Bringing Innovation to the Surface: Functionalized Silicas for Improved Natural Rubber Truck Tire Vulcanizates

The technical benefits of compounding precipitated silica with silane in passenger car and light truck tire tread compounds containing synthetic styrene butadiene (SBR) and butadiene (BR) polymers are well documented. In particular, this approach has enabled a significant reduction in rolling resistance (up to 30 percent), which can be realized as a six percent improvement in passenger car and light truck fuel efficiency. In response to new fuel efficiency legislation affecting medium and heavy duty trucks, there is a great deal of interest in realizing similar gains in a segment which relies heavily upon natural rubber based compounds to achieve an appropriate balance in wear, tear strength and dynamic mechanical properties. The complete replacement of carbon-based fillers using conventional in-situ silica/silane mixing in natural rubber has proved challenging for several reasons. Natural rubber contains up to six percent by weight of impurities such as dirt, ash, sugars, proteins and metal ions, all of which have some affinity toward the silica surface and can inhibit coupling with the silane. Furthermore, the mixing/dump temperatures frequently utilized to drive the silane coupling reaction to completion in-situ has been shown to degrade natural rubber networks. The Agilon™ performance silica technology platform from PPG Industries pre-reacts a coupling agent and a dispersant with the silica surface, allowing compounders to overcome these problems and achieve improved truck tire vulcanizate properties. Here we discuss the performance of Agilon™ performance silicas in a natural rubber based heavy duty truck tread compound.