#Research & Development

2023-11-02

Lignin coating makes geotextiles made from environmentally friendly natural fibers durable

Textiles are a given in civil engineering: they stabilize water protection dams, prevent runoff containing pollutants from landfills, facilitate the revegetation of slopes at risk of erosion, and even make asphalt layers of roads thinner. Until now, textiles made of highly resistant synthetic fibers have been used for this purpose, which have a very long lifetime. For some applications, however, it would not only be sufficient but even desirable for the auxiliary textile to degrade in the soil when it has done its job. Environmentally friendly natural fibers, on the other hand, often decompose too quickly. The German Institutes of Textile and Fiber Research Denkendorf (DITF) are developing a bio-based protective coating that extends their service life.

Depending on humidity and temperature, natural fiber materials can degrade in the soil in a matter of months or even a few days. In order to significantly extend the degradation time and make them suitable for geotextiles, the Denkendorf team researches a protective coating. This coating, based on lignin, is itself biodegradable and does not generate microplastics in the soil. Lignin is indeed biodegradable, but this degradation takes a very long time in nature.

Coating process of a cellulose-based nonwoven with the lignin compound using thermoplastic processing methods on a continuous coating line. Photo: DITF

Together with cellulose, Lignin forms the building materials for wood and is the "glue" in wood that holds this composite material together. In paper production, usually only the cellulose is used, so lignin is produced in large quantities as a waste material. So-called kraft lignin remains as a fusible material. Textile production can deal well with thermoplastic materials. All in all, this is a good prerequisite for taking a closer look at lignin as a protective coating for geotextiles.

Nonwoven fabric based on cellulose, coated with the lignin compound as a protective layer against degradation in the soil. Photo: DITF

Lignin is brittle by nature. Therefore, it is necessary to blend the kraft lignin with softer biomaterials. These new biopolymer compounds of brittle kraft lignin and softer biopolymers were applied to yarns and textile surfaces in the research project via adapted coating systems. For this purpose, for example, cotton yarns were coated with lignin at different application rates and evaluated. Biodegradation testing was carried out using soil burial tests both in a climatic chamber with temperature and humidity defined precisely according to the standard and outdoors under real environmental conditions. With positive results: the service life of textiles made of natural fibers can be extended by many factors with a lignin coating: The thicker the protective coating, the longer the protection lasts. In the outdoor tests, the lignin coating was still completely intact even after about 160 days of burial.

Textile materials coated with lignin enable sustainable applications. For example, they have an adjustable and sufficiently long service life for certain geotextile applications. In addition, they are still biodegradable and can replace previously used synthetic materials in some applications, such as revegetation of trench and stream banks.

Cotton yarns: with lignin coating as a protective layer against degradation in soil and reference material without coating. Photo: DITF

Thus, lignin-coated textiles have the potential to significantly reduce the carbon footprint: They reduce dependence on petroleum-based products and avoid the formation of microplastics in the soil.

Cross-section of a cotton yarn coated with lignin by extrusion process. Photo: DITF

Further research is needed to establish lignin, which was previously a waste material, as a new valuable material in industrial manufacturing processes in the textile industry.

DITF send a signal for climate protection

The German Institutes of Textile and Fiber Research Denkendorf (DITF) have successfully implemented extensive investments in photovoltaic systems at their site in Denkendorf. The systems installed on the roofs of the buildings and covered parking lots have a total installed capacity of 840 kilowatt peak (kWp). The DITF invested 1.6 million euros in this with the support of the state of Baden-Württemberg. The system was ceremonially put into operation on September 17, 2025.

4.2 million Euros for research into textile recycling

Around the world, used textiles are still rarely recycled and pile up into huge mountains of waste. A recent study by the Boston Consulting Group (BCG) drew attention to this problem. However, the low recycling rate is also due to the fact that only a small percentage of used textiles are actually suitable for recycling into high-quality materials and for demanding applications. The German Institutes of Textile and Fiber Research Denkendorf (DITF) are addressing this problem with their research.

Denkendorf fiber chart revised

A companion during studies and for practical use in the workplace: generations of textile experts have used the Denkendorf Fiber Chart to keep track of all the important characteristic values of textile raw materials. Following the first two editions in the 1970s and 1980s, Denkendorf scientists have comprehensively revised the Fiber Chart. The third edition is now available in digital form for the first time.

Carbowave: Energy efficiency in carbon fiber production

A new technology uses microwaves and plasma heating to produce carbon fibers in an energy-efficient manner. This means high-strength composite materials can be produced more cheaply and efficiently. The German Institutes of Textile and Fiber Research (DITF) are part of the Carbowave research consortium, which aims to improve and commercialize microwave and plasma-induced carbonization.

Aachen Summer School: Strengthening German-Korean cooperation in 4D and robotics

The Aachen Summer School has established itself as an important platform for promoting cooperation between RWTH Aachen University and Seoul National University. The focus is on practice-oriented research projects in the field of 4D and robotics technologies, which have been successfully implemented for years at the Institut für Textiltechnik of RWTH Aachen University.

Closing the Loop in the Textile Industry: Value Creation in the State of Brandenburg

How can the state of Brandenburg benefit from a circular textile industry? This question is addressed in the new policy paper "Closing the loop in the textile industry: Value creation in the state of Brandenburg." Based on the „TexPHB“ feasibility study funded by the Brandenburg Ministry of Climate Protection, it shows how textile waste can be integrated into new value chains.

Better, faster, bio-based: Functional new Plastic alternatives

How can new bio-based and biohybrid materials with improved features be developed faster? Six Fraunhofer institutes are jointly exploring this question in the SUBI²MA flagship project, using an innovative bio-based polyamide developed by Fraunhofer researchers as a model. Its specific properties make it a promising alternative to fossil-based plastics.

RE&UP debuts at Ecomondo 2025 to showcase circular fashion innovation

RE&UP makes its first appearance at Ecomondo – The Green Technology Expo, Europe’s leading event for ecological transition and circular economy. Specializing in textile-to-textile recycling, RE&UP transforms end-of-life fabrics into Next-Gen recycled cotton fibers and polyester chips, giving new life to materials that would otherwise go to waste.

ICAC announces postponement of the 83rd Plenary Meeting in Tanzania

Due to unforeseen circumstances arising from the recent developments in Tanzania, the ICAC has announced that its upcoming 83rd Plenary Meeting has been postponed. Scheduled for Nov. 17-20 in Mwanza, the delay was recommended by Tanzania, and the decision was made out of an abundance of caution, prioritizing the safety and well-being of all participants.