BioFibreLoop: Bio-inspired, laser-based functionalisation on bio-based materials leads to recyclable functional garments.
The EU textile industry is at a crucial turning point in terms of sustainable production and rapid adaptation to consumer demand for smart functions. The production of functional textiles often uses chemicals that cannot be recycled, which poses new challenges for the EU textile industry due to increasing regulations and strict bans on hazardous chemicals. Therefore, smart innovations are needed to help the textile industry eliminate the use of harmful chemicals and reduce its carbon footprint. BioFibreLoop will develop such innovations.
The paper presents the first results of the projects. It covers the specification, selection, development and production of textiles, the lignin-based coating, the development of appropriate digital tools, the safety and sustainability framework and finally some considerations on the industrial demonstration later in the project, before concluding with some information about the project.
Innovative textiles
The BioFibreLoop project is developing functional textiles made from renewable and recyclable raw materials (lignin, cellulose, and polylactide (PLA)). To protect these textiles from liquids, gases, UV light, and bacteria, a thin lignin coating is applied to the textile surface. The project is also developing a novel, highly environmentally friendly surface treatment to give the lignin coating increased water and oil repellence beyond its natural material properties.
In the first year of the project, the German Institutes for Textile and Fibre Research successfully spun fibres from lignin blended with a suitable cellulose that increases suppleness and strength, in three development stages. A particular challenge was the limited availability of suitable base lignin types from suppliers in wood refineries in Europe. Small companies founded a few years ago with special high-quality lignin types no longer exist, and larger ones often do not produce the required grades.
However, with new wood refinery plants currently being built or commissioned in Europe, we are very confident that a good supply of base lignin of correspondingly high quality will be available in the near future. Spinning continuous fibres in the melt-spinning process places high demands on homogeneous compounding and the rheological behaviour of the melt. If everything is perfect, multifilament with common textile counts can be spun and drawn. The slightly brownish, fine, and smooth continuous fibres exhibit a slightly shimmering sheen in the small sample fabrics produced . Further work on chemically modifying the lignin/cellulose blends is planned to increase fibre-related strength.
Further textiles made from other renewable raw materials are produced by European textile partners FreyZein, TecnoTex, and NIL Textile as woven, knitted, and nonwoven fabrics. These fibres consist of cellulose (mostly also derived from wood, regenerated cotton), and polylactic acid (PLA) from corn starch. Numerous textile samples were produced with variations in fibre composition, basis weight, and longitudinal and transverse stress-elongation behaviour. These samples were evaluated, and a portion of the selected variants was used to produce larger samples on industrial equipment for lignin coating development. After washing, these samples are cut into narrow strips for DITF’s smaller laboratory facilities.
To coat textiles, films are produced at the DITF from a mixture of lignin and cellulose. Here, too, the particular challenges initially lay in the extensive screening of European raw material suppliers and the evaluation of the biopolymers with regard to film-forming capacity, compound grain size, extensibility, and melting point. Three selected compounds with the required good properties are now available. With regard to recycling, we are focusing on a coating mixture that is the same or similar to that used for fibre production. When the coating and textiles use the same material, recycling is fundamentally much easier, as complex separation processes can be avoided. Thermal recycling with melting, cleaning, and reuse in fibre and coating production is, therefore, fundamentally possible.
These films are produced in a laboratory extruder with a slot die. In a subsequent step, these base films are modified with variable thicknesses and uniform properties on heated calanders. The coating onto the textiles takes place in a lamination process, in which the film and the textile are heated and thus thermally bonded. The particular challenge here lies in the development of the process technology, as the melting temperatures of the lignin films are the same or similar to those of the lignin fabrics (approx. 180°C) or can be even higher, for example, compared to PLA textiles. Despite this challenge, laminations can also be achieved on PLA nonwovens with good adhesion, so that the open 3D structure of the nonwovens is retained.
Furthermore, BioFibreLoop is demonstrating progress in the development of new technology for creating water- and oil-repellent surfaces. To this end, the participating researchers and staff members intensively analysed previously known surface structures of selected plants and fish. The micro- and nanostructures on the surface cause the aforementioned functional properties. From these findings, a physical theoretical model was derived to better understand the relationships between micro- and nanostructures and the properties of the liquids to be repelled. The major challenge now lies in transferring these structures to the surfaces of the lignin coating using a novel, laser-based embossing process.
The laboratories of ALPHANOV in France and the DITF are already conducting intensive research into metallic surfaces for transfer, special laser technologies, and the many variations of embossing techniques. Two different types of lasers are used to create the required topographical details on metal surfaces. These surfaces are transferred to the coated textiles in an embossing process under the influence of temperature and pressure. Contact angle measurements with water and diiodomethane show a tremendous increase in water and oil repellence through such structuring.
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