Viscoelastic and friction characteristics of polydiene, and butadiene–styrene copolymer tread compounds with application to tire dynamics

An experimental study of the linear viscoelastic and friction properties of passenger tire tread compounds containing realistic black and oil contents and several different types of elastomers including cis‐polyisoprene, cis‐polybutadiene, emulsion polymerized polybutadiene, and three emulsion polymerized butadiene—styrene copolymers (SBR's) has been carried out. E′ (ω) and tan δ were determined as a function of frequency and temperature. At any specific frequency and temperature, tan δ was an increasing function of Tg or a decreasing function of T − Tg. When the tan δ–frequency data were plotted at the same T − Tg, all of the treads based upon emulsion‐polymerized butadiene polymers yielded nearly the same curve. Wet coefficients of friction of the tread compounds correlated with both tan δ and T − Tg supporting the idea that lubricated friction is largely due to hysteresis. The correlation among the butadiene—styrene polymers was much better than with the natural rubber, which exhibits a lower tan δ and a higher wet coefficient of friction than an SBR of the same Tg. The experimental results are used to investigate the heat buildup and skid properties of tires containing these tread compounds.