Textination Newsline

High dependence on fossil carbon, associated high carbon footprint, low recycling rates and microplastics: several solutions are emerging.

The evolution of the demand for textile fibres from 1960 to the present day shows how the textile industry found itself in this dilemma. In 1960, around 95% of textile fibres were of natural origin, from bio-based carbon, and there was no problem with microplastics, all fibres were biodegradable.

The explosion in demand – 650% between 1960 and 2023 – could only be met by synthetic fibres from the chemical and plastics industries. Their share grew from 3% in 1960 to 68% in 2023 and from less than 700,000 tonnes to 85 million tonnes/year (The Fiber Year 2024). The new fibres covered a wide range of properties, could even achieve previously unknown properties and, above all, thanks to a powerful and innovative chemical and plastics industry, production volumes could be rapidly increased and comparatively low prices realised.
 
At the same time, sustainability has declined, the carbon footprint of the textiles has increased significantly and the issue of microplastics requires solutions.

The first step would be to significantly increase the proportion of renewable fibres, as this is the only way to reduce dependence on fossil carbon, especially in the form of crude oil, and thus reduce the carbon footprint. But how can this be done? As defined by the Renewable Carbon Initiative, renewable carbon comes from biomass, CO₂ and recycling: From carbon above ground. This addresses the core problem of climate change, which is extracting and using additional fossil carbon from the ground that will end up in the atmosphere.
 
What can cotton, bast fibres and wool contribute?
Cotton fibre production can hardly be increased, it is stagnating between 20 and max. 25 million tonnes/year. Cultivated areas can hardly be expanded, and existing areas are salinized by the irrigation required. With the exception of about 1% organic cotton, significant amounts of pesticides are used. The market share of “preferred” cotton – defined by a list of recognized programmes – will fall from 27% of total cotton production in 2019/20 to 24% in 2020/21, after years of growth. (Textile Exchange, October 2022: Preferred Fiber & Materials Market Report) Bast fibres such as jute (75%), flax, hemp, ramie or kenaf would require a huge boost in technology development and capacity investment and will nevertheless probably remain more expensive than cotton, simply because bast fibres are much more complicated to process, e.g. separating the fibre from the stalk, which is not necessary for cotton as a fruit fibre. As a source of cellulose fibre, bast fibres will remain more expensive than wood.

Although bast fibres are more sustainable than many other fibres, there is unlikely to be a major change – unless China focuses on bast fibres as a substitute for cotton. Plans to do so have been put on hold due to technological problems.

The importance of man-made cellulosic fibres (MMCFs) or simply cellulose fibres
Cellulose fibre production has been growing steadily over the last decades, reaching an all-time high of nearly 8 million tonnes in 2023, and is expected to grow further to 11 million tonnes in 2030. Cellulosic fibres are the only bio-based and biodegradable fibres that cover a wider range of properties and applications and can rapidly increase their capacity. The raw materials can be virgin wood as well as all types of cellulosic waste streams from forestry, agriculture, cotton processing waste, textile waste and paper waste. Increasing the share of cellulosic fibres will therefore play a crucial role in solving the sustainability challenges of the textile industry.

The production of MMCFs includes viscose, lyocell, modal, acetate and cupro. The market share of FSC and/or PEFC certified MMCF increased from 55–60% in 2020 to 60–65% of all MMCF in 2021. The market share of “recycled MMCFs” increased to an estimated share of 0.5%. Much research and development is underway. As a result, the volumes of recycled MMCFs are expected to increase significantly in the coming years. (Textile Exchange, October 2022: Preferred Fiber & Materials Market Report)

The CEPI study “Forest-Based Biorefineries: Innovative Bio-Based Products for a Clean Transition” (renewable-carbon.eu/publications/product/innovative-bio-based-products-for-a-clean-transition-pdf/) identified 143 biorefineries in Europe, of which 126 are operational and 17 are planned. Most of them are based on chemical pulping (67%) – the precursor of cellulose fibres. Most biorefineries are located in Sweden, Finland, Germany, Portugal and Austria. But there are already biorefineries in operation or planned in 18 different European countries.

