Asahi Kasei launches Lastan flame-retardant nonwoven for EV battery packs

Asahi Kasei (Tokyo, Japan) has introduced a novel material solution for enhanced electric vehicle (EV) battery safety. A flame-retardant and highly flexible nonwoven fabric, Lastan is well suited for use in top covers, busbar protection sleeves and other applications within the EV battery pack to protect against thermal runaway. As an oxidized acrylic fiber, Lastan can also be laminated into a composite surface layer.

Although EVs are becoming more common worldwide, battery safety is still a major concern for many car users. In this context, there is increasing demand for materials in EV battery cover applications that offer optimal resistance against flames and particle blasts, as well as good electrical insulation properties. While mineral-based materials are generally used as protection against thermal runaway at present, such materials tend to be heavy and brittle. According to Asahi Kasei, these stiff materials are difficult to adapt to complex shapes, making processability an issue for automotive OEMs.

Lastan is a non-mineral flame-resistant fabric made by air baking an acrylic fiber at 200-300°C. It is characterized by high flame resistance and good electrical insulation, which are further improved by a coating process that also augments abrasion resistance. This enables the material to provide effective protection against particle bombardment from venting gas, according to the company. Lastan has been used as a material for failure prevention and safety in various for many years. 

When exposed to a 1300°C flame for 1 minute, Asahi Kasei reports that the temperature on the opposite side of Lastan remains below 400°C and no holes form in the material. While a “limiting oxygen index” (LOI) value of 27 or higher is generally considered to indicate flame retardance, this material has an LOI value of 50 or higher. In UL94 flame retardance testing, Lastan has obtained the highest rating of 5VA. 

In addition to its high flame resistance, Lastan offers resistance to high-pressure impact by 200–500 μm particles. It also provides electrical insulating capacity of up to 3.5 kV at a thickness of 1 mm. Lastan features high processability, and is highly flexible while maintaining its performance characteristics in sheets as thin as 0.8 mm. This makes it easily processed with ordinary tools.

Lastan has currently been integrated into production in Japan. Asahi Kasei is also considering production in the U.S. and other countries in the future.