1. Introduction
Silica and carbon black are reinforcing fillers that are
widely used in rubber. Because of their different surface
characteristics, both fillers can form agglomerates but the
cause of such agglomeration is not the same, leading to a
difference in dispersion ability. The filler–filler interaction
of carbon black is mainly generated through relatively
weak Van der Waal forces, which can be readily broken
during mixing. In contrast, silica agglomeration is due to
hydrogen bonding in addition to Van der Waal forces and
other physical interactions, leading to a much stronger
filler–filler interaction [1]. Silica has a high polarity and a
hydrophilic surface due to silanol groups on its surface.
Consequently, silica is incompatible with non-polar
rubbers such as natural rubber (NR), styrene–butadiene
rubber (SBR) and butadiene rubber (BR), but better compatible
with polar rubbers such as polychloroprene rubber
(CR) [2] and acrylonitrile butadiene rubber (NBR) [3]. Use
of silica in non-polar rubbers without any compatibilizers
results in poor dispersion and consequently inferior properties
as a result of these strong filler–filler interactions
[4]. In addition, polar functional groups on the silica
surface may form hydrogen bonds with other polar components
in rubber compounds such as accelerators. So, commonly
basic accelerators are adsorbed on the acidic surface
of silica which negatively affects cure properties [5].
Successful use of silica for rubber reinforcement therefore
requires commonly silane coupling agents to enhance
silica–rubber interaction and silica dispersion as well as
to prevent accelerator adsorption on the silica surface.
Some polar rubbers bearing functional groups which
can interact with the silica surface have been studied as