The idiom ‘reduce, reuse, recycle’ has been a part of our lives for decades. Three little words have gone on to save countless tonnes of rubbish from landfill, and remain an important cornerstone of a sustainable future.
Unfortunately, not all materials are created equally, with some being more difficult to recycle than others. Certain plastics, ceramics and rubber are particularly difficult to dispose of in a sustainable way. Vehicle tyres, for example, represent a significant volume of discarded waste in Australia and around the world. Industry analysts estimate there are well over one billion cars currently in use globally, whose worn and damaged tyres end up in landfills to decompose, releasing toxic substances into the soil. These landfills are occasionally the source of massive tyre fires, creating acrid black smoke and treacherous firefighting conditions.
A team of researchers led by Associate Professor Justin Chalker of Flinders University, set about creating rubber that can be repaired, or otherwise more easily recycled. This has great potential to reduce the environmental impact of tyres.
By running computational chemistry simulations on the NCI supercomputer, researchers discovered a new type of rubber that is made from sulfur, canola oil and dicyclopentadiene, all of which are industrial byproducts and are therefore inexpensive and readily available. By introducing an amine catalyst, a self-repair reaction can be triggered in the rubber. Under ideal conditions, this repair takes just minutes and can be performed at room temperature.
This same reaction also means the rubber can be used as a latent adhesive, where it bonds to the surface of another piece of rubber when the amine catalyst is applied, i.e. the rubber is not ‘sticky’ until the catalyst is applied. This adhesive is also resistant to water and corrosion.
These findings offer potential solutions to reducing tyre waste, by making torn or damaged rubber much easier to repair. The same process can be used to bond two layers of polymer together to produce ‘rubber bricks’ or other innovative materials.
Fundamental studies on the mechanisms of rubber repair were performed by Associate Professor Amir Karton, who used the computational capacity of NCI as part of the research process. He says:
“Computational chemistry is a branch of chemistry that uses sophisticated computer simulations to study the structures and properties of molecules and materials. In this work we used quantum chemical theories together with the awesome computational power of the NCI supercomputer to reveal a novel reaction mechanism underlying the rapid polymerization of the sulfur subunits.”
In cases where traditional chemistry may be impractical, expensive or dangerous, the ability to perform comprehensive simulations offers researchers a compelling alternative, one that is only realised with cutting edge high-performance computers, such as those available at NCI.
The underlying chemistry of these materials has a wide potential in recycling, next-generation adhesives and additive manufacturing. A/Prof Karton adds that the novel reaction mechanism “revealed a key role of the pyridine solvent, and will help optimizing reaction conditions for similar processes in the future.”
‘Chemically induced repair, adhesion, and recycling of polymers made by inverse vulcanization’ (May 2020) by SJ Tonkin, CT Gibson, JA Campbell, DA Lewis, A Karton, T Hasell and JM Chalker in Chemical Science (The Royal Society of Chemistry) DOI: 10.1039/D0SC00855A https://doi.org/10.1039/D0SC00855A