Textiles can be coated with the biopolymer chitosan and thus made water-repellent by binding hydrophobic molecules. This can also replace toxic and petroleum-based substances that are currently used for textile finishing. The Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB, Stuttgart/Germany, and partners in the HydroFichi (Hydrophobic Finishing with Chitosan) project have researched how this can be done: A technology has been developed to provide fibers with the desired properties using biotechnological processes and chitosan.
Researchers have developed a way of producing chitosan from waste streams and using the biopolymer not only as a sizing agent in the processing of yarns, but also for the functionalization of textiles in the finishing process.
Chitosan is a renewable raw material that is derived from chitin; after cellulose, it is the second most common naturally occurring biopolymer. The properties of chitosan can be individually adapted by choosing the appropriate conditions. In sizing, for example, the effectiveness was shown in the significantly lower roughness of the yarns after weaving textile fabrics. In addition to simple coating with chitosan, which protects the fibers, the substance could be used as an anchor molecule to create cross-linking points for a wide variety of functional groups and thus to provide textiles with specific properties such as making them water-repellent. Chitosan can therefore function as a matrix material or template at the same time, and this can be done with a wide variety of fiber materials.
The values achieved with chitosan from insects were comparable to those from commercial crab shells. In the future, this fact will enable completely new possibilities of extraction in line with the bio-economy.