Kelheim Fibres, a leading producer of specialty viscose fibers based in Germany, recently announced it has completed testing of its new viscose infrared-reflecting (IR-reflecting) fiber. The company began working on the fiber roughly two years ago after a textile customer sought a specific IR-reflecting additive integrated in a viscose fiber for a special application, according to Dr. Daniela Bauer of Kelheim Fibres’ R&D team. “Kelheim Fibres was very fascinated from the IR-reflecting topic and decided to develop an IR-reflecting fiber by themselves for other applications,” she adds.

Kelheim tested the incorporation of mineral IR-reflecting particles in several spinning trials in recent months. The company tested various levels of the particles inside the fiber’s core, preserving the fiber’s inherent properties, rather than adding them as a topical finish using additives based on titanium oxide or other metal-based compounds. Dr. Bauer explains that the main benefit of incorporating the IR-reflecting particles in the fiber’s core is that the properties of the viscose are preserved, such as moisture management, softness and skin-friendliness. Also, the IR-reflecting effect cannot be washed out.

Because of these benefits, Dr. Bauer also claims viscose fibers are ideal for the IR-reflecting treatment compared to other natural or synthetic fibers. “It is also possible to regulate the effect by different dosing of the additive in the fiber from low to high,” she says.

According to Kelheim, trials have shown that the new fiber delivers a level of IR-activity that could be proven in measurements of the Total Solar Reflectance Value (TSR). Visible light is reflected by 90%-95%, while in the near infrared range, a reflectance of up to 90% is reached, depending on the wavelength spectrum. The company says this demonstrates a clear benefit in the reflectance of direct sunlight, whereby the fiber can provide a cooling effect by protecting the body from outside radiation. The fibers can also be used in warming applications, where thermal radiation released from the body is reflected by the IR-reflecting particles back to the body, reducing the cooling effect and keeping the body warm.

The new fiber can be used both for textile and nonwoven applications. “We can imagine applications as interlinings in textiles, or as a nonwoven layer as insulating device in buildings. But these are only examples. We believe there are more possibilities in the field of nonwovens and highly interested in developing a nonwoven together with a customer,” Dr. Bauer says.

Dr. Bauer adds that the level of loading the particles can be altered depending on the requirements of the final product. Kelheim is currently producing the fiber on a commercial production line and is looking to collaborate with an end-use nonwoven customer to develop a nonwoven.