Flow of carbon black loaded styrene‐butadiene (SBR)‐cis‐polybutadiene blends through capillary dies—influence of mixing and the location of carbon black

Abstract

Abstract The flow behavior of carbon black loaded styrene‐butadiene (SBR)‐cis‐polybutadiene (BR) is investigated as a function of mixing and the location of carbon black. The blends consist of an 80:20 weight ratio of SBR and BR with the incorporation of 20 phr carbon black via three different schemes to control the location of carbon black in the individual rubber phases. These are: (A) free black mixing of the three components, (B) mixing of SBR‐black masterbatch with BR, and (C) mixing of BR‐black masterbatch with SBR. Dynamic Mechanical Analysis (DMA) was used to characterize carbon black distribution. The damping characteristics indicate that when carbon black is masterbatched into either one of the rubbers, it continues to remain incorporated in that particular rubber phase upon blending with the second rubber. The flow behavior is measured with an Instron capillary rheometer. The results indicate that the viscosity function of these blends is not sensitive to the mixing conditions. However, the elasticity is always, dependent on mixing. Elasticity is expressed as Δ Pe /σ, where Δ Pe is the entrance pressure drop from the Bagley plot and σ the shear stress. In general, Δ Pe /σ of the blend decreases with increasing mixing.