The global report “Is there enough biomass to defossilise the Chemicals and Derived Materials Sector by 2050?” (upcoming publication end of February 2025, available here: renewablecarbon.eu/publications) shows particularly high growth in dissolving/chemical pulp (from 9 in 2020 to 44 million tonnes in 2050; growth of 406%), cellulose fibres (from 7 in 2020 to 38 million tonnes in 2050; growth of 447%) and cellulose derivatives (from 2 in 2020 to 6 million tonnes in 2050; growth of 190%).

Biosynthetics – Bio-based and CO₂-based Synthetic Fibres
To further reduce the share of fossil-based synthetic fibres, bio-based polymer fibres (also called “biosynthetics”) are an excellent option because of their wide range of properties – only the implementation will take decades as the share today is only below 0.5%. There are many options, such as polyester fibres (PLA, PTT, PEF, PHA), polyolefin fibres (PE/PP), bio-based PA fibres from castor oil. PTT, for example, is well established in the US carpet market and PLA in the hygiene market. They are all bio-based, but only a few are also biodegradable (PLA, PHA).
 
Biosynthetics are one of many applications of bio-based polymers. In general, 17 bio-based polymers are currently commercially available with an installed capacity of over 4 million tonnes in 2023. Ten of these bio-based polymers are used as biosynthetics. resulting in the production of over one million tonnes of biosynthetics (nova report: Bio-based Building Blocks and Polymers – Global Capacities, Production and Trends 2023–2028, renewable-carbon.eu/publications/product/bio-based-buildingblocks-and-polymers-global-capacities-production-and-trends-2023-2028-short-version/).

In principle, many fibres can also be made from CO₂, but here the technology and capacity needs to be developed, perhaps in parallel with the production of sustainable aviation fuels from CO₂, which will become mandatory.

Circular Economy – Recycling of Textile Waste & Fibre-to-Fibre Recycling
The textile industry is at a pivotal moment, where sustainability is no longer an option but a necessity. As the environmental impact of textile production and disposal becomes increasingly clear, the pressure to adopt circular economy principles is growing.

One promising solution is fibre-to-fibre recycling, a process that converts used textiles into new, highquality fibres, effectively closing the waste loop. While significant progress has been made in the European Union, challenges remain, particularly in scaling up technologies, lack of collection systems and handling of mixed fibre textiles. Europe currently generates approximately 6.95 (1.25 + 5.7) million tonnes of textile waste per year, of which only 1.95 million tonnes is collected separately and 1.02 million tonnes is treated by recycling or backfilling.
 
The recycling of textiles reduces the demand for virgin fibres and the textile footprint. The share of recycled fibres increased slightly from 8.4% in 2020 to 8.9% in 2021, mainly due to an increase in bottlebased PET fibres. However, in 2021, less than 1% of the global fibre market will come from pre- and post-consumer recycled textiles (Textile Exchange, October 2022: Preferred Fiber & Materials Market Report). New regulations from Brussels for closed-loop recycling, especially bottle-to-bottle recycling, could threaten the use of bottle-based PET fibres in the textile industry. This would mean a reduction in recycling rates in the textile industry until the logistics and technologies are in place to recycle textiles on a large scale. This will be necessary to contribute to the circular economy. Several research projects are underway to find solutions and first pilot implementations are available.

The Future of Sustainable Textiles
The sustainable textile industry of the future will be built on a foundation of cotton fibres and fast-growing cellulose fibres, later strongly supported by bio- and CO₂-based synthetic fibres (“biosynthetics”), and high recycling rates for all types of fibres. This combination can eventually replace most fossil-based synthetic fibres by 2050.

To get the latest information on cellulose fibres, the nova-Institute organises the “Cellulose Fibres Conference” every year, which will take place next time in Cologne on 12 and 13 March 2025 – this year for the first time with biosynthetics.

In collaboration with industrial partners, researchers at the Fraunhofer WKI have developed a vehicle underbody made from natural fibers and recycled plastics for automotive construction. The focus at the Fraunhofer WKI was directed at the development of the materials for injection molding as well as the hydrophobization of flax and hemp fibers for natural-fiber-reinforced mixed-fiber non-wovens.

