Researchers develop recyclable flame-retardant carbon-fiber-reinforced plastic

By Park Sae-jin Posted : June 9, 2020, 14:18 Updated : June 9, 2020, 14:18

[Courtesy of KIST]

SEOUL -- Researchers have developed a recyclable carbon-fiber-reinforced plastic that is flame retardant. Such material is four times lighter than steel but 10 times stronger, making it ideal for the production of core materials in aerospace, automobile and shipbuilding industries.

The Korea Institute of Science and Technology (KIST) said in a statement on Tuesday that its research team led by professor Jung Yong-chae has developed a recyclable, fire-retardant and smoke suppressing tannic acid-based carbon-fiber-reinforced plastic (CFRP) by mixing epoxy resins based on tannic acid and carbon fiber.

Tannic acid is a specific form of tannin, a type of polyphenol mainly found in unripe fruits and tree leaves. The organic substance adds a distinctive bitter and sour taste to various types of wines and teas.

Conventional CFRP products include materials from halogens, a chemical group in the periodic table including chlorine and bromine, to provide flame-retardant characteristics. However, CFRP products emit toxic fumes when combusted due to halogen materials.

To create a fire-retardant plastic that emits less smoke, researchers added tannic acid, bio-epoxy resin, a polymeric matrix, and carbon fiber. Tannic acid extracted from plants worked as an adhesive to hold the polymeric matrix and carbon fiber together. Researchers said that tannic acid becomes char when combusted, blocks an inflow of oxygen and stops the spread of a fire.

The tannic acid-based CFRP can be recycled using supercritical deionized water with no additives to create carbon spheres from the degradation of the epoxy matrix and clean carbon fibers. A carbon sphere is an allotrope of carbon in which a molecule consists of carbon atoms connected by single and double bonds to create a closed or partially closed mesh shaped like a sphere.

Such a byproduct created during the recycling of CFRP can be used in the production of products in various industries. Carbon spheres are basically electrical insulators but when they are crystalized with alkali metals, the compound can become a superconductor.

The research was published in the latest issue of Composites Part B: Engineering, a scientific journal.
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