Boost for hosiery and knitwear recycling

Category: GARMENTS

Country: Austria

By Haydn Davis
19th December 2023

Vienna: A method to overcome some the key issues surrounding the recycling of hosiery, clothing and textiles that contain elastane has been developed by researchers at the Vienna University of Technology (TU Wien) in Austria.

The team has been working on a process that as well as helping to detect the presence of elastane fibres, can also be used to separate it from other fibres that can then be more easily recycled.

In products such as women’s hosiery, for example, nylon fibre is often wrapped around an elastane core during yarn preparation prior to knitting, and as such is virtually impossible to separate back into the respective fibres for recycling.

Emanuel Boschmeier, part of the research team at the Institute of Chemical, Environmental and Bioscience engineering at TU Wien explained: "Many of the materials we use to manufacture clothing are easily recyclable as pure materials - such as cotton, polyester or polyamide.

"But elastane, even if it is only mixed in small quantities, makes recycling using conventional methods impossible. Elastane is so stretchy that the shredders that are usually used to shred textiles before recycling cannot cope with it. Elastane leads to soiling, blockages and clumping in the machines" -said Emanuel Boschmeier.

The first step involved developing a reliable and fast method to accurately detect elastane that differed from the traditional test method of using a solvent that is classified as harmful to health.

During the test, six different organic solvents were tested for their performance in dissolving elastane out of textile waste and were measured using the Hansen solubility parameters (HSPs). Experiments were conducted on polyester/elastane and polyamide/elastane blends with the non-hazardous solvent dimethyl sulfoxide (DMSO) determined to be the most effective.

The second step involved the lab-scale development of a process for the successful separation of elastane from textile waste, again based on a non-hazardous, environmentally friendly alternative solvent.

The team also provided evidence using spectroscopic and thermal methods that the process conditions caused no changes in the fully recovered polyester and polyamide.

"Complete recovery and simultaneous purification of the solvent used for elastane separation in a closed loop is possible," the team concluded. "We experimented with different solvents and carried out theoretical studies. We finally came across a harmless solvent that selectively removes the elastane, leaving the reusable fibres intact.

"Even when wool is combined with polyester and elastane, the individual components can be used.

"The wool is broken down with enzymes under mild, harmless conditions. This method produces an amino acid cocktail that can be used in the cosmetics industry or in fertilizer production. In the next step elastane is separated and recyclable polyester remains."

A patent application for the process has now been filed.

Courtesy: Knittingtradejournal.com