The present study aimed to prepare a novel efficient flame retardant additive for polypropylene. The new flame retardant was prepared by chemical grafting of melamine to graphene oxide with the aid of thionyl chloride. Fourier-transform infrared spectroscopy and thermogravimetric analysis proved that melamine had been successfully grafted to the graphene oxide. The modified graphene oxide was incorporated into polypropylene via solution mixing followed by anti-solvent precipitatio. Homogeneous distribution as well as exfoliation of the nanoplatelets in the polymer matrix was observed using transmission electron microscopy. Thermogravimetric analysis showed a significant improvement in the thermo-oxidative stability of the polymer after incorporating 2 wt% of the modified graphene oxide. The modified graphene oxide also enhanced the limiting oxygen index of the polymer. However, the amount of improvement was not enough for the polymer to be ranked as a self-extinguishing material. Cone calorimetry showed that incorporating 2 wt% of the modified graphene oxide lowered total heat release and the average production rate of carbon monoxide during burning of the polymer by as much as 40 and 35%, respectively. Hence, it was concluded that the new flame retardant can retard burning of the polymer efficiently and profoundly reduce suffocation risk of exposure to burning polymer byproducts.

Abstract
 1. Introduction
 2. Experimental
  2.1. Materials
  2.2. Grafting of melamine on the grapheneoxide nanoplatelets
  2.3. Preparation of nanocomposite samples
  2.4. Characterization
 3. Results and Discussion
  3.1. Investigation of occurrence of the graftingreaction
  3.2. Assessment of state of dispersion in theprepared nanocomposite samples
  3.3. Evaluation of the heat stability and flameresistance of the prepared samples
 4. Conclusions
 References

• Parisa Monji(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
• Milad Mehranpour(Department of Polymer Engineering, Science and Research Branch, Islamic Azad University)