More than three billion tyres were sold worldwide last year and this is projected to reach nearly four billion by 2024. Recycling used tyres poses significant challenges but McMaster University in Canada has developed a method which could redress this problem.
‘The chemistry of the tyre is very complex and does not lend itself to degradation – for good reason,’ says Michael Brook, a professor in the Department of Chemistry & Chemical Biology at McMaster. ‘The properties that make tyres so durable and stable on the road also make them exceptionally difficult to break down and recycle.’
The technique for curing tyres dates back to 1850 and involves combining sulphur with natural rubber. This creates bridges between the natural polymers and transforms the mixture from fluid to rubber. Brook explains that his team is working on a process that tackles the sulphur-to-sulphur bond, breaking down the polymeric oils.
As a result, the rubber dissolves leaving material with a structure comparable to fishing net. ‘We have found a way to cut all the horizontal lines so instead of having a net, you now have a large number of ropes, which can be isolated and reprocessed much more easily,’ says Brook, who leads the project.
The McMaster team is confident that the breakthrough has the potential to make recycling tyres a lot easier and less costly. The new method has limitations, though, because it remains too expensive to be used on an industrial scale. The chemist concludes: ‘We’re working on it, but this is the first major step.’
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