The component fulfills the stringent technical requirements in the underbody area and could replace conventional lightweight vehicle underbodies in the future. With this development, the climate and environmental balance is optimized throughout the entire product life cycle.

The project partners Fraunhofer WKI, Thuringian Institute for Textile and Plastics Research (TITK), Röchling Automotive SE & Co. KG, BBP Kunststoffwerk Marbach Baier GmbH and Audi AG have succeeded in developing a sustainable overall concept for vehicle underbodies. The researchers have thereby taken a challenging component group with a high plastic content and made it accessible for the utilization of natural materials. Until now, natural-fiber-reinforced plastics have predominantly been used in cars for trim parts without significant mechanical functions. Structural components such as vehicle underbodies are, however, exposed to enormous loads and place high demands on the bending and crash behavior of the material. In modern lightweight vehicle concepts, high-performance materials made from glass-fiber-reinforced plastics are therefore utilized.

The project team was able to replace the glass fibers with natural materials such as flax, hemp and cellulose fibers and to produce underbody components with a natural-fiber content of up to 45%. In the area of polymers, virgin polypropylene was completely dispensed with and solely recyclates were utilized. All the challenges associated with this material changeover – both the lower initial mechanical properties of the materials and the temporally restricted processing windows – were solved by means of skillful compound combinations.

At the Fraunhofer WKI, materials for injection molding were developed. “Natural-fiber injection-molded compounds have so far been known primarily for their increased strength and stiffness compared to non-reinforced polymers. In the development of the vehicle underbody, we have furthermore succeeded in fulfilling the stringent requirements for low-temperature impact strength through an innovative combination of selected post-consumer recyclates (PCR) as a matrix and natural fibers of varying degrees of purity - without forfeiting the required stiffness and strength,” explained Moritz Micke-Camuz, Project Manager at the Fraunhofer WKI.

Within the framework of the development, fiber-composite components made from natural-fiber-reinforced mixed-fiber non-wovens (lightweight-reinforced thermoplastic, LWRT) were realized for the first time at the TITK and at Röchling. The developed product not only fulfills the mechanical requirements: It also withstands in particular the challenges posed by the humid environment in which it is used. For the hydrophobization of flax and hemp fibers for LWRT components, a continuous furfurylation process was developed at the Fraunhofer WKI. Through furfurylation, moisture absorption can be reduced by up to 35 percent without impairment of the bending strength of the subsequent components. The furfurylated fiber material can also be easily processed on a non-woven production line.

The prototype components produced were subsequently extensively tested both at component level and in road tests. Amongst others, the vehicles from the VW Group’s new “Premium Platform Electric” (PPE) were used for this purpose. Long-term experience has already been gathered within the framework of the series testing. The gratifying result of these tests: The newly developed biocomposites fulfill all standard requirements for underbody components and have proven to be suitable for series production. Neither the use of natural fibers nor of (post-consumer) recyclates leads to a significant impairment of the properties.

One major advantage of the innovation is the significantly improved carbon footprint: Compared to series production, 10.5 kilograms of virgin material (PP/glass fiber) can be replaced by 4.2 kilograms of natural fibers and 6.3 kilograms of post-consumer recyclate. As a result, CO2 emissions during production, use and product life have been reduced by up to 40 percent.

Within the scope of the development project, an innovative, holistic overall concept for vehicle underbodies, including recycling with cascading re-use of the components, was developed. From a technical point of view, vehicle underbodies can be manufactured entirely from the new, high-performance lightweight bio construction material in the future.

The project was funded by the German Federal Ministry for Economic Affairs and Climate Action (BMWK) via the project management organization TÜV Rheinland.

By reinforcing concrete with textiles instead of steel, it is possible to use less material and create slender, lightweight structures with a significantly lower environmental impact. The technology to utilise carbon fibre textiles already exists, but it has been challenging, among other things, to produce a basis for reliable calculations for complex and vaulted structures. Researchers from Chalmers University of Technology, in Sweden, are now presenting a method that makes it easier to scale up analyses and thus facilitate the construction of more environmentally friendly bridges, tunnels and buildings.

