Carbon fiber composites may be light and strong, but their fire resistance has always been a problem,media New Atlas reported. But now, South Korean scientists have discovered that a plant-derived substance keeps them from burning and making it easier to recycle. In the past, halogens were added to carbon fiber composites in order to make carbon fiber composites flammable. However, the use of toxic substances when incinerated materials are recycled is eventually banned worldwide. During the incineration process, the epoxy resin in the composite material is burned, leaving only carbon fiber fragments.
Led by Dr. Yong-Chae Jung, researchers at the Korea Institute of Science and Technology (KIST) recently tried to replace halogens with tannin acid. The tannin acid is a rich natural polyphenol produced by plants. When added to the epoxy resin, the acid improves the adhesive capacity of the resin to the carbon fiber. But more importantly, tannins are carbonized when exposed to the flame — creating a carbonized layer on the carbon fiber surface that prevents oxygen from entering the material. As a result, the composite material is both hard and flammable.
In addition, as long as the material is placed in supercritical fluid state water, it can be completely recycled — meaning that the temperature and pressure of the liquid are kept above a specific critical level. Composites dissolve “for ten minutes” after immersion, allowing more than 99% of the fibers and resins to be recycled.
What’s more, recycled resins can be used to produce carbon quantum dots, which are now used in objects such as LEDs and organic solar cells.
“We have created a composite material with an expanded range of applications that offers significant improvements in flame retardant, mechanical rigidity and recyclability compared to conventional carbon fiber-reinforced plastics. Dr. Yong-Chae Jung said. “These improved traits are significant because they determine the scope of application of the composite material. “
The paper on the study was recently published in the journal Composites Part B: Engineering.