Sweaty clothes during intense exercise can lower your body temperature and reduce your performance. This increases the risk of hypothermia, especially in cold environments, which emphasizes the need for technical fabrics that wick moisture away quickly. For example, Coolmax fibers made from polyester wick sweat away from the skin through capillary action to keep you cool, and are also cold and bacteria resistant, making them ideal for a variety of outdoor activities.
When you work out vigorously and sweat profusely, your clothes can get wet and become less functional. The clammy feeling can be uncomfortable, and the weight of the sweat can hinder an athlete’s performance. This doesn’t just reduce performance; in the long run, it can also affect your ability to regulate your body temperature. The more sweat you produce, the easier it is for your body to cool down as it rapidly draws heat away from the surface of your skin. This is especially true in low-temperature environments, where not wearing the right clothing can increase the body’s energy expenditure and increase fatigue during exercise.
In addition, on cold and windy days, sweat can steal heat from your body as it cools, causing hypothermia in extreme cases. Running in the wind in damp clothes can cause up to 240 times more heat loss than running in dry clothes. To solve this problem, sportswear must be able to not only adapt to the temperature, but also evaporate moisture quickly to help regulate body temperature. Therefore, there is a need for functional materials that not only absorb moisture, but also evaporate it quickly to the outside, and several have been developed. A representative example is Coolmax, developed by DuPont.
Coolmax is made of polyester, a material that does not retain moisture well. Natural fibers such as cotton, which have a lot of specific chemical structures that like to bind with water molecules, absorb moisture well and don”t dry out when wet. Polyester fibers, on the other hand, have very few of these specific chemical structures, so they don’t bind to water molecules as easily, so they don’t absorb water as well and stay dry. But if polyester fibers don’t absorb water well, it’s hard for them to wick it away, so how is it that Coolmax fabric made of polyester is able to wick sweat away from the skin so quickly?
The secret has to do with the cross-section of the yarn. Chemical fibers, like polyester, are made from hot molten raw materials that are cooled and hardened as the liquid exits through microscopic pores and forms into threads. The initial yarn formed is called the ‘yarn’ and the tiny holes through which it exits are called ‘spinnerets’. The cross-sectional shape of the yarn is determined by the shape of the spinnerets. The cross-section of the Coolmax yarn that emerges from the cross-shaped spinneret is the same as the shape of the spinneret, so the sides of the yarn are grooved in all directions. Fabrics woven with these yarns have microscopic pores, which increases the surface area exposed to moisture in the air compared to fabrics woven with yarns with a normal circular cross-section. Moisture that comes into contact with the fibers is drawn out of the fabric through the microscopic pores by capillary action.
Capillarity is a phenomenon in which the surface of a liquid rises to the top of the tube when a narrow, long tube is placed in a liquid, such as the absorption of water by plant roots or sponges, or alcohol rising to the wick of an alcohol lamp. In the case of Coolmax fibers, the adhesion of the water molecules to the walls of the micropores causes the edge of the water to rise up the wall, and the cohesion between the water molecules causes the entire water surface to rise to the height of the edge water molecules. The continuous interaction of these two forces allows all the sweat on the skin to escape the fiber and evaporate.
Because Coolmax fibers have such a low water content, they can evaporate moisture much faster than cotton fibers, and even drenched clothing can be put back on after a single twist, wring and shake. These properties are very practical for those who spend a lot of time outdoors. In particular, Coolmax fibers are useful for athletes, hikers, and campers because they wick away sweat while remaining warm in extreme conditions. Due to its chemical nature, Coolmax fiber is also resistant to pests and has excellent antibacterial properties, making it easy to care for, which is why it is widely used in T-shirts and other sportswear, and can be blended freely with cotton yarns, expanding its use to underwear and socks.
The properties of a fiber depend not only on the chemical composition itself, but also on the cross-sectional shape and thickness of the threads and the weaving method. Previously, when developing apparel materials, researchers focused only on the chemical structure, which is microscopic and one-dimensional, but in recent years, there has been an active movement to discover new functional fibers by appropriately changing and combining the remaining fiber elements. Given this trend, it’s safe to assume that we will continue to see more creative materials like Coolmax fibers in the future.
In the end, functional textiles are evolving to meet the needs of modern people who seek comfort in their daily lives, and they are expected to find applications in a variety of industries, not only in everyday wear and sportswear. At a time when advanced material technology is making a huge difference in our lives, functional textiles will continue to develop further and play an important role in improving the quality of human life.