"A great deal of the concrete we use today has the function to act as a protective layer to prevent the steel reinforcement from corroding. If we can use textile reinforcement instead, we can reduce cement consumption and also use less concrete − and thus reduce the climate impact," says Karin Lundgren, who is Professor in Concrete Structures at the Department of Architecture and Civil Engineering at Chalmers.

Cement is a binder in concrete and its production from limestone has a large impact on the climate. One of the problems is that large amounts of carbon dioxide that have been sequestered in the limestone are released during production. Every year, about 4.5 billion tonnes of cement are produced in the world and the cement industry accounts for about 8 percent of global carbon dioxide emissions. Intensive work is therefore underway to find alternative methods and materials for concrete structures.

Reduced carbon footprint with thinner constructions and alternative binders
By using alternative binders instead of cement, such as clay or volcanic ash, it is possible to further reduce carbon dioxide emissions. But so far, it is unclear how well such new binders can protect steel reinforcement in the long term.

"You could get away from the issue of corrosion protection, by using carbon-fibres as reinforcement material instead of steel, because it doesn't need to be protected in the same way. You can also gain even more by optimising thin shell structures with a lower climate impact," says Karin Lundgren.

In a recently published study in the journal Construction and Building Materials, Karin Lundgren and her colleagues describe a new modelling technique that was proved to be reliable in analyses describing how textile reinforcement interacts with concrete.

"What we have done is to develop a method that facilitates the calculation work of complex structures and reduces the need for testing of the load-bearing capacity," says Karin Lundgren.

One area where textile reinforcement technology could significantly reduce the environmental impact is in the construction of arched floors. Since the majority of a building’s climate impact during production comes from the floor structures, it is an effective way to build more sustainably. A previous research study from the University of Cambridge shows that textile reinforcement can reduce carbon dioxide emissions by up to 65 percent compared to traditional solid floors.

Method that facilitates calculations
A textile reinforcement mesh consists of yarns, where each yarn consists of thousands of thin filaments (long continuous fibres). The reinforcement mesh is cast into concrete, and when the textile-reinforced concrete is loaded, the filaments slip both against the concrete and against each other inside the yarn. A textile yarn in concrete does not behave as a unit, which is important when you want to understand the composite material's ability to carry loads. The modelling technique developed by the Chalmers researchers describes these effects.

"You could describe it as the yarn consisting of an inner and an outer core, which is affected to varying degrees when the concrete is loaded. We developed a test and calculation method that describes this interaction. In experiments, we were able to show that our way of calculating is reliable enough even for complex structures," says Karin Lundgren.

The work together with colleagues is now continuing to develop optimisation methods for larger structures.

"Given that the United Nations Environment Programme (UNEP) expects the total floor area in the world to double over the next 40 years due to increased prosperity and population growth, we must do everything we can to build as resource-efficiently as possible to meet the climate challenge," says Karin Lundgren.

Just in time for summer: The Swiss start-up Swijin is launching a new sportswear category with its SwimRunner – a sports bra together with matching bottoms that works as both swimwear and running gear and dries in no time. The innovative product was developed together with Empa researchers in an Innosuisse project. The SwimRunner can be tested this weekend at the Zurich City Triathlon.
 
A quick dip after jogging without having to change clothes? Swijin (pronounced Swie-Djin), a new Swiss TechTex start-up, is launching its first product, the SwimRunner: a sports bra and bottoms that function as both swimwear and running gear and dry in a flash.

For the first time, this innovation enables women to make a smooth transition between land and water sports without having to change clothes. For example, hikers and runners can easily go into the water to cool off. Stand-up paddlers wearing the SwimRunner enjoy unrestricted freedom of movement and at the same time sufficient support, both on the board and in the water.
Science to boost sports performance
 
What appears to be a relatively simple requirement at first glance has turned out to be an extremely complex product to develop. As part of an Innosuisse project, Swijin collaborated with the Empa Biomimetic Membranes and Textiles laboratory in St. Gallen. Led by Empa engineer Martin Camenzind, the researchers first defined the requirements for the material and cut of the sports bra. "During development, we faced three main challenges: On the one hand, the product had to meet the requirements of a heavy-duty sports bra on land. At the same time, it had to maintain the compression of a swimsuit in the water – and do so with a very short drying time," says Camenzind.

