Tyres are made up vulcanised rubber - rubber combined with sulphur to improve its overall strength and durability. But as vulcanised rubber does not melt, it is difficult to reform and reuse old tyres. The only way to deal with them is dump them in a landfill, a process that releases heavy metals and other pollutants and risks starting dirty, long-burning fires.
Now, David Isaac and colleagues at Swansea University, UK, have shown that spinning ground-up tyres, called rubber 'crumb', inside a chamber filled with ionised oxygen gas plasma makes the crumbs adhesive and allows them to gel better with new rubber.
'It makes the surface of the crumb much better at sticking onto new rubber. Without treatment, the interface between the old pieces and new rubber is very weak', said Isaac, adding that the treated rubber particles can then be added to fresh non-vulcanised rubber to make new tyres.
According to Isaac, laboratory tests have also shown that tyre rubber recycled in this way has similar tensile strength and other mechanical properties to completely new material.
'The plasma treatment appears to create reactive oxygen species - small, highly reactive molecules - on the surface of the rubber by opening up carbon bonds. This reactive surface adheres well to fresh rubber. But it will not stay that way forever, so we have to add it to new rubber straight away. In the long term, wet hope to find a way to make the plasma treatment last longer', New Scientist quoted him as saying.
The Swansea team have now formed a commercial partnership in order to develop the new process commercially and interest tyre makers in the technology.