Chemical incorporation of epoxy-modified graphitic layers in epoxy/novolac phenolic resin matrices was carried out through co-curing of epoxy and novolac resins using triphenylphosphine as catalyst. First, (3-glycidyloxypropyl) trimethoxysilane (GPTMS) was grafted on graphene oxide (GO) surface to obtain epoxidized GO layers. Then epoxy resin and GPTMS-modified GO were incorporated into thermosetting reaction using novolac resin in the presence of triphenylphosphine. Covalent attachment of GPTMS-modified GO to the resin matrices resulted in a hybrid composite with high thermal characteristics. Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction, and Raman spectroscopy were used for approving modification of GO with GPTMS. The images resulted from scanning and transmission electron microscopies exhibited GO layers with lots of creases turning to smooth layers with a few thin ripples after modification with GPTMS. TGA results showed that thermal characteristics of resins were improved by the addition of GPTMS-modified GO. Char residue of the hybrid composites containing 0.5 and 1 wt% of GPTMS-modified GO reached 28.1 and 34.3%, respectively. Also, their maximum thermal degradation temperature was also increased by the incorporation of GPTMS-modified GO.

Abstract
1 Introduction
2 Experimental
    2.1 Materials
    2.2 Preparation of GO
    2.3 Preparation of GOG by the modification of GOwith GPTMS
    2.4 Preparation of GOG and epoxy/novolac resincomposites (CENG0.5 and CENG1)
    2.5 Characterization
3 Results and discussion
4 Conclusions
Compliance with ethical standards
References

• Hamidreza Ebrahimi(Faculty of Polymer Engineering, Sahand University of Technology)
• Hossein Roghani‑Mamaqani(Faculty of Polymer Engineering, Sahand University of Technology, Institute of Polymeric Materials, Sahand University of Technology)
• Mehdi Salami‑Kalajahi(Faculty of Polymer Engineering, Sahand University of Technology, Institute of Polymeric Materials, Sahand University of Technology)
• Sina Shahi(Faculty of Polymer Engineering, Sahand University of Technology)
• Amin Abdollahi(Faculty of Polymer Engineering, Sahand University of Technology)