Science on the road to a more colorful tire

Carbon black is a material found in tires that makes the rubber stronger and gives tires their distinctive black color. But a new food waste technology may have you seeing more colorful tires in the future. Professor Katrina Cornish of The Ohio State University has been researching the use of tomato peels and egg shells as a replacement for carbon black.


Carbon black is a material found in tires that makes the rubber stronger and gives tires their distinctive black color.

But a new food-waste technology may have you seeing more colorful tires in the future.

Professor Katrina Cornish of The Ohio State University has been researching the use of tomato peels and eggshells as a replacement for carbon black.

Professor Cornish joins me now via Google Hangout.

So first of all, for most of us who don't pay attention to tires until they run flat, what's a tire made of?

Well, a tire is made of two different sorts of rubber -- synthetic rubber and natural rubber -- and then all sorts of other things, like steel and nylon and various other pieces as well as the metal in your wheel rims.

But the tire itself is black because of the reinforcing filler that creates a lot of the strengths required.

Now, tires don't have the same ingredients, all of them.

So an airplane tire, for example, is 100% natural rubber, whereas your passenger car tire has some synthetic and some natural mixed together all in different parts of the tire.

And so where do the tomato peels and the eggshells come in?

Well, the reinforcing fillers, that is carbon black -- We're using these as replacements for some of the carbon black because we found that microfillers produced from tomato peels and from eggshells are actually, like carbon black, reinforcing fillers.

They add strength.

They don't just dilute the rubber as an extender.

They actually make it stronger in the same way that carbon black does.

And you picked those two partly because of the kind of commercial nature of the excess tomato peels and excess eggshells that apparently exist, not just from my garbage can.

That's correct.

These are produced in very large quantity at food-processing plants, and the amount produced in the states is extremely large.

So for example, we have over 430,000 metric tons of tomato peels produced every year in the U.S., and we have over nearly 600,000 tons of eggshells, and more than half of that is at food-processing plants, where you can go in and collect it very easily.

So I'm not suggesting we go get your breakfast eggshells, so we'll leave those be, for the moment anyway.


And you have, in your lab, the material that's made out of them.

Would that end up influencing how a tire looks?

Would it look a little bit more reddish-brown?

Yes, with the tomato peels, you could, but carbon black is very black, so you'll be looking at, you know, slightly reddish-brown.

But, if you still have carbon black in there, that would be the issue.

However, we have also made these materials with nano-eggshells, so we can do a complete replacement there.

But we're not really suggesting that, because this would be a very expensive tire.

But you can make that one colored.

And then we're also looking at these as partial or full replacements of the silica filler that is used in certain specialty tires as an alternative to carbon black, and those tires, those materials could be colored, too.

We actually made some bright yellow ones last week.

How did the tires with your fillers that include tomato peels and eggshells, the composites -- How do they compare with the tire that I might buy at a store today?

Well, at the moment, I do want to be clear.

No tires have actually been made.

We're making the compounds and testing test specimens, but they actually compare very well and very comparable, because we're using carbon black as our control.

So we're not saying one bio-based filler or waste-derived filler is better than another one.

We're saying, 'How does this stack up against the industry standard?'

One thing that we do get are some interesting shifts in the combinations of properties.

So normally, a reinforcing filler, the more you put in, the stronger it gets, but the stiffer the tire gets, the less elastic it gets in that material until you reach a point of failure, where there's just too much filler.

But we're breaking that paradigm a little bit.

So we might be able to say, 'Okay.

If you want the same strength and you want the same hardness but you'd like to keep some elasticity that you wouldn't normally be able to get, we can keep some of that in for you.'

So those three major properties are a little bit disconnected with our fillers, which hasn't been seen before.

So how would that help a driver?

For example, in a snow tire where you want to have particularly good grip, something like that, you might be able to have an advantage.

Or if you've got a tire that's going over very rough terrain, you need it very strong.

But if it's, like, the pink Jeeps in Sedona or something, you know, you might want to be able to go over your off-road tires where you can really go up the mountainside and need more grip, but you also need the strength, so you could have all the strength you need but still have more squishiness, if you like, so it can hold on to the terrain better.

What happens to most tires?

Do they end up in landfills, and would the filling in your tires decrease that impact in any way?

Well, that's hard to say.

A lot of tires end up in landfills or in giant tire piles.

There's more and more work going on trying to recycle them, you know, so that they get the metal taken out of them, and they end up in asphalt or children's playgrounds.

So there's more and more work in that area.

Our materials wouldn't affect those sorts of destinies.

In terms of degradability of the tire, of course, our fillers -- our tomato peel filler would be somewhat degradable compared to what's in there.

The eggshells wouldn't.

But they are inside the tire, so unless you break up the tire in some way so that they're accessible to the air and to water, they wouldn't be degradable any more than your regular fillers because they just wouldn't be accessible in that way.

All right.

Katrina Cornish from Ohio State University, thanks so much for joining us.

Okay. Thank you very much.

It's been my pleasure.