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| Pirelli's "Smartube" is a TPU based innertube. |
This post is more of a "book report" on that White Paper, but if you want to read the entire thing, you can download the PDF file from this page.
I will only hit the highlights and things that impressed me. then I want to comment on the findings of that paper and how I think it fits into today's bicycling world.
The first impression I got from this paper was that traditional, "butyl" tubes are not rubber at all. I think if you asked most riders and even bicycle techs, they would be surprised to find this is the case. The paper says that butyl tubes are a combination of "isobutylene and isoprene". (Note- emphasis is mine) So what is that?
According to "Wikipedia", (I know.....not the greatest source, but bear with me) isobutylene is:
"Isobutylene is a hydrocarbon with the formula (CH₃)₂C=CH₂. It is a four-carbon branched alkene, one of the four isomers of butylene. It is a colorless flammable gas, and is of considerable industrial value"
And for "isoprene": (From ScienceDirect Projects)
"Isoprene (2-methyl-1,3-butadiene) is the smallest terpene unit. It is a colorless, volatile liquid with a boiling point of 34 °C. Although isoprene is produced by many plants, it is also a by-product of the thermal cracking of oil and a side product of ethylene production."
Umm......eeeew! But, butyl tubes are the standard of the industry and they do what they do rather well. I think it is important to know what those actually are, because, as I stated earlier, I bet most people would guess that inner tubes are rubber. That they are a synthetic concoction now makes more sense as some inner tubes feel really plasticky, and slick, which their make-up would give them, I see now.
The next tube type, Latex, is rubber. And it has better characteristics than butyl tubes do, but for air retention. So, that's why they are not a big deal, because, as many of us mechanics know, people don't know bicycle tires need air pressure maintenance, and many think that they shouldn't have to do that. 
I ran TPU tubes in my Raleigh last year with good success.
Imagine a world where latex tubes were all you could get! No one would want a bicycle except the nerdiest-nerds.
So, while latex tubes are cool and all, they are not really all that practical, although the White Paper kind of glosses over that fact. The next tube type seems poised for dominance though, and that type is the TPU based tube. These are best known now as "Tubolito" tubes, since they were the first well-marketed TPU type tubes I am aware of. I reviewed a set here last year. (Standard Disclaimer)
But what is "TPU"? Check out this site for details, but it is another chemically based concoction used widely throughout our current society. You could also say "eeeew!" here, but the big difference is that butyl tubes are very difficult to recycle and TPU is not hard to recycle. Plus, there are efforts to make TPU-type plastics from plant based materials, so there is hope that this might actually be a way towards a better-for-the-Earth tube in the future. An example of this is already in the cycling market in the form of biodegradable water bottles.
The obvious advantages of TPU tubes is not debatable, but their costs to buy are, and that will put these sorts of tubes on the back-burner for many cyclists. However; with the future efforts for a more earth-friendly world, I can see where TPU tubes might end up becoming a bigger deal in the near future. especially if they can be derived from plant-based materials.
4 comments:
Thanks for doing the leg-work on this, my base assumption was the complete opposite of what you have found - 'rubber' inner tubes easy to recycle, TPU tubes much harder. That might be a useful marketing angle for companies to push.
It proves the old adage around the word ass-u-me !
Matt
@MuddyMatt - Butyl tubes can be "up-cycled", of course. I've seen belts, bags, and other things made from them. But when I made an effort to try to get butyl tubes recycled I found that it was not easy. The only place that I could find that would take them in the past (for free plus our shipping cost) was Quality Bicycle Products and I believe they were sending them on to be up-cycled into other products, but I may be wrong on that point. I also do not think they are providing that service anymore, but someone else might know more than I.
Automobile tire recyclers will take them, but you have to pay them to take them away, which in the case of the non-profit I work for, this is not feasible. And automobile tire recyclers aren't just everywhere. So, I should say that butyl tubes theoretically CAN be recycled, but it is very difficult to do.
Greets GT, The good old days, Rema patches by 100s.
Personally I find butyl tubes to be the perfect patching material for punctures in butyl tubes. And in a pinch they make a good temporary fix for a side wall cut, within reason also. Cut the patch to whatever size needed, prep both surfaces, then spread a nice even thin layer of contact cement to both surfaces and allow to dry to the touch, Then patch, making sure the entire surface of both is perfectly stuck together, no wrinkles or bubbles. If there is any residual glue around the outer edge of the patch throw on a bit of bathroom tissue to prevent unwanted sticking to other bits. And there it is, a perfect permanent waterproof patch. The other advantage of this over regular tire patch kits is they tend to sometimes let go over time and are not very resilient and tend to pucker when aired up whereas a butyl patch will expand along with the tube and allow the tube to retain its normal shape. Plus butyl tube also makes good shim stock or surface protection under certain circumstances ....
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