Environmentally-friendly means of synthesising graphene have been introduced but production is still largely time-consuming, solvent-intensive and energy demanding. As a solution to this issue, upcycling of rubber waste has been suggested, providing a means to convert low-value waste that would otherwise have been thrown away into high-value carbon nanomaterials for use as reinforcing additives.
Graphene has attracted much attention from scientists around the world, aiming to utilize the material’s superior mechanical properties, remarkable electronic properties and high thermal conductivity in practical applications.
As an example, graphene and graphene oxide derivatives can be used to strengthen cement paste and reduce the consumption of energy and water in its production.
Despite these advantages, however, current conventional production processes for graphene (e.g. mechanical or chemical exfoliation, chemical vapour deposition, chemical oxidation etc.) are expensive, time-consuming, solvent-intensive, energy demanding and more often than not, detrimental to the environmental.
Assoc. Prof. Dr. Shaifulazuar Rozali of University of Malaya’s Department of Mechanical Engineering had been inspired to find new methods of producing graphene that are cheap, beneficial for the environment and capable of utilizing waste products.
He had found potential in utilizing microwaves to convert waste into high-value materials such as nanocarbon and its nanocomposite. “The fast-heating capability of microwave has inspired me to solve other environmental problems by converting plastic waste into fuel,” Dr. Shaifulazuar says.
Following this motive, Dr. Shaifulazuar and his team of researchers had developed an environmentally-safe method of producing new types of graphene for practical applications.
“We have successfully synthesized a type of graphene that can be dispersed in various types of solvents such as water, ethylene glycol, methanol, ethanol and 1-hexanol with high stability and remarkable thermal conductivity,” Dr. Shaifulazuar says about his and his research team’s findings. This new graphene type is produced via grafting citric acid and xylitol polymers onto the graphitic structure, a method that has proven to be both cost-effective and environmentally-safe.
“This success encouraged me to explore other processes to produce nanocarbon at low cost and at the same time could solve environmental problems” Dr. Shaifulazuar says.
Dr. Shaifulazuar’s study into the microwave method was motivated by another study that had developed a method of producing recycling rubber waste into usable graphene via flash Joule heating (FJH).
This method uses an electric current to form high-quality turbostratic flash graphene (tFG) and is compatible with waste rubber feedstocks (e.g. rubber tires etc.) as well as being faster and less expensive than conventional methods.
FJH method provides a rapid and inexpensive means of reusing and recycling rubber waste that otherwise would have been dumped into landfills or burnt.
By further developing these new methods of graphene synthesis, the industry will be able to utilize plastic and rubber waste to produce high-value graphene or carbon nanomaterials for a wide variety of different applications, resulting in lighter and stronger materials at lower costs.
References
Advincula, P.A., Luong, D.X., Chen, W., Raghuraman, S., Shahsavari, R., Tour, J.M. (2021) Flash graphene from rubber waste. Carbon, 178 (2021) 649-656.
https://doi.org/10.1016/j.carbon.2021.03.020
Shazali, S.S., Rozali, S., Ahmad Amiri, Zubir, M.N.M, Sabri, M.F.M, Zabri, M.Z. (2018) Evaluation on stability and thermophysical performances of covalently functionalized graphene nanoplatelets with xylitol and citric acid. Materials Chemistry and Physics, 212 (2018) 363-371.