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
1. IntroductionSilica and carbon black are reinforcing fillers that arewidely used in rubber. Because of their different surfacecharacteristics, both fillers can form agglomerates but thecause of such agglomeration is not the same, leading to adifference in dispersion ability. The filler–filler interactionof carbon black is mainly generated through relativelyweak Van der Waal forces, which can be readily brokenduring mixing. In contrast, silica agglomeration is due tohydrogen bonding in addition to Van der Waal forces andother physical interactions, leading to a much strongerfiller–filler interaction [1]. Silica has a high polarity and ahydrophilic surface due to silanol groups on its surface.Consequently, silica is incompatible with non-polarrubbers such as natural rubber (NR), styrene–butadienerubber (SBR) and butadiene rubber (BR), but better compatiblewith polar rubbers such as polychloroprene rubber(CR) [2] and acrylonitrile butadiene rubber (NBR) [3]. Useof silica in non-polar rubbers without any compatibilizersresults in poor dispersion and consequently inferior propertiesas a result of these strong filler–filler interactions[4]. In addition, polar functional groups on the silicasurface may form hydrogen bonds with other polar componentsin rubber compounds such as accelerators. So, commonlybasic accelerators are adsorbed on the acidic surfaceof silica which negatively affects cure properties [5].Successful use of silica for rubber reinforcement thereforerequires commonly silane coupling agents to enhancesilica–rubber interaction and silica dispersion as well asto prevent accelerator adsorption on the silica surface.Some polar rubbers bearing functional groups whichcan interact with the silica surface have been studied as
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