Could It Become a Savior from the Extreme Heat? How Teijin Frontier Developed the Innovative Material "COOLSHELL CARAT" that Reduces Sweat Stickiness and Provides Contact Cooling

With the recent impact of global warming, the ability to develop cooling-effect fibers has become a key differentiator from competitors. Especially in the sports market, there is a demand for clothing that supports comfortable performance even in the harsh summer heat.
 
The material "COOLSHELL CARAT" developed by Teijin Frontier Co, Ltd. is expected to be a groundbreaking material that breaks conventional wisdom. It successfully combines contact cooling functionality and reduces the uncomfortable stickiness of sweat, which has been considered difficult to achieve until now.
 
To learn more, I spoke with Nobuaki Ogata, the development director of the company, about the background of "COOLSHELL CARAT" and the technology that made it possible.

Drawbacks of Contact Cooling Materials

Teijin Frontier has been developing remarkable functional fibers such as super hollow cross-section yarns "Octa" and the polyester and nylon blended "Mixel NP". In recent years, they have also started developing fibers that suppress microplastic emissions with eco-friendliness in mind.
 
Amidst this, recognizing the increasing demand for sports clothing with cooling functions due to warming, they began to readdress the issue of sweat management.
 
"Natural materials have been used for a long time. Cotton, rayon, and silk inherently contain moisture, which provides a cool sensation.
 
"Additionally, synthetic fibers that hold moisture within their structure are said to possess contact cooling properties. However, these fibers have low sweat diffusion and tend to become sticky, which is a drawback."
 
Previous fibers were considered to have conflicting functions of contact cooling and quick-drying properties. For contact cooling, the fabric must closely adhere to the skin, which is not suitable for sweat.

To prevent sweat stickiness, it was necessary to create a structure on the inside with uneven surfaces to reduce the contact area with the skin, leading to a new development effort.

Developed Functional Fibers

To achieve a balance between contact cooling and quick-drying, specialized functional fibers were needed: "WAVERON®" and "TRIPLEDRY® CARAT®."
 
The first developed was "WAVERON®", a fiber with a quadrilateral flat cross-section. By incorporating titanium oxide, the "FD WAVERON®" that exhibits cooling properties was created and has been adopted by major apparel manufacturers for several years.
 
According to Ogata, "FD WAVERON®" was designed to promote contact cooling, but there were requests from athletes to suppress the feeling of sweat stickiness while wearing it.

While searching for solutions, "TRIPLEDRY® CARAT®" was developed through a different flow. This structure reduces sweat return by appropriately arranging moisture-absorbing yarns and water-repellent yarns.

However, the crimped yarn used for the water-repellent yarn tends to feel warm, which is counter to the cooling function.

Therefore, the company has started developing materials that combine these two elements. The key was to develop the water-repellent yarn of "FD WAVERON®." By cleverly arranging the newly developed water-repellent yarn with the conventional moisture-absorbing yarn, it was expected to provide a cooling sensation on the skin while also eliminating stickiness.
 
While explaining this in words may seem simple, were there any challenges in the development of the "FD WAVERON®" water-repellent yarn?
 
"The ability to effectively repel water is crucial, and for that, the presence of a crimp in the yarn is key. However, 'WAVERON®' is a non-crimp yarn.
 
"Theoretically, it was difficult to incorporate a water-repellent function into a structure that is inherently not suited for repelling water, so we struggled with the precise calculations of the yarn's form and the amount of water-repellent agent needed, in addition to ensuring the stability of its function."

After overcoming numerous obstacles, the groundbreaking "COOLSHELL CARAT" was completed. When viewed under an electron microscope or optical microscope, its astonishing structure is revealed.
 
"If you look at the skin side, you will see that the water-repellent yarn and the moisture-absorbing yarn are alternately arranged. Moreover, this is strictly about the skin side; the outer layer consists of a two-layer structure utilizing a finely woven and flat material called 'DELTA®.'

"Typically, adopting such a structure would make the fabric itself unstable, causing irregularities and making it prone to snags. Nevertheless, in order to achieve both a cooling sensation and water repellence, we chose this audacious structure."
 
As Ogata mentions, "COOLSHELL CARAT" can be considered a crystallization of Teijin Frontier's technology. Thus, there should be no doubt regarding its performance. Its moisture absorption and water repellency are clearly demonstrated in experimental videos.

"Regarding cooling performance, we have verified it according to the recognized JIS method in the industry. We conducted experiments by exposing a sample to heated thermal plates raised to +20 degrees Celsius and achieved a result of a contact cooling Q-max of 0.2 W/cm2 (⊿Ｔ＝20℃) or more.

"Generally, a value of 0.2 W/cm2 or higher is accepted as evidence of a contact cooling function, meaning its effectiveness is sufficient. The breathability that prevents stuffiness and stickiness is also impeccable.
 
"Moreover, the sweat management function shares the same structure as CARAT, indicating it has a comparable quick-drying capacity. The integration of water-repellent yarn provides the admirable feature of drying quickly after washing.
 
"Furthermore, considering environmental factors, it is free of PFAS (perfluoroalkyl and polyfluoroalkyl substances), and the yarn used is entirely composed of 100% recycled materials."

With such remarkable performance, what future developments are anticipated for "COOLSHELL CARAT"?
 
"We aim to sell 100,000 meters by 2025 and 1,000,000 meters by 2028. Until now, the demand for functions like contact cooling was primarily from the Asian market. However, due to the recent impact of global warming, we have also begun receiving inquiries from Europe. As such, I believe these figures are not just hopeful forecasts but achievable targets."
 
Ogata remarks that "COOLSHELL CARAT" possesses performance suitable for both domestic and international markets. Therefore, it is being considered for uses beyond its initial application as sportswear.
 
"Initially, the focus was on sports use, but considering its functionality, it can also be suitable for corporate uniforms and innerwear, aiming for a wide range of applications such as heatstroke prevention items.
 
"However, the material still tends to give off a sporty vibe, so we're considering switching the outer material from 'DELTA®' to something else or improving the texture of the plastic feel using our technology."
 
The company has already been holding exhibitions every few months, diligently working on creating materials that meet market demands through interactions with customers. Ogata also shared that "COOLSHELL CARAT" will continue to evolve.
 
This summer, "COOLSHELL CARAT" is expected to attract significant attention.