The prime application of elastomeric composites is tire compounds. The tuning of
dynamic rigidity and hysteresis is key to achieve the desired tire performances. Car
tires require hysteresis to be high at low temperatures, to promote wet traction, and
low at medium-high temperatures, for low energy dissipations. To achieve these
properties amorphous precipitated silica is commonly selected as reinforcing filler due
to its nano dimensions and the possibility of establishing chemical bonds with the
elastomers’ chains. Carbon black (CB), another common filler for tire compounds, does
not have functional groups able to promote chemical bonds with the rubber matrix yet
it would be highly desirable. A CB with a cradle to gate LCA comparable if not even
better than silica’s LCA could be used in replacement of silica in tire compounds.
In this work, a pyrrole compound (PyC) containing a thiol group was used to
functionalize CB by the so-called “pyrrole methodology” . The thiol group was
expected to react with the sulphur-based crosslinking system, thus forming chemical
bonds with the rubber chains. The synthesis of the PyC and the functionalization
reaction were characterized by high atom efficiency. A poly(styrene-co-butadiene)
copolymer from anionic solution polymerization was used as the main rubber for the
compound preparation. The crosslinked composite material filled with functionalized
CB revealed substantial improvements with respect to the composite with pristine CB,
in particular: high rigidity and low hysteresis at high temperature. These findings seem
to confirm the formation of the expected rubber-filler chemical bond and are even
comparable to those of silica- based rubber composites. The results here reported pave
the way to CB-based rubber composites with a low environmental impact
