Carbon blacks and silicas of varying forms and particlesizes
are very popular and have been widely utilized as
reinforcing fillers in the rubber industry. In general, the
properties of silica-reinforced rubber vulcanisates are
usually inferior to those of carbon blacks, even when they
are of comparable size [1]. This is attributed to the apparent
dissimilarity in the surface chemistry of the two materials.
Carbon black will react with sulphur during vulcanization
and form sulphur bonds that link the rubber chains, and
also tie the carbon black to the rubber. This is known as
filler-rubber crosslinking, another type of crosslink to the
rubber system, and is defined as coupling bonds [2,3]. In
marked contrast to the hydrocarbon functionality of carbonblack, silica does not react with sulphur, and coupling
bonds will not be formed due to its hydrophilic silanol
groups that are relatively incompatible with hydrocarbon
rubbers, such as natural rubber [2].