A current research proves that highly cross-linked siloxanes are a safe and effective alternative to PFAS by providing textiles with durable and strong hydrophobic properties without harming the environment.

Rain jackets, swimming trunks or upholstery fabrics: textiles with water-repellent properties require chemical impregnation. Although fluo rine-containing PFAS chemicals are effective, they are harmful to health and accumulate in the environment. Empa researchers are now developing a process with alternative substances that can be used to produce environmentally friendly water-repellent textile fibres. Initial analyses show: The “good” fibres repel water more strongly and dry faster than those of conventional products.

If swimming trunks are to retain their shape after swimming and dry quickly, they must combine two properties: It must be elastic and must not soak up water. Such a water-repellent effect can be achieved in the textile industry by treating the textiles with chemicals that give the elastic garment so-called hydrophobic properties. In the 1970s, new synthetic fluo rine compounds began to be used for this purpose – compounds that seemed to offer countless application possibilities without hesitation, but later turned out to be highly problematic. This is because these fluorocarbon compounds, PFAS for short, accumulate in the environment and are harmful to health (see box). Empa researchers are therefore working with Swiss textile companies to develop alternative, environmentally friendly processes that can be used to give all fibres a water-repellent finish. Dirk Hegemann from Empa’s “Advanced Fibers” laboratory in St. Gallen explains the Innosuisse-funded project: “We use so-called highly cross-linked siloxanes, which produce silicone-like layers and – unlike fluo rine-containing PFAS – are harmless.”