1.3 Reinforcement of Cross-Linked Rubber by Particulate Nanofiller
9
survive through the avalanche of synthetic new rubbers, and during the past several
decades its share in the rubber market has kept 40% or above, and it is predicted that
it could be over 50% in the near future.
In this era of coexistence of NR and synthetic rubbers, CB consumption in rubber
industry is continuously increasing, since the CB mixing is of more necessity when
using synthetic diene rubbers such as SBR, NBR (acrylonitrile-butadiene rubber),
and CR (chloroprene rubber) than in NR. Specifically on the comparative reinforcing
effect of CB on NR and SBR, see Fig. 8.7 in Chap. 8. Predominance of CB in rubber
reinforcement is expanding with the increase of synthetic rubber usage. Accordingly,
even after the arrival of synthetic ones in the rubber market, many of rubber products
are CB-loaded rubber vulcanizates, and they are now recognized simply as ‘rubber’
by the general public.
Recently, the use of particulate silica is increasing in addition to CB. It is sure
that silica shows some characteristics superior to CB, but a few outside factors are
involved: The source of CB being petroleum has been proved to be problematic,
since the production of petroleum is much localized and is believed to be exhausting.
In fact, ‘decarbonization’ is a trend in this century. On the other hand, the source
of silica is abundant everywhere on the earth. Also, silicon chemistry has a long
research history both in organic and inorganic arenas [28], and silicone elastomer
is occupying an important position among specialty rubbers. Particulate silica of
nanometer radius is available, and it is applicable to not only silicone rubber but
many other rubbers including NR and SBR. Hence, silica is alternative to CB for a
rubber reinforcing nanofiller, and lots of technical studies are reported up to now.
Compared with CB, surface modifications of silica particle are much easier, and
utilization of silane coupling agents has been one important area of studies in rubber
reinforcement [29–34]. Chapter 7 is dedicated to silica reinforcement.
1.4 Development of Soft Nanocomposite
Manufacturing and consumption of the CB-loaded NR vulcanizate have been more
than satisfactory, even after the introduction of synthetic ones as described in the previous subsections. Further, rubber composites from the rubber mixed with nanofiller
are soft, i.e., highly stretchable and recoverable to afford the repeated stretching.
These unique features, which are the characteristic of rubber elasticity [1, 3–5, 8, 11,
35–38], have enabled them to survive through the Era of Nanotechnology [39, 40].
In a sense, the use of nanofiller for rubber composites has been quite common, and
we do not need to use the word ‘nano,’ since the rubber reinforcing filler was well
recognized to be a nanosize particle even before 1960s [5], which is to be discussed
more in Chapter 2. Among lots of fillers for rubber, nanofillers whose radii are of
several or a few tens nanometers including CB and silica have been in conventionally
used in rubber industry all over the world. This book is concerned mainly on rubber
reinforcement mechanism, not aiming an exhaustive account on rubber reinforcement. Therefore, CB and silica are under consideration here. The two have been
9
survive through the avalanche of synthetic new rubbers, and during the past several
decades its share in the rubber market has kept 40% or above, and it is predicted that
it could be over 50% in the near future.
In this era of coexistence of NR and synthetic rubbers, CB consumption in rubber
industry is continuously increasing, since the CB mixing is of more necessity when
using synthetic diene rubbers such as SBR, NBR (acrylonitrile-butadiene rubber),
and CR (chloroprene rubber) than in NR. Specifically on the comparative reinforcing
effect of CB on NR and SBR, see Fig. 8.7 in Chap. 8. Predominance of CB in rubber
reinforcement is expanding with the increase of synthetic rubber usage. Accordingly,
even after the arrival of synthetic ones in the rubber market, many of rubber products
are CB-loaded rubber vulcanizates, and they are now recognized simply as ‘rubber’
by the general public.
Recently, the use of particulate silica is increasing in addition to CB. It is sure
that silica shows some characteristics superior to CB, but a few outside factors are
involved: The source of CB being petroleum has been proved to be problematic,
since the production of petroleum is much localized and is believed to be exhausting.
In fact, ‘decarbonization’ is a trend in this century. On the other hand, the source
of silica is abundant everywhere on the earth. Also, silicon chemistry has a long
research history both in organic and inorganic arenas [28], and silicone elastomer
is occupying an important position among specialty rubbers. Particulate silica of
nanometer radius is available, and it is applicable to not only silicone rubber but
many other rubbers including NR and SBR. Hence, silica is alternative to CB for a
rubber reinforcing nanofiller, and lots of technical studies are reported up to now.
Compared with CB, surface modifications of silica particle are much easier, and
utilization of silane coupling agents has been one important area of studies in rubber
reinforcement [29–34]. Chapter 7 is dedicated to silica reinforcement.
1.4 Development of Soft Nanocomposite
Manufacturing and consumption of the CB-loaded NR vulcanizate have been more
than satisfactory, even after the introduction of synthetic ones as described in the previous subsections. Further, rubber composites from the rubber mixed with nanofiller
are soft, i.e., highly stretchable and recoverable to afford the repeated stretching.
These unique features, which are the characteristic of rubber elasticity [1, 3–5, 8, 11,
35–38], have enabled them to survive through the Era of Nanotechnology [39, 40].
In a sense, the use of nanofiller for rubber composites has been quite common, and
we do not need to use the word ‘nano,’ since the rubber reinforcing filler was well
recognized to be a nanosize particle even before 1960s [5], which is to be discussed
more in Chapter 2. Among lots of fillers for rubber, nanofillers whose radii are of
several or a few tens nanometers including CB and silica have been in conventionally
used in rubber industry all over the world. This book is concerned mainly on rubber
reinforcement mechanism, not aiming an exhaustive account on rubber reinforcement. Therefore, CB and silica are under consideration here. The two have been