Preparation of epoxidized novolac resin nanocomposites: Physical and chemical incorporation of modified graphene oxide layers for improvement of thermal stability

Abstract

Graphene oxide (GO) modified with different functionalities was used in epoxidized novolac resin (ENR) matrix for increasing its thermal stability. Furfuryl alcohol moieties were firstly anchored to the edge of GO to yield GOFA. After that amine and epoxy functionalities were introduced onto the surface of GOFA layers using (3-aminopropyl)triethoxysilane and (3-glycidyloxypropyl) triethoxysilane, respectively to obtain GOFAA and GOFAG. Then, these three modified graphenes were incorporated into nanocomposite networks with ENR after using ethylenediamine as curing agent. It is expected that covalent bonding between GOFAA and GOFAG with ENR in the cured nanocomposites results in increased thermal degradation temperatures and also char residues. The results of Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and also X-ray diffraction confirmed successful functionalization of GO in three modified graphenes. Thermogravimetric analysis showed increased degradation temperatures and char residues for ENR nanocomposites with different modified graphenes. Physically-incorporated GOFA in ENR nanocomposite (GENH0.5) showed lower degradation temperature and char content (402.3 °C and 47.4%) compared with the chemically-incorporated GOFAA or GOFAG in ENR nanocomposites (412.4 °C and 60.2% for GENH0.5A and 438.1 °C and 53.4% for GENH0.5G). SEM and TEM images showed lots of creases in the layers after oxidation.