High-tech Belgian monofilaments producer Luxilon Industries NV has developed an award winning cooling monofilament yarn which can cause the surface of fabrics to cool by up to 3.7°C. Luxicool was developed in conjunction with French knitted fabrics producer Sofileta SAS and was awarded an Avantex Innovation Prize in the Comfort + Function category for ‘Luxicool Performing Yarn in Sofileta Cooling Fabrics.'

Luxicool is a patented and trade mark registered cooling monofilament yarn whose cooling efficiency is said to be generated by a dual effect - the excellent thermal conductivity of the polymer itself and the accelerated evaporation of moisture due to the specific polymer construction. Luxicool yarn is a monofilament with natural colour and is available in 50 denier (55 dtex), 70 denier (77 dtex) and 100 denier (110 dtex) counts.

 "Luxicool is a light elastic monofilament which can be used in all standard textile technologies such as weaving, knitting and braiding. It is probably the only filament that evaporates and cools and really cools," says Luxilon's Techno-Commercial Manager Herbert De Breuck.

De Breuck says that Luxicool is the ideal cooling filament in sportswear, work wear, military wear, protective clothing, medical bandages, sports bandages; burns wound treatments, hospital linen and shoe fabrics.

Combining for optimal cooling

Luxilon recommends that Luxicool is used in combination with other yarns such as multifilament yarns made from polyamide or polyester. According to Luxilon the combined effect will be to improve comfort and transport moisture to the Luxicool for improved evaporation and cooling.

"The ideal way to use Luxicool is in twisted yarns and in this respect we are cooperating with a French twisting company, Massebeuf Textiles, which has developed a whole range of twisted Luxicool products," says Herbert De Breuck.

Luxicool applications

According to Luxilon, the main areas of application for Luxicool are temperature control in sports applications and medical applications which include fever control, improved comfort for hospital beds for long term patients, improved comfort during long term use of orthopaedic bandages and improved comfort during burns wound treatment. Other anticipated areas of application are improved comfort for work wear and military clothing. 3D knitted spacer fabrics are expected to be an important medium for delivering Luxicool benefits in functional underwear.

Due to its particular polymer structure, Luxilon advises that it is important not to exceed temperatures of 120°C during the processing or use of Luxicool either in yarn or fabric format. Special surface treatments such as dyeing and coating are not recommended as these might influence the cooling effect of the polymer. Using pre-dyed yarns in combination with Luxicool is a possible colouring solution.

Test results  

Herbert De Breuck stresses that Luxicool has been tested intensively before launching and tests have been carried out on a dynamic sweating torso, which are said to have shown remarkable results. "By using Luxicool yarn in a fabric, a cooling effect up to 3.7°C is possible. This effect is there as long as the activity continues. Once the activity stops a quick recovery occurs," explains De Breuck.

"Tested at different institutes and with different methods and technologies, each time it was proven Luxicool performs extremely well as a cooling material. By optimizing the structure of the fabric and using the right combination of twisted yarns we can even improve it," De Breuck adds. "The cooling is a synergistic effect of thermo-conductivity, specific heat of the material and evaporation of moisture or transpiration."

According to Luxilon, two of the most important tests carried out were:

• ‘Physiological measurement with the sweating torso' at EMPA, St Gallen, Switzerland
• ‘Physiological testing of thermo-conductivity on a mannequin' at Centexbel, Verviers, Belgium

Results of the tests are available from Luxilon.

Cooling knitted fabrics

Sofileta is a specialist knitting company which has created a range of fabrics based on the Luxicool technology called Sofileta Cooling Fabrics. According to Sofileta, the fact that Luxicool is a non-dyeable continuous monofilament was the main difficulty to overcome before it could be integrated into a fashion fabric with particular comfort properties and without affecting the cooling properties.

Luxicool yarn was twisted with other hydrophilic yarns, which is said to have further enhanced its moisture management properties. The resultant range of yarns in different colours and counts was then able to be used to make a ‘comfortable' fabric with a soft handle and good aesthetic appearance, whilst retaining the moisture management and cooling properties of the Luxicool yarn.

Using its experience of manufacturing specialist sports apparel fabrics, Sofileta selected the most appropriate knitting structures in order to achieve the greatest cooling effect and the best moisture management properties.

In double sided patterned Sofileta Cooling Fabrics, two different fibres appear on each side. The fabrics are designed in such a way that the inner layer, which will be next to the skin in the resultant garment, contains the Luxicool yarn so that the cooling effect is immediately felt by the skin

Special patterns with differently structured surfaces on each side are said to improve perspiration transport through the fabric, the so called ‘push-pull effect'. This is another approach to enhance the cooling and moisture management properties of Sofileta Cooling Fabrics.

Sofileta says that knitted structures in different forms have been tested by multiple customers, amongst them a top 20 ATP tennis player, a major professional cycling team and a special police forces unit. The company says that five important customers have recently validated and approved Luxicool in its Sofileta Cooling Fabrics for their next collections.

The effect of Sofileta Cooling Fabrics is due to specific properties of the Luxicool polymer and appropriate fabric structure. The cooling effect is immediate and is boosted in presence of moisture. The repetition of the cooling effect is infinite for the lifetime of the fabric and does not degrade by laundering.

Importance of cooperation

Luxilon is keen to emphasise that the key to the success of Luxicool is the good cooperation between several partners. De Breuck explains: "The whole chain from extrusion to finished fabric is included, so a good monitoring of the behaviour of Luxicool was possible. Each step has its own specific characteristics which might influence the cooling effect."

Besides the close cooperation with Massebeuf Textiles for twisted yarns, Luxilon also teamed up with French technical textiles company Sofileta and UK knitted spacer fabric producer Baltex to develop a whole range of brand new and high performing fabrics for multiple markets including sportswear, workwear, military wear and medical products.

"Due to the close cooperation between the industrial partners, supported by famous research institutes, a good performing and well studied product is ready to convince the market," Herbert De Breuck says.

"Luxicool is performing better and longer than other existing cooling products on the market. Besides the cooling effect, Luxicool cannot be washed out like PCM materials and is wash resistant. The cooling is also permanent whereas the effect of phase change materials disappears," adds De Breuck.