What is Coolmax, a fiber that wicks water like a sponge?

Learn about coolmax, a fiber that wicks water like a sponge.

 

When you work out intensely and sweat profusely, your clothes can get wet and become less functional. The clammy feeling can be uncomfortable, and the weight of sweat can hinder an athlete’s performance. Also, on cold and windy days, sweat can steal heat from the body as it cools, causing hypothermia in extreme cases. In fact, walking in the wind in damp clothes can cause up to 240 times more heat loss than walking in dry clothes. Therefore, there is a need for functional materials that not only absorb moisture but also dissipate it quickly to the outside, and several have been developed. A representative is Coolmax, developed by DuPont.
Coolmax is made from a polyester-based 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 to get it out, so how do Coolmax fibers made of polyester wick sweat away from the skin?
The secret has to do with the cross-section of the threads. Chemical fibers, such as 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 regular 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. Coolmax fibers are also highly resistant to pests due to the nature of the chemical fiber, and are also antibacterial and easy to care for, so they are widely used in T-shirts and other sportswear, and can be freely blended with cotton yarns, expanding the range of applications 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 is safe to assume that we will continue to see creative materials like Coolmax fibers in the future.