Mixing of Carbon Black with Rubber. VI. Analysis of NR/SBR Blends

Abstract

Abstract The distribution of carbon black in NR/SBR blends was determined through the analysis of bound rubber. The NR/SBR blends were found to be very different from the previously studied SBR/BR compounds: these differences were assigned to mutual insolubility of the two polymers and a very high molecular weight of NR. In NR/SBR blends, it was found that changes in molecular weight of the polymer has no effect on the carbon black distribution in the blend. While the “activity” of carbon black did not affect the distribution, the loading of the black in NR decreased linearly with increasing surface area of the black. Approximately 35% of normal tread blacks (surface area 80–100 m2/g) was found in the NR phase. However, the bond between NR and carbon black is quite weak, and black continues to migrate into the SBR phase on prolonged mixing or during blending of NR and SBR masterbatches.