res are carbon black and silica.The use of lower levels of filler and larger sized particles result inbetter rolling resistance. Carbon black is predominantly used in tires,but the use of silica has become a primary alternative to improverolling resistance. When silica is used to improve rolling resistance,it is traditionally used with a silane coupling agent, which is arubber chemical that helps in bonding the silica to the polymer.
The final component in a tire compound for improving rolling resistanceis the cure system. This is a combination of rubber chemicals that,when heated together with the polymer and filler, form insoluble crosslinks, tying everything together into a solid, elastic rubber tirecompound. The cross links are generally derived from sulfur, and themore crosslinks there are the better the rolling resistance will be.
The number of sulfur atoms contained in the crosslink also impactsrolling resistance, with 1 or 2 sulfur atoms being better than 8 atoms.
All these materials now have to be mixed together. Many factors impactrolling resistance during the mixing process, e.g., the order of addingthe ingredients, the mixing temperature and mixing time. All areoptimized to help finely disperse the filler into the polymer, whichsignificantly improves rolling resistance.
In addition, how the tire is manufactured and how the materials areprocessed can affect rolling resistance. Determining the best way tocure a tire (time and temperature) or how to mix the compounds canenable improvements in the physical properties and chemistry of thecompounds in the tire.
Understanding these relationships and controlling them is important to improving rolling resistance.
Skurich is the Lead Engineer, Sport Performance Tires, for Goodyear Tire &Rubber Co.
