Coolmax, a trademark of Invista, is a brand name for a series of moisture-wicking technical fabrics developed in 1986 by DuPont Textiles and Interiors (now Invista). The fabrics employ specially-engineered polyester fibres to improve "breathability" compared to natural fibres like cotton. 'Wick away' or 'wickaway' is a general term used for fabrics that are engineered to draw moisture away from the skin through capillary action and increased evaporation over a wider surface area.
Coolmax fibres are not round, but are slightly oblong in cross-section with grooves running lengthwise along the threads. They are manufactured in either a tetrachannel or hexachannel style. The series of closely spaced channels creates capillary action that wicks moisture through the core and out to a wider area on the surface of the fabric which increases evaporation.
CoolMax fabric was originally developed for clothing intended for use during extreme physical exertion — sweat can evaporate quickly so the wearer is kept dry. Other useful properties include resistance to fading, shrinking and wrinkling. The fibres are now often woven with other materials like cotton, wool, Spandex and Tencel. As a result, CoolMax is found in a wide variety of garments from mountain climbing gear, to casual sportswear and underwear.