Sustainable Functionalization Of sp2 Carbon Allotropes As Fillers For Rubber Compounds With Lower Dissipation Of Energy

sp2 carbon allotropes are efficient reinforcing fillers for rubber materials: not only carbon black, but also nanofillers such as carbon nanotubes, graphene and graphene related materials. The introduction of functional groups on sp2 carbon allotropes allows to dramatically enlarge their properties portfolio and hence their impact on the properties of rubber materials. In our research Group, a facile and sustainable functionalization method, suitable for all the families of sp2 carbon allotropes, has been developed. Primary amines were combined with α,δ dicarbonyl compounds and pyrrole compounds (PyC) were obtained with high atom economy and yield. Functionalization was obtained by simply mixing the carbon allotropes and the pyrrole compound, giving thermal energy. Reactions were characterized by a yield up to 96%. The structure of the graphitic substrates remained substantially unaltered, after the reaction. Study of the mechanism led to define a domino reaction involving a carbocatalyzed oxidation of the pyrrole compound followed by Diels-Alder cycloaddition. The synthesis of PyC could be performed in situ, on the carbon allotrope. Dispersions of functionalized carbon allotropes were prepared in solvents with different solubility parameters and, from the qualitative results of the dispersion tests, Hansen solubility parameters of carbon allotropes were estimated. Functionalized carbon black was used to prepare rubber compounds based on carbon black and/or silica as the main fillers. The effect on vulcanization behavior and mechanical reinforcement is discussed.