant cotton fabrics suffer from formaldehyde emissions and are uncomfortable to wear. Empa scientists have succeeded in avoiding this problem by creating physically and chemically independent networks of flame retardants within the fiber. This approach retains the inherently positive properties of cotton fibers, accounting for three-quarters of the world’s demand for natural fibers in clothing and household fibers. Cotton is gentle on the skin as it absorbs a significant amount of water and can maintain a favorable microclimate for the skin.
For firefighters and other paramedics Protective clothing It provides the most important barrier. For that purpose, cotton Mainly used as an inner fiber Layers that require additional properties: For example, they must be fire resistant or protected from biological contaminants. Nevertheless, it should not be hydrophobic, which would create an unpleasant microclimate. These additional properties can be incorporated into cotton fibers with appropriate chemical modifications.
Durability and toxicity
“In the past, there has always been a compromise to make cotton fire resistant,” says Sabyasachi Gaan, a chemist and polymer expert at Empa’s Advanced Fibers lab. Industrial wash-durable flame-retardant cotton is produced by treating the fabric with a flame retardant that chemically binds to the cellulose in the cotton. Currently, the textile industry has no choice but to use formaldehyde-based chemicals, and formaldehyde is classified as a carcinogen. This has been an open issue for decades. Formaldehyde-based flame retardant treatment is durable, but has additional drawbacks. The chemical blocking of the -OH groups of cellulose significantly reduces the ability of cotton to absorb water, making the fibers uncomfortable.
Ghan is familiar with the chemistry of cotton fibers and has spent many years developing flame retardants based on the chemistry of phosphorus, which is already used by many. Industrial application.. Now he has succeeded in finding an elegant and easy way to secure phosphorus in the form of an independent network in cotton.
Independent network between cotton fibers
Gaan and his colleagues Rashid Nazir, Dambarudhar Parida, and Joel Borgstädt are trifunctional phosphorus compounds that have the ability to react only with specially added molecules (nitrogen compounds such as piperazine) to form a unique network inside the cotton. (Trivinylphosphine oxide) was used. This makes the cotton permanently fire resistant without blocking the preferred -OH groups. In addition, the physical phosphine oxide network also likes water. This flame retardant treatment does not contain carcinogenic formaldehyde, which puts textile workers at risk during textile production. The phosphine oxide network thus formed is not washed away: 95% of the flame retardant after 50 washes Communication network It still exists in the fabric.
To render additional protection to flame Delay agent The cotton developed at Empa incorporates in-situ generated silver nanoparticles into the fabric. This works well in a one-step process, along with the formation of a phosphine oxide network. The silver nanoparticles provide antibacterial properties to the fibers and can withstand 50 washing cycles.
High-tech solution for pressure cooker
“We used a simple approach to fix the phosphine oxide network inside the cellulose,” says Gaan. “In our laboratory experiments, cotton was first treated with an aqueous solution of phosphorus and nitrogen compounds and then steamed in a ready-to-use pressure cooker to accelerate the cross-linking reaction between phosphorus and nitrogen molecules.” The application process is compatible with the equipment used in the textile industry. “Steaming textiles after dyeing, printing and finishing is a normal step in the textile industry, so no additional investment is required to apply our process,” says Empa’s chemist.
Meanwhile, this newly developed phosphorus chemistry and its applications are protected by patent applications. “There are two important hurdles left,” says Gaan. “For future commercialization, we need to find a suitable chemical manufacturer capable of producing and supplying trivinyl phosphine oxides. In addition, trivinyl phosphine oxides must be REACH registered in Europe.”
Rashid Nazir et al, In-situ Phosphine Oxide Physical Network: A Simple Strategy for Achieving Durable Flame Retardant and Antibacterial Treatment of Cellulose, Chemical Engineering Journal (2020). DOI: 10.1016 / j.cej.2020.128028
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Make cotton that is fire resistant and comfortable
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