Silica Morphology and Functionality: Addressing Winter Tire Performance

Tire manufacturers attempt to maximize microhysteretic properties in studless winter tires for optimum traction.  Recently there has been a renewed interest in further improving the fuel efficiency in winter tires without sacrificing other cold-weather properties.  In addition there has been an interest in obtaining the traction of studded tires without the associated noise and road surface damage.  Market research shows there is a growing demand for winter tires driven by increased legislation and governments/tire manufacturers pushing for greater public awareness of winter driving safety.  The background science of winter tire traction is complex, but can be predicted in the laboratory using Dynamic Mechanical Analysis (DMA). There are three primary modes of traction in winter weather: dry, ice, and snow. The types of winter hazards, the underlying science for each and the DMA tests employed to predict performance are reviewed.   The elastomer ratio (sSBR, BR and NR), silica surface area and loading, and silica to carbon black ratio in the tread formulation had a significant impact on the predicted winter tire performance.  While high-BR content provides favorable predicted winter tire performance higher Tg polymers like NR and sSBR are added to improve warm weather dry and wet traction as well as to improve rolling resistance.  In addition, a higher loading of lower surface area silica (i.e. Hi-Sil™ EZ90G-D) was also shown to provide an overall improved predicted winter tire performance.