86
5 Reinforcing Mechanism of Rubber by Nanofiller
A. R. Payne gave an excellent review (again see Sect. 2.5) on rubber reinforcement
[10], together with the very well-written chapters, Chap. 1 (by Bueche), Chap. 4 (by
Kraus), Chap. 6 (by Hess), and Chap. 12 (by Studebaker). This publication is the
first book focused on rubber reinforcement in particular and has been the so-called
bible on rubber reinforcement until quite a recent time.
Summing up, the excellent review on the rubber reinforcement by the three
researchers (Shepard, Street, and Park) was followed by lots of studies on the relevant subjects. In 1965, the book on rubber reinforcement was edited by G. Kraus and
published, which well summarized both scientific and practical aspects of the topics
then. This book, thus, had stimulated rubber scientists and engineers to give rise to
a new stage of the studies on rubber reinforcement.
5.3 Progress in the Modeling of Rubber Reinforcement
(Until the End of the Twentieth Century)
The development of the new stage is characterized by several proposals of the working hypothesis on the mechanism of rubber reinforcement. On CB in particular,
further studies on bound rubber and aggregation of CB up to the agglomeration were
researched extensively. In the second half of the 1990s, these efforts finally focused
on the agglomerate, whether it was a network structure of CB or not, and hence,
this section covers the period just before the empirical substantiation of the filler
network early in the twenty-first century. In this connection, the influence from the
non-rubber field is to be mentioned here. CB is an electron-conducting filler, and lots
of studies of conductive CB/polymer composites have been published, specifically
on the observed percolation phenomenon [11–14]. In other words, CB is supposed to
form a network structure to afford electron-conductive path. This somewhat outside
situation influenced the rubber technology field because electron-conductive rubbers
containing CB are well within the rubber composite arena.
Early in the second half of the twentieth century, the proposed hypotheses were
on channel or thermal CB not on the furnace one, which was becoming popular
in the 1960s and is now in use predominantly in the rubber industry. Because the
former CBs carried more chemically reactive groups on their surface than furnace
black, chemical bonding between filler surface and rubber was assumed quite often.
Two examples are displayed in Figs. 5.1 and 5.2 [15–18]. The former may have
suggested either the presence of more cross-linking point of rubber around the CB
particle or the bound rubber being formed by the cross-linked rubber. Anyway, the
important is the chemical bonding between rubber and filler surface in the present
context. Figure 5.2 suggests three kinds of rubber chain differentiated by its length.
A is highly stretched under strain, B is strained a little, and C is not under strain.
The presence of three kinds of rubber chains in the figure was assumed to explain
the Mullins effect [16]. Yet the three chains are chemically connected to the CB
surface. Bueche explained the reinforcement effect of CB per Fig. 5.2, that is, it was
5 Reinforcing Mechanism of Rubber by Nanofiller
A. R. Payne gave an excellent review (again see Sect. 2.5) on rubber reinforcement
[10], together with the very well-written chapters, Chap. 1 (by Bueche), Chap. 4 (by
Kraus), Chap. 6 (by Hess), and Chap. 12 (by Studebaker). This publication is the
first book focused on rubber reinforcement in particular and has been the so-called
bible on rubber reinforcement until quite a recent time.
Summing up, the excellent review on the rubber reinforcement by the three
researchers (Shepard, Street, and Park) was followed by lots of studies on the relevant subjects. In 1965, the book on rubber reinforcement was edited by G. Kraus and
published, which well summarized both scientific and practical aspects of the topics
then. This book, thus, had stimulated rubber scientists and engineers to give rise to
a new stage of the studies on rubber reinforcement.
5.3 Progress in the Modeling of Rubber Reinforcement
(Until the End of the Twentieth Century)
The development of the new stage is characterized by several proposals of the working hypothesis on the mechanism of rubber reinforcement. On CB in particular,
further studies on bound rubber and aggregation of CB up to the agglomeration were
researched extensively. In the second half of the 1990s, these efforts finally focused
on the agglomerate, whether it was a network structure of CB or not, and hence,
this section covers the period just before the empirical substantiation of the filler
network early in the twenty-first century. In this connection, the influence from the
non-rubber field is to be mentioned here. CB is an electron-conducting filler, and lots
of studies of conductive CB/polymer composites have been published, specifically
on the observed percolation phenomenon [11–14]. In other words, CB is supposed to
form a network structure to afford electron-conductive path. This somewhat outside
situation influenced the rubber technology field because electron-conductive rubbers
containing CB are well within the rubber composite arena.
Early in the second half of the twentieth century, the proposed hypotheses were
on channel or thermal CB not on the furnace one, which was becoming popular
in the 1960s and is now in use predominantly in the rubber industry. Because the
former CBs carried more chemically reactive groups on their surface than furnace
black, chemical bonding between filler surface and rubber was assumed quite often.
Two examples are displayed in Figs. 5.1 and 5.2 [15–18]. The former may have
suggested either the presence of more cross-linking point of rubber around the CB
particle or the bound rubber being formed by the cross-linked rubber. Anyway, the
important is the chemical bonding between rubber and filler surface in the present
context. Figure 5.2 suggests three kinds of rubber chain differentiated by its length.
A is highly stretched under strain, B is strained a little, and C is not under strain.
The presence of three kinds of rubber chains in the figure was assumed to explain
the Mullins effect [16]. Yet the three chains are chemically connected to the CB
surface. Bueche explained the reinforcement effect of CB per Fig. 5.2, that is, it was