In fact, addition of a barium nitrate to the aqueous solution after treatment showed formation of a white precipitate (BaSO4), indicating the presence of sulfate. Therefore, one can consider that the devulcanization process takes place by oxidation of the sulfur crosslinks with HNO3, producing free polymer chains. This devulcanized polymer is soluble in different organic solvents. On the other hand, the concentrated nitric acid can also react with the polymer carbon backbone by two pathways: (i) nitration and (ii) oxidation. Nitration of styrene polymers with HNO3 is a well known process25, 26 and probably takes place at the aromatic ring