To ensure functional clothing withstands all weather conditions, chemical impregnation is necessary. However, rain jackets, swimwear & Co with a PFAS-containing coating contribute to environmental pollution with these fluorine-containing forever chemicals. Replacing this substance group is not trivial as it possesses excellent properties: PFAS are water, stain, and oil-repellent. Therefore, Empa researchers are collaborating with industry partners to develop technologies and materials allowing the sustainable and economical production of PFAS-free textiles with the desired properties. This innovative endeavor emerged from the Subitex network, a longstanding collaboration between companies of the Swiss Textile Federation Swiss Textiles and Empa in St. Gallen. The project 'EC0Tex', funded by Innosuisse, aims to create water-repellent coatings for textile yarns by using fluorine-free substances in a specially developed plasma coating system. Recently, the project was awarded the 'Innovation Award' for Sustainability and Innovation at the international trade fair 'Techtextil' in Frankfurt am Main.
Replacement without Regret
Central to the 'EC0Tex' project is the 'Safe and Sustainable by Design' principle, or SSbD for short. 'When searching for alternatives to PFAS, it is crucial not to create so-called regrettable substitutes, which are replacements that later turn out to be as harmful as the originally used chemical,' says Empa researcher Dirk Hegemann from the 'Advanced Fibers' laboratory in St. Gallen. Therefore, the team around Dirk Hegemann, Martin Amberg, and Patrick Rupper aligns the needs of industry, environment, and society early in the development process using risk analyses, filtering out materials and technologies that fail in desired properties, sustainability, or economy.
Enveloped to the Depth
Together with implementation partners from the Swiss textile industry Bäumlin & Ernst AG, Lothos KLG, and Seilfabrik Ullmann AG, a novel industrial impregnation process using plasma technology is being developed. PFAS-free substances would need to be used in too large amounts with conventional techniques to replicate the material characteristics of PFAS-coated textiles. This leads to downsides in economy and sustainability, making the search for viable alternatives a challenge under SSbD standards.
The new plasma system, developed jointly with Empa researchers, allows extremely thin coatings to be applied onto the individual fibers within a yarn. 'This way, we can significantly reduce the amount of chemicals used while achieving a comprehensive coating of the yarns,' says Hegemann. The yarns produced this way could be directly used in the manufacturing of outdoor and sportswear, as well as ropes, according to the researcher.
In plasma-induced coating technology, plasma is generated in a chamber via electrical gas discharge. High energy provided at low temperatures leads to the evaporation of chemicals in the chamber, forming reactive species that attach to the individual fibers of a yarn. Usually, only the outermost fibers of a textile can be impregnated this way. 'We followed a new approach: The new plasma coating system generates differently reactive species, which can also penetrate deep into the yarn structure,' explains Empa researcher Dirk Hegemann. This results in a durable and penetrating coating.
Challenge: Oil and Stain Resistance
As an alternative to PFAS, researchers are now examining how silicon-organic compounds can be used for impregnation. The safety remains to be thoroughly analyzed, even under environmental exposure from abrasion or washing. Initial analyses show that the silicon-organic compounds form highly cross-linked layers with outstanding properties in terms of water repellency and quick-drying, even surpassing the resilience of PFAS impregnation.
A current challenge remains oil and stain resistance achievable by PFAS textiles. Further work is needed to replace PFAS in textiles like protective workwear, according to Hegemann. The large group of silicon-organic compounds offers a multitude of possibilities here. Thanks to plasma technology, there is now the opportunity to find further new solutions through adjustments in raw materials and coating conditions, tailored to the desired textile properties while keeping the 'Safe and Sustainable by Design' principles in focus.
Contact:
Dr. Dirk Hegemann
Advanced Fibers
Tel. +41 58 765 72 68
dirk.hegemann@empa.ch