Today, only a fraction of all textiles are recycled. Katarina LindstrΓΆm wants to change that. Her doctoral thesis in Textile Technology at the Swedish School of Textiles contributed unique knowledge about mechanical recycling: which processes and materials give the best results.
In recent years, the need to address used textiles has become increasingly acute. With new legislation by the European Union, all textiles must be collected separately and in many municipalities, recycling centers have quickly become inundated.
At the same time, we see in the news another downside of overconsumption, where clothes and textiles are dumped abroad, far from the eyes of Swedish consumers.
These questions interested LindstrΓΆm, a textile engineer who studied at the Swedish School of Textiles, University of BorΓ₯s. When she started her doctoral studies a few years ago, she chose to focus on mechanical recycling.
“So far, very little about the subject has been described in the research. The industry does have knowledge on the topic, but these are trade secrets that it likes to keep to itself. If we are to achieve the goals of a more sustainable textile industry, we must become more open with this knowledge,” said LindstrΓΆm, who has written her thesis with the aim of making its content accessible to the industry.
Every millimeter counts
“Unlike chemical recycling, mechanical processes do not consume as much water or chemicals. Broadly speaking, the textile is cut and torn into smaller pieces in different stages. Sometimes water or lubricant is added to make it easier to separate the fibers from one another. This process is tough on the fibers, which are, of course, designed to hold the textile together,” explained LindstrΓΆm.
“If the fibers are too finely broken up during the process, it is not possible to spin them into new yarns. In this case, the material is downgraded to fill material or nonwoven fabric. In my tests, I have shown that there is a lot you can do to get longer, open fibers that could be used for yarns and textiles.”
In her work, she has carried out a large number of tests and developed new methods. Some of these methods test friction between fibers and some see how open a material is. In this context, “open” means that the fibers have been freed from the textiles.
Valuable results for the industry
In the comparison of two lab-scale recycling machines, woven and knitted constructions and yarns with different twists were examined. The aim was to see how the construction itself affects recyclability. The results showed that a looser textile with a lower twist yielded longer fibers. And the less mechanical processing, the better the quality of the fibers. To achieve this, lubricants were added.
“Lubricants reduce friction, and this proved to be particularly successful with polyester. With lubricants, less heat was required in the process, which is otherwise a challenge as it can lead to the polyester melting. I have also been able to show that the length of the fiber is affected by the direction in which the textile is fed into the machine,” said LindstrΓΆm.
She has also imitated how the use of a garment affects recyclability, i.e., how clothes are broken down by use and how it affects the length of the fiber. Together with Master’s students from Saxion University of Applied Science in the Netherlands, she has investigated how the right kind of pre-treatment can provide longer fibers and improve spinnability.
Many textiles today are made of mixed materials. They are more difficult yet not impossible to recycle, said LindstrΓΆm, who hopes that her results can be helpful when clothing recycling increases. It is a very important piece of the puzzle for a more sustainable world. But recycling can never be the only solution.
“The best thing is that we use our clothes more, repair our garments when needed, and re-design them when they go out of style. In this way, as little energy as possible is used,” said LindstrΓΆm.
Provided by
University of BorΓ₯s
