20
2 Filler and Rubber Reinforcement
be a good candidate of reinforcing nanofiller for rubber. Such developments are now
under investigation on various minerals and organics.
The progress of nanotechnology (see 1.4), especially on nanoparticles, may
enhance the possibility of them more to the arena of functional nanofillers for rubber in a near future as well as to that of rubber reinforcement. Or, rubber engineers’
experience on these particles may help them to start innovative studies on the specific
functionalization of nanofillers in a different arena from rubber.
2.4 Reinforcing Nanofiller
2.4.1 Introduction to Reinforcing Filler
For rubber reinforcement, reinforcing fillers (mainly nanofiller for a moment) are of
course the most important, and carbon black (CB) and particulate silica are the two
main nanofillers for rubber so far. By the development of nanotechnology, lots of
nanoparticles are introduced, but most of them are subject to novel and sophisticated
functionalization, for the purpose of preparing the device displaying a certain specific
chemical and/or biochemical function. Therefore, they are not chemically stable but
reactive. This is against the chemical stability that the reinforcing nanoparticles have
to show at first when to be used in rubber. Their possibility in the rubber arena may
be limited to that of the functional fillers. CB is a carbon allotrope, and the other
allotropes, e.g., carbon nanotube and graphene are now under active investigation.
For a moment, however, the research tends to functionalization of rubber composites
using modified nanotube or graphene, not much on the reinforcing effects.
Recently, nanofiber is also focused and may suggest the possibility of a tire cord,
but not that of reinforcing filler. Alternatively, if nanofiber is chopped into a short
fiber, random orientation and homogeneous dispersion of the short fiber in rubbery
matrix are realized, and it may possibly become unique reinforcing material for
rubber. Lignin has actively been investigated for its reinforcement effect on rubber
from 1950s. The effect itself has been confirmed, but the lignin composites of rubber
are not amenable to easy processing. This possibility is to be treated later in Chap. 7.
2.4.2 Carbon Black (CB)
CB is a kind of soot and is manufactured by burning organic compounds under a
controlled condition. Industrially manufactured CBs are listed in Table 2.1. Among
them, the reinforcing CBs are manufactured by the oil furnace method, and the
diameters are smaller than 50 nm. For instance, HAF and ISAF are widely used in the
tread rubber of automobile tires. As mentioned in the previous subsection, together
2 Filler and Rubber Reinforcement
be a good candidate of reinforcing nanofiller for rubber. Such developments are now
under investigation on various minerals and organics.
The progress of nanotechnology (see 1.4), especially on nanoparticles, may
enhance the possibility of them more to the arena of functional nanofillers for rubber in a near future as well as to that of rubber reinforcement. Or, rubber engineers’
experience on these particles may help them to start innovative studies on the specific
functionalization of nanofillers in a different arena from rubber.
2.4 Reinforcing Nanofiller
2.4.1 Introduction to Reinforcing Filler
For rubber reinforcement, reinforcing fillers (mainly nanofiller for a moment) are of
course the most important, and carbon black (CB) and particulate silica are the two
main nanofillers for rubber so far. By the development of nanotechnology, lots of
nanoparticles are introduced, but most of them are subject to novel and sophisticated
functionalization, for the purpose of preparing the device displaying a certain specific
chemical and/or biochemical function. Therefore, they are not chemically stable but
reactive. This is against the chemical stability that the reinforcing nanoparticles have
to show at first when to be used in rubber. Their possibility in the rubber arena may
be limited to that of the functional fillers. CB is a carbon allotrope, and the other
allotropes, e.g., carbon nanotube and graphene are now under active investigation.
For a moment, however, the research tends to functionalization of rubber composites
using modified nanotube or graphene, not much on the reinforcing effects.
Recently, nanofiber is also focused and may suggest the possibility of a tire cord,
but not that of reinforcing filler. Alternatively, if nanofiber is chopped into a short
fiber, random orientation and homogeneous dispersion of the short fiber in rubbery
matrix are realized, and it may possibly become unique reinforcing material for
rubber. Lignin has actively been investigated for its reinforcement effect on rubber
from 1950s. The effect itself has been confirmed, but the lignin composites of rubber
are not amenable to easy processing. This possibility is to be treated later in Chap. 7.
2.4.2 Carbon Black (CB)
CB is a kind of soot and is manufactured by burning organic compounds under a
controlled condition. Industrially manufactured CBs are listed in Table 2.1. Among
them, the reinforcing CBs are manufactured by the oil furnace method, and the
diameters are smaller than 50 nm. For instance, HAF and ISAF are widely used in the
tread rubber of automobile tires. As mentioned in the previous subsection, together