Particulate Fillers in Thermoplastics

Abstract

Carbon black is the generic name for a family of small-size, mostly amorphous, or paracrystalline carbon particles grown together to form aggregates of different sizes and shapes. Carbon black is formed in the gas phase by the thermal decomposition of hydrocarbons in the absence or presence of oxygen in substoichiometric quantities and is industrially manufactured in the form of hundreds of defined commercial grades that vary in their primary particle size, aggregate size and shape, porosity, surface area, and chemistry. Carbon blacks are mainly used as reinforcing fillers in tires and other rubber products. The reinforcement effect is influenced by the interaction between the elastomer molecules, between the carbon black particles themselves, and between the carbon black particles and the elastomer matrix. For elastomer reinforcement, the primary particle size (specific BET surface area) and surface activity of the carbon black types are important as well as their carbon black structure. In addition, the degree of carbon black dispersion achieved and the carbon black loading used in the elastomer composite play a role. The type of carbon black can significantly influence the properties of the resulting rubber compounds. This explains the existence of many different standardized industrial carbon black grades being used in rubber compounds for the body and tread of tires. Carbon blacks are expected to continue to dominate the rubber market for the foreseeable future, but they are coming under considerable pressure from precip- itated silica in some important tire applications. This is because the silica offers lower rolling resistance properties and hence improved fuel economy and lower emissions. This trend is expected to continue to grow. Specialty carbon black grades are used as black color pigments in plastics, paints, and inks, as ultraviolet (UV) stabilizers in polymers to avoid their degra- dation under the influence of visible and UV light, and as fillers to impart electrical conductivity to polymers for electrostatic dissipative and conductive applications.