In the present work, capability of thymolphthalein-grafted graphene oxide, which was successfully synthesized in this study, in stabilization of polypropylene against thermal oxidation were investigated and compared with that of SONGNOX 1010, a commercially used phenolic antioxidant for the polymer. The modified graphene oxide were incorporated into polypropylene via melt mixing. State of distribution of the nanoplatelets in the polymer matrix was examined using scanning electron microscopy and was shown to be homogeneous. Measurements of oxidation onset temperature and oxidative induction time revealed that thymolphthalein-grafted graphene oxide modifies thermo-oxidative stability of the polymer in the melt state remarkably. However, the efficiency of the nanoplatelets in stabilization of polypropylene against thermal oxidation in melt state was shown to be inferior to that of SONGNOX 1010. Furthermore, oven ageing experiments followed by Fourier transform infrared spectroscopy showed that the modified graphene oxide improves thermo-oxidative stability of the polymer strongly in the solid state, so that its stabilization efficiency is comparable to that of SONGNOX 1010.

Abstract
 1. Introduction
 2. Experimental
  2.1. Materials
  2.2. Sample preparation
  2.3. Characterization
  2.4. Thermo-oxidative degradation of thesamples in melt state
  2.5. Thermo-oxidative degradation of thesamples in solid state
 3. Results and Discussion
  3.1. Characterization of the chemically modifiedgraphene oxide
  3.2. Evaluation of antioxidant efficiency ofthe chemically modified graphene oxide
 Conflict of Interest
 References

• Mona Bagheripour-Asl(Department of Polymer Engineering, Science and Research Branch, Islamic Azad University)
• Reza Jahanmardi(Department of Polymer Engineering, Science and Research Branch, Islamic Azad University) Corresponding Author
• Hasan Tahermansouri(Department of Chemistry, Ayatollah Amoli Branch, Islamic Azad University)
• Erfan Forghani(Department of Polymer Engineering, Science and Research Branch, Islamic Azad University)