Research On Synthesis Of Star-Shaped Solution Polymerized Styrene-Butadiene Rubber Initiated By 1, 1-Diphenylhexyllithium

With the rapid development of automobile industry, high performance tires was demanded. It was reported that 50% of rolling resistance is caused by hysteresis loss of the tread rubber. Balancing wet skid resistance and rolling resistance of tire tread is the development direction of high-performance tires. The hysteresis loss and heat generation can be reduced by modifying the macromolecular chain end. Moreover, the interaction between polymer and fillers and the filler dispersion in the matrix can be improved by this way.1,1-Diphenylhexyllithium(DPHL)was firstly prepared by n-butyllithium and 1,1- diphenylethlene through addition reaction. Then linear-shaped polybutadiene, polyisoprene, polystyrene and styrene-butadene copolymer(SSBR) were synthesized using DPHL as initiator, and finally, SnCl4 was added as coupling agent to react with living polymer chains to prepare star-shaped polymers. Coupling efficiency(E) of SSBR was measured. The effect of polymerization time, structure of the end, amount of SnCl4, coupling reaction temperature, coupling reaction time and molecular weight on E were investigated. Physical properties and mechanical properties of the vulcanizates were measured. The results showed that DPHL was an effective living ionic polymerization initiaor and the coupling efficiency could reach to 74.3% when using the optimal reaction conditions as follows:the molecular weight of 7.0×104, n(Cl-)/n(Li+) of 1.12, polymerization time of 60 minutes, coupling reaction temperature of 60°C, coupling reaction time of more than 30 minutes. The E would be higher when convert the chain end to butadiene. Research of mechanical properties of the vulcanizates showed that:Compared with SSBR initiated by n-butyllithium, SSBR initiated by DPHL appeared excellent physical and mechanical properties, stronger interaction with filler, lower Payne effect, and most importantly, exhibited higher 0°C tanδand lower 60°C tanδ, which means higher wet skid resistance and lower rolling resistance. This modified SSBR can be used as high-performance green energy saving tire tread rubber.