Study on the Effect of Selection Point Range on the Specific Surface Area and External Surface Area of Carbon Black Samples
Carbon black is produced through the incomplete combustion or thermal decomposition of hydrocarbon feedstocks and is widely used as a reinforcing agent in rubber. More than 90% of global carbon black output is consumed by the rubber industry. When incorporated into a rubber matrix, carbon black enhances key mechanical properties—including hardness, tensile strength, and abrasion resistance—while also improving compound processability and lowering overall formulation cost. Among commercial reinforcing fillers, carbon black remains the most important, and its specific surface area is a primary factor governing reinforcement performance.(1) The specific surface area of carbon black is typically divided into internal and external components. The external specific surface area is especially relevant for evaluating reinforcement because effective reinforcement requires intimate contact between carbon black particles and rubber polymer chains. When the pores on the carbon black surface are too small for rubber molecules to enter, the internal surface associated with these ultrafine pores does not contribute to reinforcement and must be excluded. Therefore, the external specific surface area is defined as the portion of the total surface area remaining after subtracting the internal surface area of pores with diameters ≤ 2 nm that are inaccessible to rubber.(2,3) This application note investigates how different selection-point ranges influence the measured total specific surface area and external specific surface area of carbon black samples.
