The influence of the molecular structure of binary block-type styrene-butadiene rubber on dynamic mechanical properties under normal and high-pressure conditions

Through anionic two-stage polymerization, block-type styrene-butadiene rubber (SSBR) with systematically regulable low-temperature loss peaks is successfully prepared. The influence of 1,2-Bd unit in the soft segment of block-type SSBR on mechanical properties, dynamic mechanical properties, and microscopic morphology is studied, while pressure factors are introduced into dynamic mechanical studies. The block-type SSBR with a soft segment containing 21.9 wt% of 1,2-Bd exhibits the highest tensile strength, elongation at break, and tear strength. Under atmospheric pressure, the soft segment 1,2-Bd unit influences the dynamic mechanical properties by altering the chain segment's motion loss capability. As the mass fraction of 1,2-Bd increases from 21.9 to 58.6 wt%, tan δ max increases, the glass transition temperature of the soft segment increases from −59.0 to −18.9°C. Additionally, influenced by thermodynamic compatibility, the microscopic morphology transitions from strong separation to weak separation. Pressure affects dynamic mechanical properties by altering the free volume of the chain segments. Pressure reduces tan δ max , increases T g , and raises the average T g of the soft segment by 11°C. The K value of the linear equation representing the relationship between the soft segment T g and the mass fraction of 1,2-Bd is unaffected by pressure.