Although carbon fiber can be repaired and recycled to a certain extent, it's typically just discarded once it's damaged. According to a recent study, however, a new type of the material can be easily fixed or reused through the simple application of heat.
Currently, most carbon fiber products are made out of what are technically known as carbon fiber reinforced polymers (CFRPs). There are in turn two types of CFRPs: thermoset and thermoplastic.
The more commonly used thermosets incorporate an epoxy polymer, which permanently hardens once cured – this makes the material strong, but quite difficult to subsequently rework. By contrast, thermoplastics utilize a softer polymer glue that can be melted down as needed. Unfortunately, though, they're not as strong or stiff as thermoset CFRPs.
With these limitations in mind, a University of Washington team led by Asst. Prof. Aniruddh Vashisth looked to a newer group of carbon fiber materials, called carbon fiber reinforced vitrimers (vCFRPs) – they are claimed to combine the best qualities of thermosets and thermoplastics.
Like the thermoset polymers from which they're derived, the vitrimer plastics in vCFRPs initially form strong chemical links, resulting in a strong and stiff material. However, when the vitrimers are heated – utilizing either traditional or radio frequency heat sources – those links are released, allowing any cracks or other defects to self-heal. Once the vitrimers cool, the links reform and the material regains its strength.
In this way, it's reportedly possible to repair damaged or degraded vCFRPs multiple times, and to eventually break them down for recycling.
"These materials can translate the linear life cycle of plastics to a circular one, which would be a great step towards sustainability," says Prof. Nikhil Koratkar.
A paper on the research was recently published in the journal Carbon.
Source: University of Washington
