Controlled Ingredient-Distribution Mixing: Effect on Some Properties of Elastomer Blend Compounds

The crack growth and heat buildup of carbon black loaded rubber blends were studied as a function of the distribution of carbon black in the individual rubber phases. The blends are styrene-butadiene rubber/polybutadiene (SBR/PBD), natural rubber/cis-polybutadiene (NR/PBD), and styrene-butadiene copolymer/butadiene-acrylonitrile copolymer (SBR/NBR). Regardless of the difference in chemical structure of these rubber blends, the results show that a better crack-growth resistance compound contains proportionately more carbon black in the major rubber phase. A simple analogy of rubber blends to the rubber-modified thermoplastics is proposed to interpret these findings. The heat buildup of the blends is also affected by the distribution of carbon black. However, the extent of the carbon black distribution effect is influenced by the total amount of carbon black in the blends.