Managing heat and humidity – a question of balance
Constant body temperature has always been of essential importance for all our bodily functions. Since the 1980s it has been the motivation behind different functional systems, which, whilst wider in scope of performance, have been designed to be more and more comfortable to wear.
In order to ‘manage’ humidity i.e. to transfer perspiration in liquid or vapour form away from the body to the air outside, the only solution is to manage heat. When the body is active (movement, sport) it heats up and initiates its own cooling mechanism of perspiration. When a body is warm and the surface of the skin is damp it is essential to protect it from ‘windchill’, undesired cooling caused by moving air. This balancing function has been achieved traditionally by membranes, microscopically stretched, non-porous or bionically active such as in the ski collection from Kjus. Kjus supplies sports and outdoor clothing and is part of the Swiss LK International AG. In its clothing it uses the c-change membrane from Schoeller.
The membrane imitates the way the fir cone system works. When the membrane becomes warmer or more moist (due to the ambient temperature or bodily heat) the polymer structures open and so increasingly permit perspiration – also in liquid form – to pass. However, when the environment becomes cooler, the pores close and provide additional heat insulation, just as required. These are properties that have proven themselves also in complete clothing systems from underwear to outerwear.
Phase-change materials take a different technological approach, making use of a physical phenomenon. In this case it is microscopic capsules incorporated in or on the textiles. Outlast is the leading protagonist of this technology. Outlast calls theses capsules ‘Thermocules’ and they are filled with a substance similar to paraffin to reduce temperature peaks both hot or cold. When heated the filling in the capsules begins to melt, causing energy to be absorbed. Cooling causes the material to stiffen again, releasing the stored heat. In this way phase-change-materials help to maintain a balance. Textiles with these properties are used for outerwear and underwear and additionally for bedding.
However new developments take this a stage further by already embedding the PCM in the fibres. In the case of polyester fibres this is very much state of the art and can be found in the market in the clothing collections of Vanity Fair or Jockey from De Pauli AG, Munich (D). Techtextil will feature the world premiere of developments based on polyamide fibres that are designed for ‘next to skin’ applications, i.e. underwear and sports clothing, with the balancing function of these fibres significantly increasing their comfort factor.
Background picture: Jockey® staycool underwear.Source: Outlast Technologies LLC