Since no comparable garment exists on the market yet, the team also developed new tests for evaluating the high-performance textile. "Moreover, we designed a mannequin: a model of the female torso that can be used to measure the mechanical properties of bras," explains the researcher. In addition to scientific findings, the product development process also incorporated a great deal of expertise from sports physiologists, textile engineers, industry specialists, designers and, of course, female athletes.

Highest demands
Many of these athletes come from the swimrun scene. Swimrun is a fast-growing adventure sport that originated in the skerry gardens of Sweden. Unlike triathletes, who start out by swimming, then bike, and finally run, swimrunners switch back and forth between trail running and open water swimming throughout the race. The intensity of this sport provided Swijin with the optimal conditions for product development – and gave its name to the first collection, SwimRunner. "The feedback from female athletes was one of the deciding factors for the success of the product. They often swim and run for six to seven hours at a stretch. When they were satisfied with our prototypes, we knew: The SwimRunner is ready for market," says Swijin founder Claudia Glass.

The product idea first came to Claudia Glass while she was on vacation on Mallorca. During her morning runs, she longed to be able to take a quick dip in the sea. "Sports bras, however, are not designed for swimming," the founder explains. "They soak up the water and never seem to dry because of their thick compression material. Last summer, I wore the SwimRunner prototype all day. In the morning, I ran to Lake Zurich with my dog and jumped in. When I got back home, I could have just sat down at my desk and started working – I was completely dry and felt very comfortable."

Design and sustainability
The young company makes a point of combining engineering and design. Swijin's creative director, Valeria Cereda, is based in the center of the world's fashion capital, Milan, and infuses her experience with luxury brands into Swijin's aesthetic. But as a former competitive swimmer, she is also focused on functionality.

Swijin's high-performance products can only be realized with synthetic materials. The young company is determined to reduce the environmental impact of its products to a minimum. The tight supply chain keeps the CO₂ footprint low. The materials of the SwimRunner are 100% made in the EU and designed for quality.

Traditional garment labels only provide information about where the garment was made. Swijin is working with supplier Avery Dennison to provide all products with a Digital Identity Label. This gives consumers detailed information about the entire value chain, right down to the textile manufacturer's investment in reducing its carbon footprint and the use of the water-based, solvent-free logo. Swijin packages all materials in Cradle-to-Cradle Gold certified packaging, which is produced by Voegeli AG in Emmental.

Furthermore, Swijin proactively addresses the challenges at the end of the product life cycle. In order to come one step closer to a truly circular economy for functional textiles, Swijin participates in the Yarn-to-Yarn® pilot project of Rheiazymes AG as a lighthouse partner. This biotech solution uses microorganisms and enzymes to generate new starting materials directly from used textiles in a climate-neutral way. When customers return end-of-life Swijin products – for which the company offers incentives – the high-quality monomers can be returned to the supply chain in their original quality: true circularity.

"As an emerging brand, we have both the obligation and the luxury of choosing partners whose vision and values align with our own," says Claudia Glass. "I had a clear understanding of what kind of brand I would buy, but I couldn't find it anywhere. With Swijin, we feel obligated to actually make our values a reality."

The international OEKO-TEX^® Association, which consists of a total of 17 independent research and testing institutes in Europe and Japan, turns thirty this year. As one of the founding members, OETI is taking this as an opportunity to talk to OEKO-TEX^® expert Helene Melnitzky (Head of the Ecology Department at OETI) about the role of the OEKO-TEX^® Association, market trends and current OEKO-TEX^® certifications and labels.

The international OEKO-TEX^® Association is celebrating its thirtieth anniversary this year. What role has it played so far with regard to the product safety of textile and leather products?
Helene Melnitzky: In the area product safety¹, OEKO-TEX^® has had a great impact over the last three decades by ensuring certain pollutant additives, some of which were found in large quantities in textiles 30 years ago, no longer exist. The OEKO-TEX^® Association was also the first to limit certain heavy metals. Based on our actions, legal provisions were ultimately passed. We have been testing banned dyes since before there even was an EU regulation in this regard. Of course, we now test according to the EU regulation, but in this respect OEKO-TEX^® was a clear trailblazer.

