Textination Newsline

Reset
2 results
Photo: pixabay, Hilary Clark
01.02.2022

Cotton Fibers 2.0: Fireproof and comfortable

A new chemical process developed by Empa turns cotton into a fire-resistant fabric, that nevertheless retains the skin-friendly properties of cotton.

Conventional flame retardant cotton textiles suffer from release of formaldehyde and are uncomfortable to wear. Empa scientists managed to circumvent this problem by creating a physically and chemically independent network of flame retardants inside the fibers. This approach retains the inherently positive properties of cotton fibers, which account for three-quarters of the world's demand for natural fibers in clothing and home textiles. Cotton is skin-friendly because it can absorb considerable amounts of water and maintain a favorable microclimate on the skin.

A new chemical process developed by Empa turns cotton into a fire-resistant fabric, that nevertheless retains the skin-friendly properties of cotton.

Conventional flame retardant cotton textiles suffer from release of formaldehyde and are uncomfortable to wear. Empa scientists managed to circumvent this problem by creating a physically and chemically independent network of flame retardants inside the fibers. This approach retains the inherently positive properties of cotton fibers, which account for three-quarters of the world's demand for natural fibers in clothing and home textiles. Cotton is skin-friendly because it can absorb considerable amounts of water and maintain a favorable microclimate on the skin.

For firefighters and other emergency service personnel, protective clothing provides the most important barrier. For such purposes, cotton is mainly used as an inner textile layer that needs additional properties: For example, it must be fireproof or protect against biological contaminants. Nevertheless, it should not be hydrophobic, which would create an uncomfortable microclimate. These additional properties can be built into the cotton fibers by suitable chemical modifications.

Durability vs. toxicity
"Until now, it has always taken a compromise to make cotton fireproof," says Sabyasachi Gaan, a chemist and polymer expert who works at Empa's Advanced Fibers lab. 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. Currently, the textile industry has no other choice than to utilize formaldehyde-based chemicals – and formaldehyde is classified as a carcinogen. This has been an unsolved problem for decades. While formaldehyde-based flame retardant treatments are durable, they have additional drawbacks: The -OH groups of cellulose are chemically blocked, which considerably reduces the capability of cotton to absorb water, which results in an uncomfortable textile.

Gaan knows the chemistry of cotton fibers well and has spent many years at Empa developing flame retardants based on phosphorus chemistry that are already used in many industrial applications. Now he has succeeded in finding an elegant and easy way to anchor phosphorous in form of an independent network inside the cotton.

Independent network between cotton fibers
Gaan and his colleagues Rashid Nazir, Dambarudhar Parida and Joel Borgstädt utilized a tri-functional phosphorous compound (trivinylphosphine oxide), which has the capability of reacting only with specifically added molecules (nitrogen compounds like piperazin) to form its own network inside cotton. This makes the cotton permanently fire-resistant without blocking the favorable -OH groups. In addition, the physical phosphine oxide network also likes water. This flame retardant treatment does not include carcinogenic formaldehyde, which would endanger textile workers during textile manufacturing. The phosphine oxide networks, thus formed, does not wash out: After 50 launderings, 95 percent of the flame retardant network is still present in the fabric.

To render additional protective functionalities to the flame retardant cotton developed at Empa, the researchers also incorporated in situ generated silver nanoparticles inside the fabric. This works nicely in a one-step process together with generating the phosphine oxide networks. Silver nanoparticles provide the fiber with antimicrobial properties and survive 50 laundry cycles, too.

A high-tech solution from the pressure cooker
"We have used a simple approach to fix the phosphine oxide networks inside the cellulose," Gaan says. "For our lab experiments, we first treated the cotton with an aqueous solution of phosphorus and nitrogen compounds and then steamed it in a readily available pressure cooker to facilitate the crosslinking reaction of the phosphorus and the nitrogen molecules." The application process is compatible with equipment used in the textile industry. "Steaming textiles after dyeing, printing and finishing is a normal step in textile industry. So it doesn't require an additional investment to apply our process," states the Empa chemist.

Meanwhile, this newly developed phosphorus chemistry and its application is protected by a patent application. "Two important hurdles remain," Gaan says. "For future commercialization we need to find a suitable chemical manufacturer who can produce and supply trivinylphosphine oxide. In addition, trivinylphosphine oxide has to be REACH-registered in Europe."

