The SKZ plastics center, together with the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM, is launching the new CloseT research project focused on sustainable recycling of used textiles. The aim of the initiative is to develop an innovative continuous chemical recycling process for mixed textile fiber waste using solvolysis and to adapt it to industrial conditions. The solution to be developed is intended to enable direct use of the resulting reaction products as raw materials in plastics processing, aligning with the principles of the circular economy in the polymer sector.
Until now, used textiles have predominantly been sent to thermal recycling, in which valuable polymer resources are irretrievably destroyed. This method of managing textile waste limits the potential for their renewed material use. The CloseT project focuses on chemical recycling using solvolysis carried out in a continuous mode. Mixed textile fibers are to be chemically decomposed in a twin-screw extruder and then converted into feedstocks that can be reused in plastics processing. As project manager at SKZ, Dr. Hatice Malatyali, emphasizes, the goal is to create a sustainable alternative that, on the one hand, enables resource savings and, on the other hand, opens up new value chains for the plastics industry.
Assumptions of the solvolysis process and material separation
The project work begins with the development of suitable synthesis routes under laboratory conditions. At this stage, the parameters of the solvolysis process and the chemical reactions enabling efficient decomposition of individual components of mixed textiles are defined. The solutions developed are then to be transferred to a continuous process conducted in a twin-screw extruder. This configuration allows intensive mixing, precise temperature control and appropriate residence time of the material, which is crucial for stable and reproducible chemical reactions on an industrial scale.
One of the main research areas is the efficient separation of mixed fibers, in particular systems such as cotton and PET, which often occur together in clothing and technical textiles. Cellulose acetate is to be synthesized from the cellulose fibers obtained from the cotton fraction. The degraded PET fractions, in turn, are to be repolymerized to rPET, which can be used as a raw material in further plastics applications.
Both product streams, cellulose derivatives and rPET, are to be defined so that their properties are compatible with existing plastics processing operations. This requires selecting appropriate reaction conditions, chemical agents and parameters of the continuous process, so that the resulting materials can be incorporated into supply chains as secondary raw materials with reproducible quality.
Importance for the circular economy
Chemical recycling of textiles implemented under the CloseT project has the potential to reduce the volume of textile waste sent for incineration and to decrease the consumption of primary polymer raw materials. The use of solvolysis in a continuous process enables the recovery of complex fiber blends that have so far been difficult to manage using mechanical methods. According to Prof. Dr. Andreas Hartwig from the Fraunhofer IFAM institute, the project represents an important contribution to reducing textile waste and strengthening the circular economy.
An important element of the initiative is the direct integration of the recovered reaction products into plastics processing value chains. This approach minimizes the number of intermediate stages and can translate into more efficient use of resources and more stable economic conditions for secondary polymer raw materials. At the same time, the project creates a basis for developing new business models in textile recycling and for the use of recovered components in the production of plastic products.
Funding and schedule of the CloseT project
The CloseT research project, reference number 9D867, has received funding from the Volkswagen Foundation under the grant initiative "Circularity with Recycled and Biogenic Raw Materials". The project implementation period is scheduled from November 1, 2025, to October 31, 2029. SKZ – KFE gGmbH and the Fraunhofer IFAM institute emphasize the importance of the support provided by the Volkswagen Foundation for the development of new solutions in the field of chemical recycling and express their thanks for the funding granted.
The project results may form the basis for further research and development work on the implementation of chemical recycling of textiles on an industrial scale and on the integration of recovered raw materials into existing value chains of the plastics industry. This will help to strengthen links between the textile sector and the polymer industry, supporting the development of solutions in line with the principles of sustainable development.
Sampling of reaction products from the continuous chemical recycling process. (photo: Luca Hoffmannbeck, SKZ)
