Environment

Keeping it cool – scientists achieve room-temp tire recycling

Keeping it cool – scientists a...
Recycling old tires could become much more energy-efficient, plus the recycled rubber would be of higher quality
Recycling old tires could become much more energy-efficient, plus the recycled rubber would be of higher quality
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Recycling old tires could become much more energy-efficient, plus the recycled rubber would be of higher quality
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Recycling old tires could become much more energy-efficient, plus the recycled rubber would be of higher quality

Researchers at Durham University in the United Kingdom have developed an approach to breaking down rubber in materials at room temperature. The chemical process uses catalytic disassembly, eliminating the energy-intensive methods of currently-used tire recycling methods.

In a paper published in the journal Green Chemistry, the Durham researchers explain how the process works and how it could be used to recycle vehicle tires, latex gloves, and other polymer-based items which are manufactured in the millions of tons every year. The long-chain hydrocarbon molecules and unsaturated carbons in these rubbery materials are traditionally very difficult to recycle or reprocess easily; especially vehicle tires.

The traditional method for reprocessing rubber is to drastically change the temperature of the rubber compounds to break them down, either by heating them for milling, or freezing them to fracture them. These are energy-intense and leave a crumb product which is then mixed with new elastomers to produce new material, often with a loss in hardness or malleability.

These losses mean that most recycled rubbers are not re-used for the purpose they were originally formed, but are instead recycled into other products lower down the use chain. This often means that the cost-benefit for recycling is diminished.

The Durham researchers believe that their chemical process may be used to allow the materials to be recycled back into their original use – so a recycled tire could be made into a new tire. Their cross metathesis reaction breaks down rubbery polymers into viscous liquids that can then be reformed without degradation. The process could also be used to create the crumb now commonly produced, but at much lower cost.

The process discovered uses Grubbs' catalysts to break down polybutadiene (PBd) networks at their double bonds via cross-metathesis (CM) reactions to produce readily soluble molecules. As the chains fragment, the material disintegrates into rubber crumb at room temperature. Grubbs' catalysts are easily synthesized and readily-available commercially.

The researchers also discovered that increasing temperature and reaction time improved the breakdown process, also offering a faster way to facilitate rubber compound breakdowns when producing crumb. The resulting oil is low in molecular weight and non-polymers (oligomers), both conducive to easy re-use of the polymers being recycled.

Source: RSC Green Chemistry

6 comments
Jay Finke
Manufactured in the millions of tons every year. no joke, I remember a time when ground up tires were used for fill, for on and off ramps on I 35 in minnesota near Hinckley, this was well over 30 years ago. Tires are a real bad problem and this chemical recycling process sounds too good to be true, let's hope it works !
Charles Barnard
For over a century we have been making long-chain polymers out of hydrocarbons we extract from the planet, and then been unable or economically unwilling to break them back down into shorter chains for reuse. In theory, this is the same cracking procedure used in refining in the first place. This will eventually create a procedure to reuse rather than use increasingly risky extraction methods to provide new feedstock. Finally, we may be able to recycle the same high percentage of plastics which we routinely do for metals like copper, gold, steel, etc. Of course, to work, we need to actually USE the technology, which will require investment in large-scale processing facilities. This probably will not be done unless the government forces it, as it acts against the natural urges of those extracting fossil fuels to extract every possible dollar. We have a method to reduce titanium refining costs by at least 90%, announced by MIT 10 years ago. This could make titanium alloys nearly as inexpensive as aluminum alloys. But no one currently is interested in building a commercial refinery using this technology....
Stephen N Russell
Lisc process alone & save landfills alone, nationwide & in Mexico, China, Russia, India
LakeeshaGobeatcha
I believe it was in AZ about 30 or more years ago when the Governor had some hundred or more miles of highway repaved with blacktop mixed with rubber crumb from old tires. This was done as a test to prove the efficacy of the new process. It worked too well, with the new product outlasting the standard product by at least 10 to 1. Not only that, it gave a much quieter and smoother ride. The Governor wanted to use this new process for all new paving and repaving projects in the state, however, the powerful road construction business put the pressure on and stopped him in his tracks. The only time since then that I've heard of the crumb product being used was here in Las Vegas, NV, not too long ago on a few miles of the local freeway system. It seems that when money is concerned, you CAN stop progress if it hurts the bottom line.
Bruce H. Anderson
I have heard it said that tires have a finite life. No matter if you store them in the shade, drive limited miles, or put all kinds of goo on them, the clock is ticking. So it appears that it is true for some parts of the rubber compound, but not all. And to Jay's point, old tires are a BIG problem. I too hope this is scalable and that the process is energy efficient, economically viable, and environmentally sound.
dsiple
Yay, no endless tire fires! And the steel belting can be recycled, as well.