Lanxess Shows Off Latest SR Know-How
The consistent further development of synthetic rubber has resulted in a significant improvement in the overall performance of vehicle tyres. Synthetic rubber manufacturer Lanxess AG highlighted recent progress in this area at the recent 4th Intelligent Tire Technology Congress, held on October 21 and 22 in Wiesbaden, Germany.
Newly developed production processes have paved the way for the use of solution styrene-butadiene rubbers (S-SBR), reports Lanxess. Trials performed at the company’s test laboratories and in customer trials have shown that, with these new tyre tread elastomers, it is possible to simultaneously raise wet grip and rolling resistance – formerly totally contradictory properties – to a completely new level.
“Current debate on intelligent tyres is focused primarily on the progress being made in the field of sensor technology,” says Christoph Kalla, head of Marketing in Lanxess’s Performance Butadiene Rubbers business unit. “We are delighted with this latest development, because it shows just how much modern tyre production can profit from the use of state-of-the-art special-purpose rubbers from Lanxess.” For example, says Lanxess, the latest tyre pressure monitoring systems directly highlight the potential of its current butyl and halobutyl rubber grades.
The difference between standard and high-end products often involves making difficult modifications to the elastomer molecules. This is something that today can only be mastered by research-intensive premium providers in the rubber sector, commented Lanxess’ Norbert Steinhauser, who is currently working on the further development of styrene-butadiene rubber grades that are produced by the solution process via so-called “anionic polymerisation”. This technology results in particularly low-branched rubber molecules, noted for their comparatively narrow molecular weight distribution, which rubber experts associate with good abrasion resistance and rolling resistance. It has already been possible to modify these molecules in many ways via their chemically active terminal groups. They can, for example, be joined to one another to improve their processing properties or be provided with special chemical “anchor points” at the ends to allow the rubber to interact better with fillers, thereby improving the rolling resistance of the tyre without impairing grip on wet roads.
Lanxess reports now taking this concept a step further by introducing “intelligent” solution SBR rubber grades that have “anchor points” not just at the ends of the molecules but along their entire length. These enable the elastomer to interact with other constituents of the rubber. Laboratory trials showed that such S-SBR rubbers have precisely the desired properties that are associated in practice with improved wet grip (high tan δ value at 0 °C) and, simultaneously, reduced rolling resistance (low tan δ at 60 °C). With “conventional” rubber types, it was impossible to increase one value without lowering the other. The abrasion level is also very low with these new rubber grades. Furthermore, the positive effect is seen even when the microstructure of the rubber is varied by making normal changes to the polymerisation conditions.
“The effects we have been seeing in the laboratory are in some cases quite dramatic,” said Steinhauser. “And in initial practical trials at some of our customers, they have also yielded improved tire performance.” This has, says Lanxess, given tyre developers a completely new tool to work with: Now, for the first time, rolling resistance and wet grip can both be significantly optimised at the same time.
“This latest example shows what can still be achieved with modern tyre raw materials,” Kaid concluded. “It also demonstrates just how much innovation potential there still is in the material, even nearly a hundred years after the discovery of the first synthetic rubber in the laboratories of our predecessors in Leverkusen.”