Rheological property of 1,2-polybutadiene grafted styrene-butadiene copolymer

The 1,2-polybutadiene grafted styrene-butadiene copolymer(1,2-PBR-g-SB) with different content of SB was synthesized.The rheological property of the grafted copolymers was studied by double capillary rheometer and compared with that of linear 1,2-polybutadiene(1,2-PBR).The results showed that the grafted SB could decrease the numbe-average molecular weight and increase the weight-average molecular weight and increase the weight of 1,2-PBR,and broaden the molecular weight distribution.Before and after grafted,1,2-PBR both had high content vinyl(over 80%),and the apparent viscosity of 1,2-PBR decreased with temperature rised from 80 ℃ to 120 ℃.After grafted,the viscous flow activation energy of 1,2-PBR increased evidently,but it reduced gradually,and its sensitivity of viscosity to temperature weakened with increasing the grafted SB.However,the effect of grafted SB on the sensitivity of viscosity to shearing of 1,2-PBR was more complex,before and after grafted,the apparent viscosity of 1,2-PBR decreased with increasing shear rate from 150 s-1 to 3 000 s-1.The non-Newtonian index of the linear 1,2-PBR and 1,2-PBR-g-SB with SB mass fraction 5% decreased obviously,but with SB mass fraction 1% increased,which was more close to Newtonian fluid,while with SB mass fraction 7% remained almost no changes.At the temperature of 80 ℃,100 ℃,and the same shear rate,the apparent viscosity of three kinds of 1,2-PBR-g-SB decreased first and then increased with increasing the grafted SB,and the 1,2-PBR-g-SB with SB mass fraction 7% had the highest viscosity.