Multi-Functionalized SSBR & Compound Vulcanizate Performance Characteristics

Increasingly, national countries legislatives are enforced, which are directed towards decreased CO₂ emissions. Among others the steadily expanding automobile sector is committed to improve energy efficiency, e.g. to achieve specific national countries CO₂ emission targets for automobiles. As an example, the EU has set mandatory CO₂ emission targets for new passenger cars of 130 g [CO₂]/km by 2015 and 95 g [CO₂]/km by 2020 (whereas the 2020 target is currently undergoing amendment) [1], and for light commercial vehicles of 175 g [CO₂]/km by 2017, and 147 g [CO₂]/km by 2020 [2].

A tire needs to contribute to automobile fuel efficiency through low tire rolling resistance associated with acceptable to excellent grip, abrasion resistance and noise characteristics. Stated properties, particularly rolling resistance, wet grip and abrasion resistance correlate with each other. For example, the rolling resistance can be improved at the expense of the tire wet grip and/or the abrasion resistance and vice versa. Accordingly a styrene-butadiene copolymer with relatively high styrene concentration exhibits good wet skid resistance along with relatively high rolling resistance. On the contrary, it is very challenging to improve the wet grip properties and the rolling resistance while maintaining a specific abrasion resistance level.

Functionalized SSBR was reported to enhance the interaction of polymer chain ends with silica and/or carbon black leading to a significant decrease of rolling resistance and heat build up in tires, correlating to a reduced vulcanizate hysteretic energy loss, while the wet grip or abrasion resistance are at least not deteriorated [3].

As a result of our developmental work at Styron R&D, novel multi-functionalized polymers are available which enable an improvement of the rolling resistance and wet grip performance property indicators in cured silica and carbon black formulations by up to 40% and 30% respectively, compared with commercially available silica- and carbon black-active Styron functionalized SSBR grades. Additionally the abrasion resistance is maintained at the same level.

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[1]  Regulation (EC) No 443/2009 of the European parliament and of the council of 23. April 2009.

[2]  Regulation (EC) No 510/2011 of the European parliament and of the council of 11. May 2009.

[3]  For a selection of patents on functionalized SSBR from DOW/Styron please see: a) S. K.-H. Thiele, J. Kiesekamp, N. Jantsch, T. Knispel, W.O. Patent No. 2007/047943, Dow Chem. Co.; b) S. K.-H. Thiele, J. Kiesekamp, W.O. Patent No. 2008/076875A1, Dow Chem. Co.; c) S. K.-H. Thiele, , E. Hamann, J. Kiesekamp, W.O. Patent No. 2009/148932, Dow Chem. Co.; d) S. K.-H. Thiele, S. Rulhoff, W.O. Patent No. 2011/079922A1, Styron Europe GmbH; e) S. K.-H. Thiele, S. Knoll, S. Rulhoff, W.O. Patent No. 2011/076377A1, Styron Europe GmbH.