34
2 Filler and Rubber Reinforcement
He compared various types of CB (Fig. 3.16 in Ref. [85]), and hence, initially in
his mind, the effect of the sort of CB might have been assumed to be the effect of
structure. CBs shown in Table 2.1 are of various diameters as well as various surface
properties or surface structures, and these differences are often said to be due to
the different chemical structures of CB. Since the second factor (Strong links) was
on filler-to-rubber interaction, next third factor (Structure) was reasonably on fillerto-filler interaction, and he gave the title ‘Carbon Black-Carbon Black Structure’
afterward. Accordingly, most of the researchers who worked on the Payne effect
must have thought of higher-order structures of CB aggregates or agglomerates.
Payne himself cited Van den Tempel’s paper [127], but this paper did not propose a
good model enough to be evaluated for the filler structure.
Payne himself describes some experimental results in Figs. 3.24 and 3.25, both
in Ref. [85], which suggested that CB dispersed in liquid paraffins showed a similar behavior to CB in rubber. Here, he suggested the importance of filler-to-filler
interactions to the Payne effect. Consequently, most papers on the Payne effect have
assumed filler network formation so far [128], supposedly without hesitation. However, any scientific evidence for the essential result, i.e., the network structure of
filler had remained unknown until the turn of the century. Probably due to the lack
of experimental evidences, many rubber engineers who were on the side of bound
rubber and/or who were not much interested in the Payne effect believed in more
traditional idea, i.e., ‘the better is the dispersion of CB, the better is the mechanical
properties of rubber.’ This thesis is not bad at all, but the meaning of ‘good dispersion’ is problematic. Even in 1998, a publication states on a found fact that improved
the properties [129]:
…due to the improvement of filler dispersion and its stabilization, or preventing the filler
network formation and filler aggregation by introducing chemical reactions of functional
polymer molecules with some active sites of CBs during the mixing process.
They assumed that good dispersion of CB might be realized by preventing the filler
network formation. For them, the best dispersion means the presence of single filler
particle randomly (the filler-to-rubber interaction is dominating over the filler-to-filler
interaction) in the rubber matrix.
While bound rubber is established experimentally in the rubber arena, a little
different situation has been dominating in the arena of the conductive composites,
where the matrix has been polymers including plastics and/or rubbers. In lots of
the electron-conductive polymer composites where electro-conductive fillers (CB,
maybe of different grades from HAF or ISAF, is one of them) are dispersed in polymer
matrix, percolation [130] is observed, and the formation of filler networks in polymer
matrix is reasonably estimated in explaining the observed percolation phenomena
[131]. There, ‘bound polymer’ has not been substantiated in the arena of conductive
polymer composites.
An aspect of these somewhat difficult situations of filler structuring was reflected
in a good review published in early twenty-first century [132]. While the difficulty of
presenting evidence of network formation was persisting, a few groups have started
2 Filler and Rubber Reinforcement
He compared various types of CB (Fig. 3.16 in Ref. [85]), and hence, initially in
his mind, the effect of the sort of CB might have been assumed to be the effect of
structure. CBs shown in Table 2.1 are of various diameters as well as various surface
properties or surface structures, and these differences are often said to be due to
the different chemical structures of CB. Since the second factor (Strong links) was
on filler-to-rubber interaction, next third factor (Structure) was reasonably on fillerto-filler interaction, and he gave the title ‘Carbon Black-Carbon Black Structure’
afterward. Accordingly, most of the researchers who worked on the Payne effect
must have thought of higher-order structures of CB aggregates or agglomerates.
Payne himself cited Van den Tempel’s paper [127], but this paper did not propose a
good model enough to be evaluated for the filler structure.
Payne himself describes some experimental results in Figs. 3.24 and 3.25, both
in Ref. [85], which suggested that CB dispersed in liquid paraffins showed a similar behavior to CB in rubber. Here, he suggested the importance of filler-to-filler
interactions to the Payne effect. Consequently, most papers on the Payne effect have
assumed filler network formation so far [128], supposedly without hesitation. However, any scientific evidence for the essential result, i.e., the network structure of
filler had remained unknown until the turn of the century. Probably due to the lack
of experimental evidences, many rubber engineers who were on the side of bound
rubber and/or who were not much interested in the Payne effect believed in more
traditional idea, i.e., ‘the better is the dispersion of CB, the better is the mechanical
properties of rubber.’ This thesis is not bad at all, but the meaning of ‘good dispersion’ is problematic. Even in 1998, a publication states on a found fact that improved
the properties [129]:
…due to the improvement of filler dispersion and its stabilization, or preventing the filler
network formation and filler aggregation by introducing chemical reactions of functional
polymer molecules with some active sites of CBs during the mixing process.
They assumed that good dispersion of CB might be realized by preventing the filler
network formation. For them, the best dispersion means the presence of single filler
particle randomly (the filler-to-rubber interaction is dominating over the filler-to-filler
interaction) in the rubber matrix.
While bound rubber is established experimentally in the rubber arena, a little
different situation has been dominating in the arena of the conductive composites,
where the matrix has been polymers including plastics and/or rubbers. In lots of
the electron-conductive polymer composites where electro-conductive fillers (CB,
maybe of different grades from HAF or ISAF, is one of them) are dispersed in polymer
matrix, percolation [130] is observed, and the formation of filler networks in polymer
matrix is reasonably estimated in explaining the observed percolation phenomena
[131]. There, ‘bound polymer’ has not been substantiated in the arena of conductive
polymer composites.
An aspect of these somewhat difficult situations of filler structuring was reflected
in a good review published in early twenty-first century [132]. While the difficulty of
presenting evidence of network formation was persisting, a few groups have started