What is difference between Gore-Tex and rain jackets? vol.1

Gore-Tex and rainwear indicate the same thing to begin with, but Gore-Tex is a waterproof material, or more accurately, a rain jacket made of Gore-Tex material.

In this section, we will explain the Gore-Tex material so that you can understand the Gore-Tex material and the structure of a rain jacket. In particular, vol. 1 will provide basic knowledge of rain jackets.

Gore-Tex is a material, not a rain jacket

Gore-Tex rain jackets are often referred to as "Gore-Tex rain jackets," but Gore-Tex is not a manufacturer of rain jackets. Gore-Tex is a material. It is not wrong to say it is a fabric, but to be precise, it is a piece of fabric. Gore-Tex is like a thin film, also called a membrane. This membrane is impervious to water, so fabrics made of GORE-TEX are waterproof. This waterproof fabric can be used to make rain jackets that can withstand even the harshest rain.

Gore-Tex is a material that is not only used for rain jackets. There are coats and down jackets, bags, shoes, and in the past, tents were also made of Gore-Tex. Therefore, Gore-Tex does not necessarily mean a rain jacket.

Not only waterproof performance, but also other advantages

However, Gore-Tex has properties not found in other waterproof materials.

The most distinctive property is breathability. Basically, waterproof fabrics are made with a membrane or coating, and the membrane or coating is designed to seal the fabric grain, or gap, and keep it waterproof. Because the fabric seals the fabric's seams, it also loses its breathability and moisture permeability (called moisture permeability). Therefore, when wearing a rain jacket, the inside of the jacket becomes damp and stuffy, making it uncomfortable. However, since waterproof property cannot be maintained without sealing the fabric, it was conventionally thought that it was inevitable that the inside of a rain jacket would become stuffy when the jacket is worn.

Gore-Tex material has solved this problem.

Gore-Tex is a waterproof fabric that is also breathable.

Because Gore-Tex is a membrane, it is waterproof without allowing water to pass through. However, as mentioned above, this membrane looks like a thin film, but when it is magnified, it is made of finely intertwined fiber-like material. Although it is a film, there are slight gaps in it. The size of these gaps is 1.4 billion microscopic gaps per square centimeter. Thanks to these gaps, neither water nor moisture can pass through, but water vapor can pass through. It is not breathable, but it does allow moisture to pass through. This is what we call moisture permeability. We have succeeded in combining the contradictory properties of waterproof and moisture permeability. We call this waterproof breathable material. The use of this waterproof breathable material is the difference between an expensive rain jacket and an inexpensive one.

To summarize, Gore-Tex = waterproof breathable material.

Gore-Tex is not the only waterproof breathable material

Despite its excellent properties, Gore-Tex is not the only waterproof and breathable material in the market. There are other materials with the same properties.

For example, a material called SYMPATEX is also waterproof and breathable, and Dermizax is another waterproof and breathable material developed by Toray. There is more. Technically speaking, GORE-TEX is made from a fluoropolymer called ePTFE (which has been replaced by ePE since around 2024), and there are other materials made from polyurethane that are classified as porous PU or non-porous PU. These are also waterproof and breathable materials that combine waterproofness and moisture permeability.

Waterproofness used to be ensured by coating

Traditionally, waterproofness has been ensured by coating. This is because umbrellas are basically coated on the inside to keep them waterproof. Even today, coated rain jackets are still sold. If you remember that the rainwear you used in your childhood was stuffy and difficult to wear, it may have been a rain jacket with this non-breathable coating. The key point is that they can be made inexpensively. However, the coating is also susceptible to deterioration due to direct exposure to moisture, skin oils, rubbing, and other stresses.

The method of ensuring waterproofness by sandwiching the aforementioned membrane between fabrics is sometimes classified as the membrane method, while the method of maintaining waterproofness by coating with a waterproof resin is sometimes classified as the coating method.

Maintenance is important for moisture permeable materials.

There is one important point here. Whether membrane rainwear or coated rain jackets are made of breathable materials, they all have one thing in common: they must be maintained. This is because dirt can inhibit moisture permeability. No matter how high the moisture permeability is claimed in the catalog specifications, it is only the initial performance, and the actual specifications will always be lower. The reason for the lower performance is, of course, that the operating environment differs from the test specifications, but another important factor is that the space for moisture permeability is blocked by dirt and other factors. In the case of our expensive rain jackets with breathability, regular maintenance is required to keep the fabric clean. Of course, water repellency is also important. It is easy to imagine that if water has seeped into the fabric, the breathability is significantly lower. Let's understand that a high-performance rain jacket is also very hard to maintain.