Textination Newsline

In a new study, North Carolina State University researchers found they could separate blended cotton and polyester fabric using enzymes – nature’s tools for speeding chemical reactions. Ultimately, they hope their findings will lead to a more efficient way to recycle the fabric’s component materials, thereby reducing textile waste. However, they also found the process need more steps if the blended fabric was dyed or treated with chemicals that increase wrinkle resistance.

“We can separate all of the cotton out of a cotton-polyester blend, meaning now we have clean polyester that can be recycled,” said the study’s corresponding author Sonja Salmon, associate professor of textile engineering, chemistry and science at NC State. “In a landfill, the polyester is not going to degrade, and the cotton might take several months or more to break down. Using our method, we can separate the cotton from polyester in less than 48 hours.”
 
According to the U.S. Environmental Protection Agency, consumers throw approximately 11 million tons of textile waste into U.S. landfills each year. Researchers wanted to develop a method of separating the cotton from the polyester so each component material could be recycled.

In the study, researchers used a “cocktail” of enzymes in a mildly acidic solution to chop up cellulose in cotton. Cellulose is the material that gives structure to plants’ cell walls. The idea is to chop up the cellulose so it will “fall out” out of the blended woven structure, leaving some tiny cotton fiber fragments remaining, along with glucose. Glucose is the biodegradable byproduct of degraded cellulose. Then, their process involves washing away the glucose and filtering out the cotton fiber fragments, leaving clean polyester.
 
“This is a mild process – the treatment is slightly acidic, like using vinegar,” Salmon said. “We also ran it at 50 degrees Celsius, which is like the temperature of a hot washing machine.
“It’s quite promising that we can separate the polyester to a clean level,” Salmon added. “We still have some more work to do to characterize the polyester’s properties, but we think they will be very good because the conditions are so mild. We’re just adding enzymes that ignore the polyester.”

They compared degradation of 100% cotton fabric to degradation of cotton and polyester blends, and also tested fabric that was dyed with red and blue reactive dyes and treated with durable press chemicals. In order to break down the dyed materials, the researchers had to increase the amount of time and enzymes used. For fabrics treated with durable press chemicals, they had to use a chemical pre-treatment before adding the enzymes.

“The dye that you choose has a big impact on the potential degradation of the fabric,” said the study’s lead author Jeannie Egan, a graduate student at NC State. “Also, we found the biggest obstacle so far is the wrinkle-resistant finish. The chemistry behind that creates a significant block for the enzyme to access the cellulose. Without pre-treating it, we achieved less than 10% degradation, but after, with two enzyme doses, we were able to fully degrade it, which was a really exciting result.”

Researchers said the polyester could be recycled, while the slurry of cotton fragments could be valuable as an additive for paper or useful addition to composite materials. They’re also investigating whether the glucose could be used to make biofuels.

“The slurry is made of residual cotton fragments that resist a very powerful enzymatic degradation,” Salmon said. “It has potential value as a strengthening agent. For the glucose syrup, we’re collaborating on a project to see if we can feed it into an anaerobic digester to make biofuel. We’d be taking waste and turning it into bioenergy, which would be much better than throwing it into a landfill.”

The study, “Enzymatic textile fiber separation for sustainable waste processing,” was published in Resources, Environment and Sustainability. Co-authors included Siyan Wang, Jialong Shen, Oliver Baars and Geoffrey Moxley. Funding was provided by the Environmental Research and Education Foundation, Kaneka Corporation and the Department of Textile Engineering, Chemistry and Science at NC State.

Customized, biomedically applicable materials based on tropoelastin are being developed in a joint project by Skinomics GmbH from Halle, Martin Luther University Halle-Wittenberg and the Fraunhofer Institute for Microstructure of Materials and Systems IMWS. The material combines biocompatibility, durability, biodegradability and favorable mechanical properties similar to those of skin. Preclinical tests have confirmed that it is suitable for use as a wound dressing material used in the treatment of chronic and complex wounds.

Particularly in the context of an aging society, special wound dressings are gaining in importance. The treatment of complex wound diseases such as venous ulcers, leg ulcers, or foot ulcers is challenging for medical staff, long-term and painful for those affected and cost-intensive for the healthcare system. Innovative protein-based materials are now being used for the treatment of such wounds. However, since they are made from animal tissues, they carry increased risks of infection or can result in undesirable immune reactions. In addition, there are increasing reservations in the population about medical products of animal origin.

In the joint research project, the project partners are currently developing customized, biomedically applicable materials based on human tropoelastin. This precursor protein is converted in the body to elastin, a vital and long-lived structural biopolymer that has exceptional mechanical properties and thus gives the skin and other organs the elasticity and resilience they need to function.

“Elastin is chemically and enzymatically extremely stable, biocompatible and does not produce immunological rejections when used as a biomaterial in humans. Therefore, we want to create new and innovative solutions for the treatment of complex wounds based on human tropoelastin,” says Dr. Christian Schmelzer, Head of the Department of Biological and Macromolecular Materials at Fraunhofer IMWS.

Individual wound treatment
As part of the research project led by Prof. Dr. Markus Pietzsch of Martin Luther University Halle-Wittenberg, the researchers succeeded in developing a biotechnological process for modifying tropoelastin. The modified tropoelastin is processed at Fraunhofer IMWS. Here, an electrospinning procedure is used to produce ultra-thin nanofibers with diameters of only a few hundred nanometers. The resulting nonwovens are further crosslinked to stabilize them for the respective application. The procedures developed have been optimized so that biomedical parameters such as pore size, stability and mechanical properties are variable and can thus be customized to meet the requirements of the respective wound treatment. The materials produced using the new procedures are being investigated by Skinomics GmbH in initial preclinical tests with regard to their skin compatibility and have already achieved promising results.

At the end of the project by the end of this year, applications for intellectual property rights are to be filed, building the basis for a subsequent product development phase for certified medical products.