Ever since nanomaterials made their first tentative steps into commercial markets, the early targets were in sporting goods. There is a pretty good catalogue of the different nanomaterials and the various sporting good products that they have been used for in a paper published in the Center for Knowledge Management of Nanoscience and Technology’s (CKMNT) from which an excerpt is provided here.
The CKMNT report was compiled over three years ago and what is conspicuously absent from its list of nanomaterials for sporting goods is graphene. Carbon nanotubes are there as well as carbon nanofibers for bicycle frames—an application I had a brief foray into seven years ago when I tried to discern whether there was any appreciable benefit to using carbon nanofibers than just run-of-the-mill fillers in the composite. But graphene just a few years back didn’t apparently make a blip on the radar.
That has all changed, of course, with graphene finding high-profile applications in tennis racquets and skis, both of which are produced by Head. However, I was more intrigued by the recent application of graphene in cycling since I am an avid cyclist myself.
The application that has gotten a lot of press is the adoption of graphene by venerable Italian cycling tire manufacturer Vittoria when it launched graphene-enabled tire dubbed G+ or Graphene Plus. You can see a promotional video below, but the main advantages of the graphene-enabled tires are supposed to be lighter weight, greater strength and durability. Of course, every tire is supposed to provide good grip and low rolling resistance and this new series of tires claims to tick those boxes as well.
My question was whether graphene could really offer much benefit over conventional reinforcing fillers like carbon black, or were we just looking at a bit of marketing and extra price per tire. So, I asked an industry expert in using graphene with different compounds, who asked to remain anonymous, if much benefit could be derived from using graphene in an application like this.
Vittoria has made it known that they are using a graphene platelet material for their tires. My source explained rubber compounding has so many variables that the kind of graphene platelet they are using would depend on the elastomer system, other parts of the filler system, protection system, process aids, curing package.
He added that as important as the specifications of the graphene are how they are processing the material is equally as important. Conventional reinforcing fillers such as carbon black are usually compounded into the raw rubber in mixers prior to vulcanization. Graphene, he explained, could be added into the product through a similar approach. However there are other routes to introducing graphene into the rubber matrix, which he was not at liberty to discuss.
The aims of modifying tire rubber formulations have traditionally been aimed at improving the so-called "tire triangle" of properties. This triad includes: Low rolling resistance, Abrasion resistance and Wet-traction control.
While graphene has been thought to improve these above properties, my source concedes that no matter what reinforcing fillers are used it is usually very difficult to obtain improvement to all three properties of the tire triangle simultaneously, there is usually a trade-off in performance between these properties.
My source also points out that carbon nanotubes have long been expected to deliver the same type of improvements as graphene to tire performance but have never managed to gain a market foothold.
In the UK-based Cycling Weekly, the question of graphene in tires was given a lengthy discussion in which they interviewed one of Vittoria’s competitors, Continental.
“In the past we did some trials with graphene in the casing and tread of our tyres,” said Christian Wurmbäck, head of product development bicycle tires at Continental in the interview with Cycling Weekly. “However, although the directionality of the compound brought some benefits to the casing, the development of our Carbon Black compounds [which are said to use carbon nano particles] is at a higher level, so there was no need to jump back on graphene.”
It would seem the jury is still out on how much of a difference can make on improving your bicycle tires. I may just have to go and do a test, if I can get someone to send me a couple for testing purposes.