A fire-resistant plastic finds its way back to recycling
An additive raised adhesion by about 40%, enabled the top vertical flame rating and was more than 90% removable during washing.
Lightweight materials for electric vehicles face a conflict: improving fire resistance often makes recycling harder. A team at the Korea Research Institute of Chemical Technology, known as KRICT, addressed both properties in one material. Dostonbek Sodik Mavlonov is the study’s first author, and Jin Chul Kim, Ji-Eun Jeong and Young-Jae Jin led the research. The institutional release came from the National Research Council of Science and Technology on Newswise, with no named individual reporter.
Their solution is a self-reinforced composite, meaning that its matrix and reinforcing fibers belong to the same polymer family. Here, both fibers and films use high-density polyethylene, a thermoplastic that softens again when heated. A low-molecular-weight, branched modified-polyolefin additive helps molten film enter fiber gaps and disperses flame-retardant particles without large clumps.
In laboratory tests, the additive increased adhesion between film and fibers by roughly 40%. Even with flame retardant making up 40% of the mass, the material reached UL-94 V-0, the highest rating in the Underwriters Laboratories vertical flammability test: samples extinguish quickly and do not drip flaming material that can ignite objects below. The researchers report that mechanical performance was maintained.
Recycling revealed another difference. Washing removed more than 90% of the new additive, while a comparable commercial formulation retained over 40%, which contaminated recovered plastic. The recycled material had color and strength close to virgin plastic. Fabrication stacks at least five alternating film and fiber layers and presses them at 130 degrees Celsius under 10 bar, about ten times atmospheric pressure.
The conclusion is promising but still open at industrial scale. Laboratory evidence shows that fire resistance, adhesion and polymer recovery can coexist in a self-reinforced composite. It does not prove automotive durability, safety after many cycles or commercial-scale recycling. The team plans repeated-cycle tests, measurements of flame-retardant buildup and validation with companies; those results will determine the real environmental and economic impact.
Key points
- The additive improved adhesion between layers by approximately 40%.
- The composite reached UL-94 V-0 even with 40% flame retardant by mass.
- Washing removed over 90% of the additive, but repeated and industrial tests remain necessary.