Car tyres should not only be more economical and safe, but simultaneously more environmentally friendly. To this end, Continental is developing an alternative rubber material from dandelion rubber. What does the new technology offer?
Tyres are made primarily from crude oil. But not exclusively: tyres, in particular Winter tyres, can already be manufactured with high proportions of renewable raw materials. In the case of Winter tyres, the natural material content can even be as much as 30 percent. Alongside the artificial raw materials such as synthetic rubber, industrially produced soot and various additives, which also come from the chemicals factory, natural rubber and rapeseed oil (as a softening agent) are used in particular. However, due to the costs of transport from regions near the equator, natural rubber is very expensive. Cheaper alternatives are sought– and this is not a recent development. Already, back in the 1940s, the Soviets were searching for a replacement and found it in the root of the Russian dandelion (lat. Taraxacum).
Taraxa gum, the new tyre rubber
Natural rubber can be acquired from its sap in the same way as from the rubber tree. Scientists at the Fraunhofer Institute for Molecular Biology and Applied Ecology in Münster have managed, together with chemists and engineers from Continental, to develop a process for the production of tyre rubber. The logical name: Taraxa gum.
On the path from garden weed to rubber supplier, the unassuming Caucasian dandelion had, in some respects, to be optimised and adjusted for the tyre industry: mainly through classic cultivation it was possible to produce plants with enlarged roots and thus increase the yield of rubber from the sap contained therein. In addition, the enlarged root, as is the case for example with potatoes, allows for efficient mechanical harvesting.
Best grip thanks to natural rubber
Work is being done to this end. The tread compound is still the best keep secret of a tyre. It consists primarily of natural and synthetic rubber, as well as fillers such as soot or silica, oils and sulphur. Through vulcanisation (the heating of the mixture to approx.120–160 °C) the macromolecules of both rubber types form long-chain polymers, which are interconnected by sulphur bonds – producing rubber. Through the intelligent mixture of the individual components, the properties of the tyre rubber can be considerably influenced.
The advantage of this often more expensive natural rubber over many synthetic rubbers is this: it remains considerably more flexible at low temperatures. Thus, especially in Winter tyres, a high proportion of the expensive rubber will ensure the best grip on snow and ice. A cheaper material, acquired from the dandelion root, could in future guarantee the performance of such tyres at an affordable level, or perhaps even improve the performance level.
On the market from 2020 at the earliest
It is no secret: Contis motivation for this future investment is of course the cheaper production costs of the tyres. Essentially, the need for expensive crude oil products and conventional natural rubber will be reduced, and because the unassuming dandelion can be grown in unused fields clsoe to the factory, even in inhospitable regions of Europe, the CO2 emissions are reduced by shorter overall transport routes.
How far along is the development? The first harvests of rubber made in Germany have already been collected, and the first test tyres baked. The alternative tyre material is currently being trialled in Winter tyres. The first Conti WinterContact TS 850 Ps with Taraxa gum compound are currently being put to the test on Nordic trails. However, whether the dandelion tyres can bite down as powerfully on snow and ice as their conventional colleagues must yet be determined. According to Conti statements, a market launch can be expected in 2020 at the earliest.
Garden herb tyres as an agricultural promoter
The rubber produced from the sap of the Russian dandelion should correspond to that from the rubber tree both in terms of quality and consistency and can therefore be used for the manufacture of tyres and other rubber articles without serious process modifications. Dandelion as a source of rubber could therefore provide new impetus for Europe's agricultural sector: while a classic rubber tree can only be used to extract sap after around seven years of growth, the dandelion can be harvested just a year after cultivation. An appealing aspect for cultivators, who could react comparatively quickly and flexibly to demand.
What does a car tyre consist of?
The treads:Contact is established with the road with an impressed profile. The rubber compound in the treads, together with the profile, define the most important properties of the tyre, such as dry and wet grip, grip on snow and ice, roll resistance and wear. Here the dandelion rubber, Taraxa gum, could be used.
The belt cover layer:Consists of nylon cord or even Kevlar and further reinforces the tread. This makes the tyre suitable for use at speed and ensures a more even load distribution on the tread.
The steel belt:Consists of several rubber coated steel mesh parts. It ensures stability and thus is the only way to enable flat tyre construction.
Textile cord inlays:Together with the steel belt and belt cover layer, they form the carcass - the load-bearing frame of the tyre.
Interior layer or inner liner:The particularly airtight rubber compound on the inside of the tyre protects against gradual loss of pressure.
The side wall of the tyre:Here the rubber compound differs significantly from that on the tread. Its properties and construction primarily influence primarily the roll resistance, the responsiveness when steering and the ride comfort. In addition, it protects the tyre from damage, for example in the event of unintentional contact with the curb.
The core profile:Together with the apex filler this forms part of the bead and serves to reinforce the carcass and also influences both the tyre deformation under lateral force and the deflection comfort.
The steel core:A stable ring made from steel wire, surrounded by the carcass. It ensures that the tyre sits securely on the rim.
Bead reinforcers:Reinforcements in the side wall of the tyre, which provide stability and precision in tyres intended for sporty driving.
Conclusion
Back to the roots
In order to cover the ever increasing demand for tyres and to compensate for the competitive disadvantages of longer transport routes compared to those of Asian suppliers, European rubber manufacturers are looking for alternatives. With the dandelion rubber, Taraxa gum, Conti is on the ecologically correct path. For this is the only option whereby cultivation can take place in Europe.
Author
Thiemo Fleck
Photo
Continental
Date
24 June 2015
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