What is a coating? What is it used for in general? What are the applications in BioFibreLoop?
“Coating is a part of textile finishing. A coating layer on a textile substrate brings special functions into and onto a textile and therefore provides added value. Many technical textiles are coated in order to fulfil their special function. Such functions include, for example protection against liquids, gases, bacteria, but also protection of the textile itself against environmental influences and premature destruction. In our project we use the coating to repel water and oils, but also bacteria.”

How do you produce a coating in textile industry from obtaining the material to the finished coating?
“Coating is carried out with different processes: A water-based formulation is often used for thin and very thin coatings on fibres. However, this has to be dried in an energy-intensive manner. For slightly thicker coatings, coatings can be made with fusible materials. Drying is not necessary and saves a lot of energy. Both processes have advantages and disadvantages and have to be adapted to the textile and desired functions. In BioFibreLoop, we are using lignin in mixtures with cellulose as a melt product. The mixture is melted and applied to the carrier textile as a thin film.”

Which are the challenges of producing coatings in BioFibreLoop?
“The challenges lie in meeting the necessary durability requirements in the various targeted applications. For example in the case of protective textiles, a high number of washing cycles must be possible and therefore a high abrasion resistance. A particular scientific challenge is achieving water and oil repellency without the use of environmentally harmful perfluorocarbons which are usually used for oil-repellent functional textiles.

Here in BioFibreLoop, we are focusing on a bionic approach from living nature: special surface structures on fish and other living creatures show oil repellency. We want to understand these structures well in the project and transfer them to our technical coatings via an embossing process on the lignin-cellulose coatings.”

What are benefits of the lignin coating developed in BioFibreLoop compared to commercially available comparable coatings for textiles?
“The coated textiles in our project will all be biodegradable. This means that they will no longer contribute to the major environmental problem in our waters caused by microplastics. Despite the biodegradability, we are working on making the textiles so robust that recycling the materials is possible and economically sensible. In this way, we meet several of the requirements of the new EU regulation in the frame of the “Green Deal”, which will soon make textile production much more sustainable.”

Please give a vision. How will BioFibreLoop’s innovations regarding the coating affect the textile industry of tomorrow?
“The new lignin-based coatings make it possible to produce a textile material without petrochemical polymers altogether. Lignin is a highly abundant material, as it originates from wood growing in large quantities in Europe. It is widely available as a byproduct of the paper production process. At the same time, this biopolymer is very robust, so that in future numerous technical applications are possible in addition to clothing.

Furthermore, environmentally harmful polymers, which have previously been required to achieve water and oil repellency, can be dispensed with. 

If developments in this project are successful, there will be many opportunities in the textile industry to develop products that are made entirely from renewable raw materials, are recyclable and ultimately completely biodegradable.”