84
5 Reinforcing Mechanism of Rubber by Nanofiller
of CB and is the most important result so far we have obtained. Further, the most
recent relevant studies on the aggregation of CB are explained at Sect. 5.5. Lastly, at
Sect. 5.6, our semiflexible CB network is applied to explaining a mechanical property of CB-loaded rubber vulcanizate, and the crucial utility of the CB structuring
involving bound rubber is concluded.
5.2 Prehistory up to the Beginning of Discussions
on Rubber Reinforcement (Until the Early Second Half
of the Twentieth Century)
The invention of the sulfur vulcanization by C. Goodyear in 1839 blazed a trail in the
practical utilization of rubber, which had been a simply curious elastic material in
Europe for long [1–5]. It has to be noted that NR was the only rubber available then.
G. Oenslager accelerated the development of vulcanization technique by initiating
the use of organic accelerator with sulfur [2–7]. On the other hand, S. C. Mote began
to use CB-loaded NR for tire in 1904 [2, 4, 6]. The two practices, vulcanization
by sulfur/accelerator system and rubber reinforcement by CB loading, are the basic
technical requirement for rubber utilization except a few rubber products involving
a liquid state in their processing, e.g., rubber solution for adhesives and thin film
products manufactured from NR latex.
As explained in Chaps. 1 and 2, it has to be emphasized that rubber reinforcement
by CB has brought about necessary frictional and wear properties to tread rubber of
tires, belts, and lots of other products, as well as mechanical strength. During the
earlier period, therefore, it had been difficult to envision the overall schematic of the
rubber reinforcement, and hence, how to explain the effect of CB on rubber properties had remained unrecognized until the middle of the century. Ref. [6], which was
planned by a committee set up by the Rubber Division of Am. Chem. Soc. and published in 1937, remained one of the standard textbooks for years. It was a big volume
of 941 pages containing 26 chapters. However, only one chapter of 34 pages was
devoted to the description of rubber reinforcement [8]. It occupies only 1/26 = 3.8%
in chapters or 34/941 = 3.6% in pages, in which the present readers may assume
too much underestimation of the significance of rubber reinforcement for any rubber
textbooks. However, this impression seems to be based on a misinterpretation: This
meager description on reinforcement should be understood by the fact that the low
percentages were simply due to the scanty of the decent research papers on rubber
reinforcement then. This scanty is more or less natural, if we now consider the difficulty at the time in disentangling nanometer-level structural complexity associated
with CB particles, which may have been the case in nanosize particles in general.
In spite of this difficulty, the authors of the chapter [8], Shepard, Street, and
Park, prepared a full list of the possible fillers (they used the word ‘pigment’ for
filler in accordance with the usages then) of rubber and checked the list carefully.
Correctly, they concluded that MgCO 2 , ZnO, China clay, lithopone, whiting, baryte,
5 Reinforcing Mechanism of Rubber by Nanofiller
of CB and is the most important result so far we have obtained. Further, the most
recent relevant studies on the aggregation of CB are explained at Sect. 5.5. Lastly, at
Sect. 5.6, our semiflexible CB network is applied to explaining a mechanical property of CB-loaded rubber vulcanizate, and the crucial utility of the CB structuring
involving bound rubber is concluded.
5.2 Prehistory up to the Beginning of Discussions
on Rubber Reinforcement (Until the Early Second Half
of the Twentieth Century)
The invention of the sulfur vulcanization by C. Goodyear in 1839 blazed a trail in the
practical utilization of rubber, which had been a simply curious elastic material in
Europe for long [1–5]. It has to be noted that NR was the only rubber available then.
G. Oenslager accelerated the development of vulcanization technique by initiating
the use of organic accelerator with sulfur [2–7]. On the other hand, S. C. Mote began
to use CB-loaded NR for tire in 1904 [2, 4, 6]. The two practices, vulcanization
by sulfur/accelerator system and rubber reinforcement by CB loading, are the basic
technical requirement for rubber utilization except a few rubber products involving
a liquid state in their processing, e.g., rubber solution for adhesives and thin film
products manufactured from NR latex.
As explained in Chaps. 1 and 2, it has to be emphasized that rubber reinforcement
by CB has brought about necessary frictional and wear properties to tread rubber of
tires, belts, and lots of other products, as well as mechanical strength. During the
earlier period, therefore, it had been difficult to envision the overall schematic of the
rubber reinforcement, and hence, how to explain the effect of CB on rubber properties had remained unrecognized until the middle of the century. Ref. [6], which was
planned by a committee set up by the Rubber Division of Am. Chem. Soc. and published in 1937, remained one of the standard textbooks for years. It was a big volume
of 941 pages containing 26 chapters. However, only one chapter of 34 pages was
devoted to the description of rubber reinforcement [8]. It occupies only 1/26 = 3.8%
in chapters or 34/941 = 3.6% in pages, in which the present readers may assume
too much underestimation of the significance of rubber reinforcement for any rubber
textbooks. However, this impression seems to be based on a misinterpretation: This
meager description on reinforcement should be understood by the fact that the low
percentages were simply due to the scanty of the decent research papers on rubber
reinforcement then. This scanty is more or less natural, if we now consider the difficulty at the time in disentangling nanometer-level structural complexity associated
with CB particles, which may have been the case in nanosize particles in general.
In spite of this difficulty, the authors of the chapter [8], Shepard, Street, and
Park, prepared a full list of the possible fillers (they used the word ‘pigment’ for
filler in accordance with the usages then) of rubber and checked the list carefully.
Correctly, they concluded that MgCO 2 , ZnO, China clay, lithopone, whiting, baryte,