Influence of oligomeric resins on traction and rolling resistance of silica tire treads

This study concerns the silica-reinforcement of synthetic rubber compounds for passenger tire treads with the objective to gain insight into the beneficial effects of oligomeric resins, derived from natural and synthetic monomers, on the major tire performance factors: Rolling Resistance and (Wet) Skid Resistance. This manuscript highlights the relationship between the performances of various oligomeric resins in different concentrations: 2, 4 and 6 phr, on the dynamic mechanical behavior of the silica reinforced passenger car tire tread compounds. Three types of resins were tested: a polyterpene, a terpene-phenolic and a pure vinyl-aromatic hydrocarbon resin. Dynamic Mechanical Analysis (DMA) was used, in addition to Mooney viscosity, cure meter, tensile and hardness tests 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 compatible at the resin quantities used. The tan δ loss angle versus temperature was used as an indication for wet skid and rolling resistance. The shift to a higher temperature in the tan δ peak belonging to the glass transition (Tg) of the rubber phase, due to the contribution of the higher Tg of the resins, is the reason for improved wet skid performance. A maximum improvement of ca. 35 % in the wet skid region (0 - 30 °C) is found. The improved tan δ at 60 °C, indicative for rolling resistance, accounts for reduced interaction between filler-particles. This is also confirmed by a decrease in Payne effect. A maximum improvement of ca. 15 % is found in the rolling resistance temperature range, dependent on the particular choice of the resin.