In addition to product safety, OEKO-TEX^® has been working on the topics of ‘environmentally friendly textile products manufactured under fair working conditions for 30 years, which also included leather products for the last five years, and with STeP by OEKO-TEX^® on the ‘certification of environmentally friendly production sites’ since 2013. In one way or another, we have been preparing the market for thirty years. In the process, we are always creating new things: currently the Impact Calculator and, in autumn-2022, a new certification for brands and retailers: RESPONSIBLE BUSINESS by OEKO-TEX^®.

How does that benefit the customers of OEKO-TEX^®?
Helene Melnitzky: Customers can use these calculations for external communication to demonstrate on their products or webpages that their products have a lower footprint than their competitors. This means that customers sourcing everything regionally will have a smaller footprint than companies that source products from different countries. In the future, it will be necessary to display the water and carbon footprint on the product, so that consumers can decide whether they want to buy product A or B.

How is the aspect of fair working conditions taken into account?
Helene Melnitzky: This topic has also been gaining significant momentum over the last ten years. There is now enough pressure on brands and retailers to improve local working conditions. We cover this area as part of our STeP by OEKO-TEX^® certification² with our ‘social responsibility’ module. The advantage for our customers is that they can subsequently use the MADE IN GREEN by OEKO-TEX^® label to show how they have performed in the social module.

What does Transparency with MADE IN GREEN by OEKO-TEX^® mean?
Helene Melnitzky: Everything that is written on the product is transparent. The MADE IN GREEN by OEKO-TEX^® label is a traceable product label for all types of textiles and leather items that have been produced in environmentally friendly factories and at safe and socially responsible workplaces. Furthermore, the MADE IN GREEN by OEKO-TEX^® label gives consumers the certainty that the textile or leather product is made from materials tested for harmful substances. In order to ensure that textile or leather products with the MADE IN GREEN by OEKO-TEX^® label have been produced using environmentally friendly processes under socially acceptable working conditions, manufacturing and wet production sites must be certified according to STeP by OEKO-TEX^®.

For a year now, it has been possible to have recycled materials STANDARD 100 certified and display that certification as a hangtag to communicate that the product consists of a certain proportion³ of recycled materials. Which market demand is this certification addressing?
Helene Melnitzky: There is an increasing demand that at least part of the product must be made from recycled material. This is partly attributable to market pressure because raw materials are scarce and expensive. However, we are also voluntarily informing consumers about recycling as part of the circular economy.

What is your outlook for the next few years?
Helene Melnitzky: Producing textile and leather products in a more environmentally friendly and fair manner, while making the value chain more transparent, is a global challenge that sets new environmental standards. In the long term, however, it also involves important economic and social aspects. The goal is to raise awareness of these interdependencies and a common understanding of environmental issues – among producers and, of course, end consumers. It is clear that the demand for certified and traceable products is growing among consumers. This trend is reflected in purchasing behaviour and thus in manufacturing. Nevertheless, there’s still a lot to do.

¹ STANDARD 100 by OEKO-TEX^® und LEATHER STANDARD by OEKO-TEX^®
2 The STeP by OEKO-TEX^® certification includes the modules Chemical Management, Environmental Performance, Environmental Management, Quality Management, Occupational Health and Safety, and Social Responsibility
³ To qualify, the product must contain at least 20 per cent recycled material.

When it comes to the future of motorized mobility, everyone talks about the power drive: How much e-car, how much combustion engine can the environment tolerate and how much do people need? At the same time, new powertrains place ineased demands not only on the engine, but also on its housing and the car body: Carbon fibers are often used for such demanding applications. Like the powertrain of the future, the materials on the vehicle should also be environmentally friendly. That is why recycling of carbon fibers is required. Institutes of the Zuse Community have developed solutions for this.