Contact:
Dr. Sabyasachi Gaan
Advanced Fibers
Phone: +41 58 765 7611
sabyasachi.gaan@empa.ch
 
Contact:
Prof. Dr. Manfred Heuberger
Advanced Fibers
Phone: +41 58 765 7878
manfred.heuberger@empa.ch

A gel that releases drugs
The novel phosphorus chemistry can also be used to develop other materials, e.g. to make hydrogels that can release drugs upon changes in pH. Such gels could find application in treating wounds that heal slowly. In such wounds, the pH of the skin surface increases and the new phosphorus-based gels can be triggered to release medication or a dye that alerts doctors and nurses to the problem. Empa has also patented the production of such hydrogels.

Source:

EMPA, Rainer Klose

Protective masks for Augsburg University Hospital (c) Fraunhofer IGCV
14.04.2020

Protective equipment from 3d printers

  • Fraunhofer IGCV supplies protective equipment made via 3d printers to university hospital Augsburg

For more than a week, the Institute for Materials Resource Management at the University of Augsburg has been supplying the University Hospital Augsburg with protective masks from 3D printers. In order to meet the enormous demand for absolutely necessary protective equipment for the the needs of hospital staff, a call for support was sent to cooperation partners - Augsburg University of Applied Sciences and Fraunhofer IGCV are stepping in.
 

  • Fraunhofer IGCV supplies protective equipment made via 3d printers to university hospital Augsburg

For more than a week, the Institute for Materials Resource Management at the University of Augsburg has been supplying the University Hospital Augsburg with protective masks from 3D printers. In order to meet the enormous demand for absolutely necessary protective equipment for the the needs of hospital staff, a call for support was sent to cooperation partners - Augsburg University of Applied Sciences and Fraunhofer IGCV are stepping in.
 

Fast communication in the research network:
Production of 3D-printed parts accelerates in the shortest possible time
Without further ado, an internal university group searched for possibilities of manufacturing via 3D printing. Prof. Dr. Markus Sause and Prof. Dr. Kay Weidenmann of the Institute for Materials Resource Management at the University of Augsburg immediately agreed and pulled out all the stops to start production as quickly as possible. In order to provide as many protective masks as possible in the shortest possible time, an appeal was also made to existing cooperation partners. They found what they were looking for in their direct colleague Prof. Dr. Johannes Schilp, Professor of Production Informatics at the University of Augsburg and Head of the Processing Technology Department at the Augsburg Fraunhofer IGCV: Max Horn, research associate at the Fraunhofer Institute, and Paul Dolezal from the FabLab (production laboratory) at Augsburg University of Applied Sciences immediately promised their help. "Thanks to the excellent cooperation of our team, the first parts were produced in our laboratory for additive manufacturing just a few hours after the first telephone call," Max Horn recalls. "With the support of the Augsburg University of Applied Sciences and the Fraunhofer IGCV, the production capacity of 50 masks per day could be significantly increased," Markus Sause is pleased to report.
          

Printing masks with Fused Deposition Modeling (FDM)
Fused Deposition Modeling (FDM) was selected as the manufacturing process for the face protection. This means that the mask is created by forcing fusible plastic through a nozzle and applying it in layers in individual lanes. In addition to an extensive laboratory for metal-based additive manufacturing, the Fraunhofer IGCV operates a new laboratory unit with various FDM printers. Due to the simplicity of the process and its great flexibility, it is particularly suitable for prototypes and sample components. "However, the masks produced are by no means only illustrative objects", adds Georg Schlick, Head of the Components and Processes Department at the Fraunhofer IGCV. The team processed durable polymers for the parts, which have good resistance to the disinfectants used in the hospital. This results in high-quality components that are ideally suited for multiple use.
 
Additive manufacturing for flexible production
In the meantime, some bottlenecks have been overcome: The Institute for Materials Resource Management at the University of Augsburg is switching back to production processes for the manufacture of face masks that are better suited for the production of large quantities. "The great strength of additive manufacturing lies rather in the production of very complex components with smaller quantities," explains Matthias Schmitt, group leader for additive manufacturing at the Fraunhofer IGCV. "But 3D printing also enables us to act at very short notice and to compensate for lack of capacity for almost any component as required," Schmitt continues. Thanks to the flexibility, motivation and expertise of all cooperation partners, a complete production and supply chain for the face masks was implemented within a few days. Georg Schlick therefore emphasizes the need for good networking and rapid exchange between the research institutions. "The close networking within the 3D printing community enables short communication channels and fast action. This can save lives in this case."

Source:

Fraunhofer Institute for Casting, Composite and Processing Technology IGCV