UNDERSTANDING THE INFLUENCE OF OLIGOMERIC RESINS ON TRACTION AND ROLLING RESISTANCE OF SILICA-REINFORCED TIRE TREADS

This study concerns the silica reinforcement of styrene butadiene rubber compounds for passenger car tire treads, with the objective of gaining greater insight into the beneficial effects of oligomeric resins. The major tire performance factors predicted are rolling resistance and (wet) skid resistance measured on a laboratory scale. Three types of resins were tested: a polyterpene, a terpene-phenolic, and a pure vinyl-aromatic hydrocarbon resin, at various concentrations, namely, 2, 4, and 6 parts per hundred of rubber (phr). Laboratory scale dynamic mechanical analysis (DMA), Mooney viscosity, cure meter, and tensile and hardness tests were used to assess the behavior of these resins in the rubber and to characterize the processibility of the compounds. The DMA shows that the resins and rubber compounds are partially compatible for the low resin quantities used. The tan delta loss factor versus temperature was used as an indication for wet skid and rolling resistance. The shift to a higher temperature in the tan delta peak, due to the contribution of the tan delta peak shift of the resins, is the reason for improved wet skid performance. A maximum improvement of about 35% in the wet skid region (0 degrees C-30 degrees C) is found. The improved tan delta at 60 degrees C, indicative for rolling resistance, accounts for reduced interaction between filler particles. This is also confirmed by a decrease in the Payne effect. A maximum improvement of about 15% is found in the rolling resistance temperature range, dependent on the particular choice of the resin.