Researchers at the Korea Research Institute of Chemical Technology who conducted the study. From left: Bae Hyeong-eun, Jeong Hae-min, Jin Yeong-jae (senior researchers), Kim Jin-cheol, Jeong Hyo-cheol (principal researchers), Jeong Ji-eun (senior researcher) and Park Yeong-il (principal researcher). [Korea Research Institute of Chemical Technology]
Researchers at the Korea Research Institute of Chemical Technology who conducted the study. From left: Bae Hyeong-eun, Jeong Hae-min, Jin Yeong-jae (senior researchers), Kim Jin-cheol, Jeong Hyo-cheol (principal researchers), Jeong Ji-eun (senior researcher) and Park Yeong-il (principal researcher). [Korea Research Institute of Chemical Technology]

South Korean researchers have developed a technology that makes flame-retardant composite materials used in electric vehicles recyclable — using just a single additive.

A research team led by Kim Jin-cheol, Jeong Ji-eun and Jin Yeong-jae at the Korea Research Institute of Chemical Technology announced Tuesday that they had developed a manufacturing technology for "self-reinforced composite materials." The technology simultaneously achieves processability, flame retardancy and recyclability by adding only a small amount of low-cost, low-molecular-weight polyolefin additive.

Fiber-reinforced composite materials — a type of thermosetting composite — have long been the material of choice for products that must resist fire, such as automotive parts, electronic circuit boards and electrical outlets. Because their shape is permanently fixed, they maintain structural integrity and remain safe even in high-temperature environments such as fires.

Once hardened, however, these materials cannot be melted down no matter how much heat is applied, leaving landfill disposal or high-temperature incineration as the only options.

As carbon neutrality has become a global priority, regulations on non-recyclable materials have grown increasingly unavoidable and substitutes are being sought. Developing "recycling-friendly" composite materials that can be remolded while also meeting flame-retardancy and processing requirements has emerged as a shared challenge for industry.

The research team developed a self-reinforced composite material by layering fibers and films made of high-density polyethylene (HDPE), a thermoplastic that can be reprocessed when heated.

A small amount of low-cost, low-molecular-weight polyolefin additive was incorporated into the intermediate film layer, enabling it to perform three functions at once.

The self-reinforced composite material containing the additive developed by the institute (right) achieved the highest flame-retardancy rating of V-0 without any degradation in mechanical properties. [Korea Research Institute of Chemical Technology]
The self-reinforced composite material containing the additive developed by the institute (right) achieved the highest flame-retardancy rating of V-0 without any degradation in mechanical properties. [Korea Research Institute of Chemical Technology]

Adhesion between layers is a key factor in the durability and safety of composite parts. Adding the new additive improved bonding between the film and fiber layers by about 40 percent compared with conventional materials. At the same time, while high flame-retardant loadings of 40 percent typically cause a significant drop in strength and flexibility, the material achieved the top flame-retardancy rating of V-0 with no loss in mechanical properties.

When materials containing conventional commercial additives are recycled, more than 40 percent of the additive remains, sharply degrading material quality. With the team's additive, more than 90 percent is removed during recycling, yielding high-purity recycled feedstock whose color and strength match those of virgin plastic.

The team plans to conduct additional flame-retardancy tests for industrial application and follow-up research to ensure that flame retardants do not accumulate over repeated recycling cycles. The researchers also intend to collaborate with prospective industry partners on property evaluation and pilot studies to accelerate the commercialization of next-generation structural composite materials for mobility applications.

"This research solved the long-standing challenges of processability and recyclability in flame-retardant composite materials using a single, inexpensive additive," Kim said. "It will contribute to improved energy efficiency and reduced carbon emissions through lightweighting in electric vehicles, urban air mobility and electronics."

The findings were published in the international journal Composites Part B.


nbgkoo@heraldcorp.com