Waterproof outdoor clothing Plasma Coatings Could Help Outdoor Clothing Ditch PFAS

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Empa researchers are working with Swiss textile partners on PFAS-free coatings for waterproof outdoor clothing. Using a new plasma coating process, the EC0Tex project aims to apply fluorine-free substances more precisely to textile yarns, reducing chemical use while maintaining water-repellent performance in line with safe and sustainable design principles.

Hiking, jogging, biking — when enjoying outdoor activities, it’s easy to get caught off guard by unexpected weather. Modern performance clothing can be waterproof and stain-resistant, but it is often treated with chemicals containing PFAS. It’s not easy to find alternatives to these harmful substances. Researchers at Empa are therefore working with textile manufacturers to develop a technology that can be used to find substitutes for PFAS and apply them more precisely — in line with the Safe and Sustainable by Design principle.

Chemical treatment is necessary to ensure that functional clothing can withstand all weather conditions. However, rain jackets, swimsuits, and other items with a PFAS coating contribute to environmental pollution with these fluorine-containing forever chemicals. Replacing this group of substances is no easy task, as they have excellent properties: PFAS are water, dirt, and grease repellent. Empa researchers are therefore working with industry partners to develop technologies and materials that can be used to produce PFAS-free textiles with the desired properties in a sustainable and economical way. This innovative initiative originated from the Subitex network, a long-standing collaboration between companies affiliated with the Swiss Textiles Association and Empa in St. Gallen. The Innosuisse-funded EC0Tex project aims to produce water-repellent coatings for textile yarns by using fluorine-free substances in a specially developed plasma coating system. The project was recently honored with the “Innovation Award” for sustainability and innovation at the “Techtextil” international trade fair in Germany’s Frankfurt am Main.

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Substitutes without regret

The Safe and Sustainable by Design framework, or SSbD for short, is central to the EC0Tex project. “When searching for alternatives to PFAS, it is important not to create so-called regrettable substitutes, i.e., substitutes that turn out to be just as harmful as the chemical originally used,” says Empa researcher Dirk Hegemann from the Advanced Fibers Laboratory in St. Gallen. Therefore, a team led by Dirk Hegemann, Martin Amberg, and Patrick Rupper weighs the needs of industry, the environment, and society against each other early on in the development process using risk analyses and the like and dismisses those materials and technologies that fail to meet the desired properties, sustainability, or economic efficiency criteria.

Coated to the core

Together with partners from the Swiss textile industry Bäumlin & Ernst, Lothos KLG, and Seilfabrik Ullmann, a novel industrial-grade coating process using plasma technology is being developed. This is because PFAS-free substances would have to be used in excessive quantities with conventional techniques in order to achieve the properties of PFAS-coated textiles — which would drastically reduce their cost-effectiveness and sustainability, making the search for viable alternatives according to SSbD standards a challenge.

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The new plasma system, which was designed for this very purpose in collaboration with Empa researchers, makes it possible to apply extremely thin coatings to the individual fibers in a yarn. “This allows us to significantly reduce the amount of chemicals while achieving comprehensive impregnation of the yarns,” says Hegemann. The yarns produced in this way could be used directly in the production of outdoor and sportswear, as well as ropes, according to the researcher.

In plasma-induced coating technology, plasma is generated in a chamber by means of an electric gas discharge. Since this provides high energy at low temperatures, the chemicals in the chamber evaporate and form reactive species that attach themselves to the individual fibers of a yarn. However, this usually only allows the outermost fibers of a textile to be impregnated. “We have taken a new approach: The new plasma coating system generates different reactive species that can also penetrate deep into the yarn structure,” explains Hegemann. This results in a durable and penetrating coating.

The challenge: grease and dirt

As an alternative to PFAS, researchers are now investigating how organosilicon compounds can be used for impregnation. The safety of these compounds, even when released into the environment through abrasion or washing, must be analyzed in detail. Initial studies show that organosilicon compounds form highly cross-linked layers with excellent water-repellent and quick-drying properties that even surpass those of PFAS coatings in terms of durability.

One challenge that remains is the grease and dirt repellency that PFAS textiles can achieve. According to Hegemann, further work is needed to replace PFAS in special textiles such as protective workwear. The large group of organosilicon compounds opens up a wide range of possibilities here. Thanks to plasma technology, it is now also possible to find additional new solutions by adjusting the initial substances and coating conditions and tailoring them to the desired properties of the textiles — while at the same time keeping the SSbD principles in mind.

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