The recycled pyrolytic carbon black(PC) from used tyre was obtained by atmospheric pyrolysis with a small degree of aggregation

small surface area

and a lot of ashes and carbonaceous deposits. The PC was modified by a series of chemical treatment with nitric acid and nitric acid/stearic acid. Inverse gas chromatography was used to assess the consequence of the modifications. In particular

inverse gas chromatography at infinite dilution was shown to detect essentially the most active sites

and allows monitoring of the variation of surface properties upon chemical modifications of the PC. Inverse gas chromatography at finite concentration was used to characterize the surface energy site distribution.There are many structural defects on pyrolytic carbon black and the surface energy is heterogeneously distributed. In conclusion

nitric acid could decrease the surface carbonaceous deposits

and make more active sites. The retreatment of pyrolytic carbon black with stearic acid would

on one hand

diminish the particle-particle interactions and hence facilitate the dispersion of the filler in the natural rubber matrix and

on the other hand

enhance the compatibility between filler and matrix leading to better mechanical performance of the composite.