Carbon fibers consist almost completely of pure carbon. It is extracted from the plastic polyacrylonitrile at 1,300 degrees Celsius, using a lot of energy. The advantages of carbon fibers: They have almost no dead weight, are enormously break-resistant and sturdy. These properties are needed, for example, in the battery box of electric vehicles in structural components of a car body.

The Saxon Textile Research Institute (STFI), for instance, is currently working with industrial partners on combining the static-mechanical strengths of carbon fibers with vibration damping properties to improve the housings of electric motors in cars. The project, which is funded by the German Federal Ministry for Economic Affairs and Energy, is aimed at developing hybrid nonwovens that contain other fibers, in addition to carbon fiber, as a reinforcement. "We want to combine the advantages of different fiber materials and thereby develop a product that is optimally tailored to the requirements", explains Marcel Hofmann, head of department of Textile Lightweight Construction at STFI.

The Chemnitz researchers would therefore complement previous nonwoven solutions. They look back on 15 years of working with recycled carbon fibers. The global annual demand for the high-value fibers has almost quadrupled in the past decade, according to the AVK Industry Association to around 142,000 t most recently. "Increasing demand has brought recycling more and more into focus", says Hofmann. According to him, carbon fiber waste is available for about one-tenth to one-fifth of the price of primary fibers, but they still need to be processed. The key issue for the research success of recycled fibers is competitive applications. STFI has found these not only in cars, but also in the sports and leisure sector as well as in medical technology, for example in components for computer tomography. "While metals or glass fibers cast shadows as potential competing products, carbon does not interfere with the image display and can fully exploit its advantages", explains Hofmann.
 
Using Paper Know-How
If recycled carbon fibers can pass through the product cycle again, this significantly improves their carbon footprint. At the same time it applies: The shorter the carbon fibers, the less attractive they are for further recycling. With this in mind, the Cetex Research Institute and the Papiertechnische Stiftung (PTS), both members of the Zuse Community, developed a new process as part of a research project that gives recycled carbon fibers, which previously seemed unsuitable, a second product life. "While classic textile processes use dry processing for the already very brittle recycled carbon fibers in fiber lengths of at least 80 mm, we dealt with a process from the paper industry that processes the materials wet. At the end of the process, in very simplified terms, we obtained a laminar mat made of recycled carbon fibers and chemical fibers", says Cetex project engineer Johannes Tietze, explaining the process by which even 40 mm short carbon fibers can be recycled into appealing intermediates.

The resulting product created in a hot pressing process serves as the base material for heavy-duty structural components. In addition, the mechanical properties of the semi-finished products were improved by combining them with continuous fiber-reinforced tapes. The researchers expect the recycled product to compete with glass-fiber-reinforced plastics, for example in applications in rail and vehicle construction. The results are now being incorporated into further research and development in
the cooperation network of Ressourcetex, a funded association with 18 partners from industry and science.

Successful Implementation in the Automotive Industry
Industrial solutions for the recycling of carbon fiber production waste are being developed at the Thuringian Institute of Textile and Plastics Research (TITK). Several of these developments were industrially implemented with partners at the company SGL Composites in Wackersdorf, Germany. The processing of the so-called dry waste, mainly from production, is carried out in a separate procedure. "Here, we add the opened fibers to various processes for nonwoven production", says the responsible head of the department at TITK, Dr. Renate Lützkendorf . In addition to developments for applications e.g. in the BMW i3 in the roof or rear seat shell, special nonwovens and processes for the production of Sheet Molding Compounds (SMC) were established at TITK. These are thermoset materials consisting of reaction resins and reinforcing fibers, which are used to press fiber-plastic composites. This was used, for example, in a component for the C-pillar of the BMW 7 Series. "In its projects, TITK is primarily focusing on the development of more efficient processes and combined procedures to give carbon fiber recycling materials better opportunities in lightweight construction applications, also in terms of costs", says Lützkendorf. The focus is currently on the use of CF recycled fibers in thermoplastic processes for sheet and profile extrusion. "The goal is to combine short- and continuous-fiber reinforcement in a single, high-performance process step."

1) Since February 1st, 2021, Dr.-Ing. Thomas Reussmann succeeds Dr.-Ing. Renate Lützkendorf, who retired 31 January.