Carbon black is the predominant reinforcing filler used in rubber compounds and serves to improve durability and strength. For various types of tires, it is used in inner liners, carcasses, sidewalls and treads utilizing different types based on specific performance requirements. Carbon black is also used in molded and extruded industrial rubber products, such as belts, hoses, gaskets, diaphragms, vibration isolation devices, bushings, air springs, chassis bumpers, and multiple types of pads, boots, wiper blades, fascia, conveyor wheels, and grommets.

— Characteristics

Improvement in rubber properties is a function of the physical and chemical characteristics of carbon black – aggregate size, shape and structure, particle size, surface activity, and porosity. Increasing structure or branching typically increases modulus, hardness, electrical conductivity and compound viscosity and improves dispersability of carbon black. Oil absorption is the typically sold as a beaded product (pellets).

Typical carbon black primary particle size ranges from 8 nanometers for furnace blacks to 300 nanometers for thermal blacks. Finer particles increase reinforcement, abrasion resistance, and improve tensile strength. Surface chemistry can affect abrasion resistance, tensile strength, hysteresis and modulus. Higher porosity allows compounders to increase carbon black loading, while maintaining compound specific gravity. This leads to increases in modulus and electrical conductivity for a fixed loading of carbon black.

— Some empirical guidelines in using carbon black:

Increase in carbon black aggregate size or structure

Improves cut growth and fatigue resistance

Decrease in particle size

Increases in abrasion resistance and tear strength. Drop in resilience, and hysteresis and heat buildup

Decrease in carbon black loading

Lowers tire rolling resistance

Increase in fineness

Raises rolling resistance and traction

Increase carbon black loading

Increases in compound heat buildup, harness, rolling resistance, and traction. Tensile strength, processability, and abrasion resistance go through a maximum then decrease and properties deteriorate.