Hydrofichi – Bio-based hydrophobic and dirt-repellent finish for the substitution of pPerfluorochemicals (PFCs) on textile surfaces with chitosan derivatives

Challenge

In the past, enzymes and renewable raw materials played a minor role in textile processing. Although they have been used, for example, to size and desize textiles, only a small proportion of them are currently used in textile finishing – compared with the large number of petrochemical products and textile auxiliaries. The Hydrofichi project not only demonstrates the great potential of the biopolymer chitosan for the efficient hydrophobization of textiles, but also defines further promising areas of application for the polysaccharide in textile processes.

Chitosan – readily available hydrophobic biopolymer

Chitosan can be isolated from fishery waste as well as from side streams of insect cultivation or explicitly from microorganisms. Chitosan is also already offered and partly used as a biobased and environmentally friendly sizing agent in the textile industry. Due to its chemical structure, the renewable biopolymer is well suited for derivatization and coating.

Tailor-made functionalization as a hydrophobizing agent

The specific functional groups of the chitosan molecule allow to optimally adapt the properties of the textile surfaces with regard to a maximum hydrophobic equipment. In the Hydrofichi project, we have tailored functionalization of the biopolymer chitosan for use as a hydrophobizing agent.

In laboratory tests, the textile fabrics coated by Fraunhofer IGB showed significant hydrophobicity after finishing. Chitosan was successfully integrated into the textile finishing processes and was partly essential as a template for hydrophobicity. In the course of our investigations, the chemical and biotechnological functionalization of chitosan with a wide variety of biobased reactants was optimized. Enzymes were also used for the first time for hydrophobic finishing of the fabrics. They therefore represent a unique selling point in the hydrophobization of textiles.

The evaluation of the finishes was carried out by means of standardized tests but also with specially designed test rigs and methods. Contact angle measurements with values of over 140° and water repellency confirmed the successful finishing.

Application spectrum of efficient chitosan formulations from textiles to medical technology

The highly efficient and at the same time sustainable chitosan formulations developed in the project can replace fossil-based components for textile finishing. The biobased hydrophobic chitosan derivatives are not only used as tailor-made components for textiles, but can also be of interest for medical technology due to their antimicrobial and hydrophobic effect, for example in prostheses and implants or as coatings for plastics and metals.

Outlook

From the point of view of the textile industry, the end of the line has not yet been reached for chitosan as an anchor molecule for water repellency. On the contrary, studies show that the polysaccharide can be used as a substitute for synthetic polymers in a wide variety of textile processes. The IGB will therefore continue to focus on modifying the chitosan molecule and optimizing formulations in order to develop biobased marketable products. This will make it possible to replace other petrochemical processes in the textile industry with new bioeconomic products.