Reinforcement of Elastomers by Carbon Black

Abstract

The reinforcement of elastomers by carbon black is governed by the morphology of the black and its physical and chemical interactions with the polymer. The latter are strongly affected by graphitization and surface oxidation. In modern rubber-grade carbon blacks strong bonding of the polymer to the carbon black surface is effected by several mechanisms, but surface chemical differences between blacks are relatively small, so that the dominant characteristic becomes the morphology. This is determined by the average size and size distribution of the particles which are fused together to form primary aggregates resembling branched random coils, the spatial arrangement of the particles in these aggregates, and the number of particles per aggregate and its distribution. This highly complex morphology can, to a first approximation, be represented by the specific surface area accessible to rubber and some, usually indirect, measure of the volume pervaded by the primary aggregates (“structure”). Important mechanical properties of reinforced rubbers depend to different degrees on these two characteristics, often in rather complex manner. Their effects on viscoelastic and failure properties are described. Additionally, some very recent observations on the effects of carbon black on network structure and the influence of the breadth of the aggregate size distribution on viscoelastic behavior are discussed.

Characterisation of Surface Activity of Carbon Black and its Relation to Polymer‐Filler Interaction

“…Significant effects of the different grades of carbon blacks in elastomer composites result from variations in the specific surface and/or ''structure'' of the primary aggregates. [1,2] The specific surface depends strongly on the size of the primary particles and differs from about 10 m 2 Á g À1 for the very coarse blacks up to almost 200 m 2 Á g À1 for the fine blacks. The ''structure'' of the primary aggregates describes the amount of void volume and is measured, for example, by oil (DBP) absorption.…”

“…The reinforcing properties of carbon blacks are closely related to the fractal nature of the particulate filler aggregates, [1,2] and filler networking, [3,4] which takes place above a percolation limit for sufficient high filler concentration. [5,6] Several recent research activities deal with the reinforcement mechanisms in disordered systems, where the main attention is to gain insight into the relationship between disordered filler structures on different length scales and specific microscopic effects contributing to reinforcement.…”

“…[9] Beside these well investigated morphological effects, the surface activity of carbon blacks plays a key role in reinforcement of elastomers by controlling the polymer-filler phase bonding and the filler-filler interaction. [1,2] Despite this importance of the surface activity, reinforcing fillers are characterised mainly by their specific surface area (mean particle size) and their DBP-or crushed DBP-number (aggregate structure). A standard molecular parameter for the surface activity is still missing.…”

Effect of the doses and nature of vegetable oil on carbon black/rubber interactions: Studies on castor oil and other vegetable oils

“…This is due to the polar-polar interaction. 5,6 For hydrocarbon rubbers such as natural rubber (NR) and styrene-butadiene rubber, the possible interactions with carbon black are physical and physicochemical through double bonds of the main chain. The interactions between hydrocarbon rubbers and carbon black can be improved greatly by the introduction of the coupling action of some particular additives.…”

Rubber elasticity

“…A particularly challenging problem is the development of a more quantitative molecular understanding of the effects of filler particles, such as carbon black in natural rubber (52)(53)(54) and silica in silicone polymers (53,55). Such fillers provide tremendous reinforcement in elastomers, and how they do this is still only poorly comprehended.…”