Durable water repellents (DWRs) that provide liquid repellency to functional textiles are part of an ongoing global substitution process. The process of substitution was initiated after DWRs based on side-chain fluorinated polymers (long-chain SFPs) were identified to contribute to the diffuse release of long-chain perfluoroalkyl acids (PFAAs) to the environment. Long-chain PFAAs are organic contaminants that are extremely environmentally persistent, have a propensity to bioaccumulate, and are toxic to wildlife and humans. This thesis aims to support the substitution process by identifying alternative DWRs that combine functionality with a benign environmental profile. As part of the SUPFES project, a cooperation between academic and industrial research groups, several studies were conducted in a three-step approach to form a basis for an informed substitution process. This approach included practical tests of functionality (STEP 1) of DWR alternatives in different textile applications, experimental work and desk-based review of the literature to determine 13 hazard endpoints (STEP 2) and life cycle assessment (STEP 3). DWR alternatives were grouped into short-chain SFPs, silicones (Sis) and hydrocarbons (HCs). To profile their environmental behaviour, potential loss mechanisms that cause the release of critical (i.e. potentially hazardous) chemicals were estimated and confirmed experimentally.

The results showed that no DWR substitute provided a universal solution considering functionality (STEP 1) and the associated chemical hazard together (STEP 2). Short-chain SFPs exhibit high durabilities and repellency of liquids of all different polarities, but lead to the release of extremely persistent short-chain PFAAs. Some HCs are more environmentally benign in terms of human health and ecological risk, and show a high water repellency as well as durability, but do not repel liquids with very low surface tension. Thus, we suggest to choose DWR alternatives according to specific protection needs that are required in different segments of the textile market. For consumer outdoor clothing, that mainly require water repellency, a trade-off by using more environmentally friendly materials which do not offer complete stain repellency could be made. For other textile segments, such as protective work clothing, where no compromise of safety is possible, short-chain SFP substitutes are today the only viable option.

The loss of textile fibres from functional textiles and the degradation of the fibre-bound DWR coatings after their emission was identified to be a loss mechanism that leads to the long-term release of persistent contaminants. Fibre loss of short-chain SFP containing textiles, due to domestic washing, was characterised for size and amount as well as their total fluorine content. Results showed that the fibres lost can still contain the fluorinated DWR coatings and likely form a long-term emission source of PFAAs through their accumulation and slow degradation in the environment. These results provide further information for the life cycle assessment (LCA) (STEP 3).

The expected long-term environmental release of extremely persistent short-chain PFAAs, suggests that DWRs based on SFPs are not a sustainable substitution solution. Therefore, new concepts in textile technology are needed for a complete substitution of fluorinated DWRs. Our stepwise approach generates useful data to make an informed judgment about possible DWR alternatives and will together with the LCA provide much needed guidance in the substitution process.