In the last few months you may have noticed that a new Gore-Tex membrane has begun to enter the market. But what's the difference between this new technology and those that the brand have used to date? Well it's complicated.
At UKC/UKH we review products rather than testing them - by which I mean that we concentrate on how they perform as an end user out in the real world, not in a lab. But at the risk of getting academic, it's important to be aware of the background to the new Gore-Tex ePE membrane and its PFC-free DWR treatment if you're to understand why they have made the move, why brands are adopting it, and why it should be of interest and relevance to us when we next come around to buying a waterproof jacket.
Before we delve into the detail it's worth starting with the basics, namely what is 'Gore-Tex'?
This waterproof/breathable fabric is not just a single layer, nor the name of the waterproof membrane itself; it's the name given to the whole package, which consists of several layers working together: the lining or backer, the membrane, and the face fabric.
Each layer has a distinct role:
- The backer/lining helps to distribute the moisture built up inside the jacket across a wide surface area, enabling it to evaporate and pass through the membrane.
- The membrane's role is to let water vapour through from the inside whilst keeping water from the outside, out.
- The face fabric's role is to protect the membrane and give extra durability to the jacket.
In addition to these layers there is another which sits on the very top - the DWR (Durable Water Repellent) treatment. This plays a key role, providing a slippery layer on top of the face fabric which allows water to roll off it, as opposed to being absorbed by it - an effect known as 'beading'.
This treatment is not permanent, and once it's worn out a jacket's face fabric will begin to absorb water, whereupon it will 'wet out'. When a jacket wets out its breathability is reduced, meaning - in real terms - that you will start to feel the build-up of condensation on the inside. This dampness on the inside is often mistaken by the wearer as a membrane failure, but really it's just an indication that the DWR treatment needs refreshing (courtesy of a wash and proof with products such as Nikwax Tech Wash and TX Direct).
The Evolution of the GORE-TEX membrane
Until recently Gore-Tex exclusively used an ePTFE (expanded polytetrafluoroethylene) membrane. This is the product that they've built a reputation on since it was first released in 1976, and the one that has ultimately made them the industry leader. Traditional ePTFE technology, and the DWR treatment that augments it, contain PFCs (fluorocarbons). These 'forever chemicals' don't break down and, in the case of DWRs, as a result of this they build up not just in the natural environment, but within living organisms too - ourselves included. The GORE-TEX membrane itself is not considered a health concern (as independently certified by Oeko-Tex and bluesign), as it is in a solid form and therefore does not break down in the environment. However, the negative health implications of this group of chemicals generally are nowadays better understood, and many industries - including the outdoor industry - are trying to reduce their use.
PFAS stands for Per- and Polyfluoroalkyl substances and describes a wide range of chemistries with very different properties and uses. Because there are clear and important distinctions between the more than 4,700 materials often referred to as PFAS, it is a very complex topic. Therefore, when communicating about PFAS, we believe it is important to be specific about the particular chemistries or type of PFAS being discussed. There are significant distinctions between the chemical and physical properties of fluoropolymers like PTFE and other materials most often associated with the term PFAS. PTFE does meet the very broad definition of the term despite the important distinctions. Often, agencies, regulators, scientists or media may use the acronym PFAS when the specific point being made is only accurate for certain PFAS, for example non-polymers such as PFOA. "PFAS" are, for example, described as mobile in the environment. PTFE, a fluoropolymer, is not mobile in the environment.
For more information download the PTFE Fact Sheet.
In response to a growing demand for PFC-free products from brands and end users, as well as in anticipation of changes to regulation, the company began the development ten years ago of ePE (expanded polyethylene). The result of this decade-long process is a completely new membrane, with a completely different structure. In tandem, Gore have also developed - and released - a PFC Free DWR treatment, which has been available since 2018, and is now used throughout 50% of their fabrics. Both these essential components of the waterproof/breathable fabric are PFC-free. Gore have also raised the bar in terms of using more sustainable materials, with both the backer and the face fabric of ePE jackets being constructed using recycled and/or solution dyed materials - the former reducing waste, the latter reducing the amount of water and energy required to make it.
On a practical level, ePE has a better strength to weight than ePTFE meaning that the membrane can be both lighter and thinner, which is part of the reason it has a lower carbon footprint. This gives jackets that feature ePE a slightly softer feel than their ePTFE equivalent. Most critical of all from a staying dry perspective, the ePE membrane has the same super high hydrostatic head, meaning it's equally suitable for the worst weather.
So far, so good for the planet. But there is an implication for the end user.
PFCs, awful though they may be, are extremely good at shedding water. Perhaps the most noticeable change for a wearer of any garment using PFC free DWR, will be the treatment's durability. This is simply not as effective, insofar as the 'durable' element of DWR is no longer as durable and the benefits don't last as long. But, on the bright side, the DWR treatment is significantly better for the environment.
Across the outdoor industry, the jackets of yesteryear (both Gore Tex and other brands) contained long-chain (C8) fluorocarbon based DWR treatments. These nasties were so effective at shedding water that you could get away without washing or proofing a jacket for a long, long time - in fact many people managed never to do so over a garment's lifespan. When the transition was made to a shorter-chain (C6) the most noticeable side effect in use was that your jacket's face fabric wetted out quicker, soaking up water rather than shedding it. While scientists continue to work on better solutions, with the currently available PFC-free DWR coatings the wetting out effect is unfortunately even more noticeable.
The way around this is to wash and reproof your jacket more often. This may require a slight change in expectation and mindset on the part of end users.
In real world terms, you're going to have to wash and proof your ePE jacket more frequently, not because of its ePE membrane, but because its PFC-free DWR treatment will wear off quicker than the equivalent C6 PFC DWR would have. Obviously this requires time and effort to do, but the benefits - aside from a performance perspective - are numerous, not least that your jacket should last longer as a result of the extra TLC it's been given.
The current crop of ePTFE and ePE fabrics will coexist alongside each other for some time to come - for instance ePTFE membrane will continue to feature in Gore Pro products, as a result of it still being the most durably waterproof option available for now. ePE will take over where Gore Performance once dominated, with a broader appeal to the all-round outdoor enthusiast, but in the long-term Gore-Tex have acknowledged ePE membrane as being the future trajectory for the brand, as it aligns with their sustainability goals. No doubt they will keep working on its performance - much like they have the rest of the range over the last 45 years.
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