It is known that the chemical composition of pyrolytic
carbon black
changes considerably after the pyrolysis process of the tire owing
to the presence of a high level of charge which alters the homogeneity
of its surface and therefore affects the efficiency of the interactions
of pyrolytic carbon black with polymers. Thus, when used in composites,
the presence of these impurities causes a nonhomogeneous distribution
of the pyrolytic nanofillers in the matrix. This results in the agglomeration
of the pyrolytic fillers, which limits their effectiveness as reinforcing
materials. Surface treatment techniques have been developed to reduce
the chemical activity of impurities, but innovative practical techniques
to improve the structural surface properties of the pyrolytic filler
enhancing its effectiveness in composites are still needed. To do
so, the main objective of these innovations is to improve the surface
chemical properties to enhance the surface chemical activity of the
pyrolytic black. It is in this context that this work is intended.
The functionalization of the surface of pyrolytic carbon blacks involved
a precise control of oxidation by air, which allowed grafting acidic
oxygen functional groups. The objective is to reinforce the activity
of the surface properties to allow better adhesion between the filler
and the polymers for the possible development of composites with a
plastic matrix. In this study, the functionalization technique is
quite ecological, and the oxidizing agent used was oxygen from air.
This technique made it possible to carry out controlled oxidation
of different samples of pyrolytic carbon black over different initial
temperature ranges (Top), namely, from 25 to 370 °C, from 370
to 385 °C, and above 385 °C. In each experiment, the evolution
of the oxidation temperature of the treated sample was monitored,
and the final product was characterized by a variety of physicochemical
characterization techniques including thermogravimetric analysis,
the physisorption isotherm of nitrogen to determine the specific surface
area (Brunauer–Emmett–Teller method) and diameter and
pore size distribution estimated by nonlocal functional density theory.
Also, the concentration of oxygenated acid functions was evaluated
using Boehm titration, and infrared spectroscopy with Fourier transform
in attenuated total reflection mode ATR–FTIR was carried out
as well on each oxidized sample. Raman spectroscopy was utilized to
examine possible modifications of the carbon ordering. Transmission
electron microscopy was also applied. For samples oxidized over the
initial temperature range of 370–385 °C, the process allowed
generating maximum concentrations of surface acidic oxygen groups
with only insignificant weight loss. Also, the injection of water
vapor at selected oxidation time into the reactor allowed good control
of the local temperature distribution in the sample, which is particularly
important for the temperature of the hot spots likely to form at the
points on the surface where oxidation begins.