This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Korean researchers have developed a recyclable flame-retardant composite that overcomes a fundamental limitation of conventional flame-retardant composites, which cannot be recycled once cured, while maintaining excellent flame resistance. A research team led by Dr.
Young-Jae Jin at the Korea Research Institute of Chemical Technology (KRICT) has developed a self-reinforced composite (SRC) fabrication technology that simultaneously achieves improved processability, flame retardancy and recyclability simply by adding a low-cost, low-molecular-weight polyolefin additive. The findings are published in the journal Composites Part B: Engineering. The technology is expected to enable the use of lightweight, recyclable components in next-generation mobility applications such as electric vehicles, which have traditionally relied on metals or nonrecyclable thermoset fiber-reinforced composites.
Fiber-reinforced composites, a type of thermoset composite material, have been widely used in products that require high flame resistance, including automotive components, electronic circuit boards and electrical outlets. Because their shape becomes permanently fixed after curing, they can maintain their structural integrity even in high-temperature environments such as fires. However, once cured, these materials cannot be melted again, even when heated, and therefore must be landfilled or incinerated at high temperatures.
With the growing emphasis on carbon neutrality, regulations on and replacement of "nonrecyclable materials" have become inevitable, creating an urgent need for composite materials that are reprocessable while also providing flame retardancy and processability. To address this challenge, the research team developed a self-reinforced composite by stacking layers of high-density polyethylene (HDPE) fibers and films, which can be reprocessed when heated. The researchers added a small amount of a low-cost, low-molecular-weight polyolefin additive to the intermediate film, enabling it to perform three functions simultaneously.
The additive makes the material more flowable so that the film and fibers adhere tightly without gaps; helps flame-retardant particles disperse uniformly without agglomerating; and can be effectively removed by washing during recycling. Interlayer adhesion is a key factor determining the durability and safety of composite components. With the new additive, adhesion between the film and fibers improved by approximately 40% compared with the material without the additive.
In addition, although incorporating as much as 40 wt% flame retardant would normally cause a substantial decline in strength and flexibility, the composite achieved the highest flame-retardant rating, UL 94 V-0 (the highest rating under the UL 94 vertical burning test established by Underwriters Laboratories (UL); materials rated V-0 rapidly self-extinguish after ignition and do not produce flaming drips that ignite combustible materials below), without compromising its mechanical properties. Meanwhile, materials containing a conventional commercial additive retain more than 40% of the additive during recycling, resulting in a significant deterioration in material properties. In contrast, more than 90% of the additive used by the research team could be removed, enabling the recovery of high-purity recycled material with color and strength comparable to those of virgin plastic.
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