Spacer fabric used in cooling ballistics vest
21st May 2012, Switzerland
Engineers at EMPA, the Swiss research and development organisation, have developed a bullet proof vest with built in ‘air conditioning’ incorporating a novel warp knitted spacer fabric with cooling properties.
The smart protective vest, developed in conjunction with industrial partners has an integrated cooling system based on Coolpad technology, originally designed for use in cooling garments for medical applications. The vests could be worn by police under their uniform shirts.
“Bullet-proof vests made of Kevlar, hold off bullets but are also impenetrable for water vapour. Thus police personnel who must wear such gear under their uniforms sweat profusely when the weather is warm, a situation that can negatively affect the physical performance of police officers on duty,” EMPA explains.
Tested by police force
According to the Swiss organisation, comparative measurements show that the new vest is significantly lighter and also cools much better than systems currently on the market. In practical use too, the vest is said to have proven its worth as staff of the Zürich City police force tested the vest over several warm summer days and gave the new innovation the thumbs up.
The Coolpads built into the vest are filled with water, which is allowed to evaporate through the membrane, cooling down its surroundings. A mini fan blows air though the fabric spacer behind the pad, providing further cooling.
“Integrating such an A/C into a garment proved to be quite tricky. It required a novel fabric spacer, which was stable under pressure yet also flexible and soft to the touch, and which offered very little resistance to air flow,” EMPA says.
A suitable spacer was developed together with Swiss knitted textiles manufacturer Eschler and as there were no fans on the market, which were small enough to be built into the vest, EMPA engineers designed a miniaturized version themselves.
“Two units including batteries and control electronics now provide the cooling air circulation in the vest. Similarly, the cool pads used till then proved unsatisfactory; since in the protective vest they were mechanically quite stressed they frequently leaked water. A new technique for welding the ultra-thin pad membranes using diode lasers proved to be much more reliable than the conventional method, with the seam remaining soft and flexible,” EMPA adds.
In addition the EMPA specialists were able to increase the evaporation rate and therefore the cooling ability.
Portable filling station
But that wasn't all. In order to simplify refilling the cool pads with water they developed a portable filling station that can be attached to the vest with a quick-release fastener. During the same ‘pit stop’, the mini fans can be exchanged for those with freshly charged batteries. Then the vest is ready once again for three to four hours of duty.
The first small series of the novel under-uniform protective vest will be produced in the near future by project partner Unico Swiss Tex GmbH. EMPA says that the smart cooling technology is however, also suitable for protective suits worn over normal clothing, uniform jackets, camouflage suits and even for rucksacks and developments along these lines are already in progress.
EMPA is an interdisciplinary research and services institution for material sciences and technology development. Its research and development activities are oriented to meeting the requirements of industry and the needs of society and link together applications-oriented research and the practical implementation of new ideas, science and industry, and science and society.
Author: Billy Hunter