How GORE-TEX® membranes work

3. August 2018

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Today, GORE-TEX® is the epitome of waterproof and breathable garments. Regardless of whether you’re skiing, cycling, mountaineering at work or just going about your everyday life, you can always rely on the high-quality products engineered with GORE-TEX® membranes – at least that’s what the American brand claims. In the following, we’re going to have a closer look at the composition of this membrane and what makes it so special.

Bill Gore sees the potential of PTFE

Illustration of the membrane.

The membrane in the form of a glove.

The development of the GORE-TEX® membrane was more than just a lucky coincidence for the US chemist Bill Gore. Gore worked as a researcher at the chemical company DuPont in the 1950s, which has made a host of valuable contributions to the outdoor industry in the form of ground-breaking inventions and innovative fibres such as nylon, Lycra, Kevlar and neoprene. Interestingly enough, DuPont failed to see any benefit in continuing Bill Gore’s research on polytetrafluoroethylene (PTFE for short), but Gore did.

In 1958, Bill Gore realised his dream and founded his own company, W.L. Gore & Associates, Inc, which grew from a classic American start-up based in a cellar into a global corporation with over 10,000 employees. Bill Gore had initially dedicated his research to new applications for the electrical industry until his son Bob accidentally discovered ePTFE, the material used to make all our dreams of breathable & waterproof outdoor apparel come true.

By the way, the ePTFE membrane is not just used in waterproof gear – GORE’s portfolio includes industrial applications, medical implants (e.g. artificial arteries) and industrial applications based on the research into and development of PTFE and ePTFE.

From PTFE to ePTFE – from ePTFE to the GORE-TEX® membrane

Close-up of the membrane under the microscope.

This image shows the microporous structure. The red drops symbolise sweat, which can travel through the pores unhindered.

Since we and the majority of our readers are laypeople with limited knowledge in chemical processes, we thought it’d be best to explain how ePTFE was discovered like this: When Bob Gore was experimenting with PTFE, he yanked the material suddenly, discovering that it could stretch quite a bit without getting ruined. The expanded (i.e. “e” PTFE) material not only remained solid after stretching, but formed a microporous structure as well.

This microporous structure of expanded polytetrafluoroethylene is, of course, extremely small and not visible to the naked eye. However, you can see the large openings in the material under an electron microscope. There are about 1.4 billion of these tiny pores on a single square centimetre of the waterproof membrane. And as luck would have it, this pore size just happens to be ideal to guarantee both waterproof protection and breathability in functional clothing as well!

Much smaller than a water droplet and large enough for water vapour

Water vapour molecules are very small, much smaller than the pores in the GORE-TEX® membrane. The pores are even 700 times larger than the vapour molecules, so the latter can travel from one side of the membrane to the other unhindered. For the outdoor athlete, this means that the vapour from sweat can escape through the membrane, keeping you dry.

As for liquid water, water droplets are much larger than the pores in the GORE-TEX® membrane. In fact, the pore in the microporous membrane is about 20,000 times smaller than the smallest drop of water, so there’s no way it’s getting through those microscopic pores, even if there is a lot of them or you run into some heavy rains.

The GORE-TEX® membrane becomes a durable laminate

An expanded PTFE membrane looks like a thin, flexible plastic film. Even in its raw form, the membrane is already windproof, waterproof and breathable, but its strength has yet to reach the optimum level. Mechanical abrasion or damage caused by sharp objects can lead to holes through which water can penetrate.

Illustration of the Gore-Tex three-layer laminates.

All fabrics are bonded together in three-layer laminates.

This is why the GORE-TEX® membrane used for functional clothing, gloves and outdoor footwear must be made into laminate first. This means that the GORE-TEX® membrane is bonded to a backer material to form a single unit. For outdoor garments, the outer material used with membranes is usually a hard-wearing synthetic fabric made of either nylon or polyester. When bonded together, the outer material and membrane form a solid laminate. Fortunately, neither the breathability nor the waterproof properties of the fabric is affected as a result, which is due in large part to the careful choice of the outer fabric and excellent production processes.

Whether we refer to the laminate as a 2-layer or 3-layer GORE-TEX® laminate depends on the lining. The three-layer construction uses a lining that is bonded directly to the membrane from the inside. This means that the GORE-TEX® membrane is sandwiched between the outer material and the comfortable lining, providing optimum protection from dirt and damage from both sides. In contrast, a two-layer construction uses a separate lining.

The specific differences and characteristics of each of the GORE-TEX® products, such asGORE-TEX® Active, GORE-TEX® Pro, GORE-TEX® Paclite®, GORE-TEX® C-KNIT® or GORE-TEX® 2-layer products will be explained in detail at a later date. What we will say, however, is that some of the main differences between 2-layer and 3-layer laminates lie in their weight and strength. While ultra-light GORE-TEX® jackets for trail runners are made from lightweight laminates, those extremely tough expedition jackets designed for mountaineers are made from stronger, more durable laminates.

Getting the most out of a GORE-TEX® membrane

The finished laminates with integrated GORE-TEX® membranes are the basis for windproof, waterproof and breathable hardshell jackets, ski gloves and walking boots. But, in order for the microporous membrane to perform to its potential when you’re adventuring, exercising or working, you need to keep a few things in mind:

Illustration how the membrane works with water vapour.

The water vapour needs to reach the jacket. Otherwise, it can’t get out.

To ensure that the membrane maintains complete breathability, which is responsible for transporting water vapour molecules through the GORE-TEX® membrane, there has to be a difference in temperature and humidity between the inside and the outside of the garment. This means that the breathability of a jacket with a GORE-TEX® membrane works best in low to mid-range temperatures.

To ensure the long-term functionality of GORE-TEX® products, it is absolutely essential to care for them properly and regularly. With frequent wear, the insides of functional garments inevitably become contaminated with sweat, dirt and sunscreen, all of which can negatively affect the breathability of the fabric. However, if you wash your GORE-TEX® products on a regular basis, both the durability and the breathability of the garment will be significantly improved.

Hardshell clothing is generally worn as part of a layering system and forms the weatherproof outer shell, which is responsible for shielding you from wind and rain. However, to ensure that the fabric is just as breathable as it is waterproof, the rest of your layers have to move water vapour away from the body just as well as your shell does. If you’re wearing anything that lacks moisture-wicking properties under your hard shell, the GORE-TEX® membrane won’t perform to its full potential. This is why outdoor athletes opt for functional underwear and warm mid-layers made of breathable synthetic fabrics. These allow water vapour to travel quickly and unhindered to the outside.

As you’ve probably already gathered, there’s really no way around GORE-TEX®. It’s a staple in the outdoor industry and it seems like it’s here to stay. There are pros and cons to this, especially when you consider the fact that ePTFE is not entirely safe, but we won’t go into that here. If you have any general questions about GORE-TEX®, please do not hesitate to contact us.

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