Scientists have praised the lotus leaf as its highly repellent properties, and self-cleaning properties, for years. There have been many attempts to mimic the structure of the leaf in textile fibres and fabrics, and other repellent structures in nature have, and are, being looked at such as the butterfly wing. Repellency is affected by both the chemical application on to the fabric and the topography of the surface, in terms of roughness and structure. There have been research studies which include both surface structure and repellent chemistry. In brief, non-chemical approaches are being researched in many ways but their durability needs to be considered. HeiQ are a Swiss Materials company which are looking to repellent surfaces found in nature.
Our own experience tells us through laboratory studies that physics DWR (dendrimers) have worse durability than chemical DWR e.g fluorinated chemistry, but that depends on how these DWRs are applied such as
I have seen some recent papers on mechanical techniques for modifying surface structure...research at this point. To be sure lots of surface structure changing techniques are widely used to modify the aesthetics of textiles (think stone washed jeans). For sure, we have much to learn from how nature so easily and beautifully constructs surfaces to serve its purpose.
Bob - helpful comment. And I think this follows on Matt's comment that durability is also an important performance characteristic, particularly for brands like Patagonia where longevity reduces waste (increasing service life. Context seems to be really important here and of course complexity of supply chain changes.
Highly fluorinated side chain polymers have unique oleophobic and hydrophobic properties, which provide extremely
low surface tension and consequently oil repellent properties. This cannot be achieved with other groups of chemicals. If so called non fluorinated alternative polymers are used, they may achieve water repellent properties but not oil repellent properties due to their higher Surface energy.
Great question, Joel. Consumers range in their level of understanding about the chemistries themselves or even the term DWR, but all of them want the garment that they buy to do what it's supposed to do. That could be keeping them warm and dry in high exertion Alpine activities, or it could be retaining its vibrant color over a reasonable lifetime. Surface treatments go further than water repellency or beading -- stain repellency in low denier, lightweight down jackets or other non-waterproof/resistant styles is crucial as well.
In the case that a garment fails to meet the consumer's expectations, you can bet that we'll hear about it and act on it!
Sure. the supply chain is lit up on this topic as the focus on chemicals that should be used (preferred) and not used (restricted) evolves toward concerted action that involves transparency of the chemicals used by suppliers to brands. What I have learned is that when the importance and urgency is made clear by brands to suppliers and chemical suppliers, there is a will to act. The common ask that is the Higg® Index and tools developed by the ZDHC like the MRSL are really helping align thinking and most important, action. It's good business and growing. A most hopeful sign.
This is an interesting, and ongoing, area of research as Stefan comments. There are many possible pathways throughout the life of your raincoat but not one known main way. Some research, to-date, has looked into the emissions in wastewater and in air, but it is largely dependent on the consumers use of the garment - how frequently it is laundered etc. The research at the University of Leeds is investigating this further over a longitudinal study, using variables such as wash temperature and methods of heat treatment researched to be used by consumers. The effluent wastewater will be studied for traces of fluorinated compounds.
Since many industries use fluorinated compounds in their finishing and processing, research studies assessing sea water, emissions to air and health studies cannot be directly linked to outdoor apparel. The outdoor industry contributes to only a small percentage of the overall usage of fluorinated compounds. Research studies have focused on localized population samples. Due to the use within many industries, there is a undefined numbers of derivatives of PFASs, or fluorinated compounds, and the movement of these within the environment is somewhat unknown.
Some aftercare treatments were traditionally fluorine based, and this may also have been a method of exposure.
It must also be mentioned that analytical techniques for detection are continually developing.
This is THE challenge/opportunity. My experience tells me that you need to know specific people and get those people together in order to drive change and new technologies. To be sure, Brands need to be a loud and active voice to propel new technologies. Direct conversations between Brands and chemical companies is necessary but not sufficient. All the supply chain partners need to be known and engaged. This is different and there is a lot of trust that needs to be in place. Let's start building!
Is there any sense that perhaps major companies coming together to fund some intensive research on this topic would more quickly move the technology forward than the current silo-ish approach? Or is the competition landscape between brands such that a cooperative effort would not be realistic?