Preparation of carbon nanotube-containing hybrid composites from epoxy, novolac, and epoxidized novolac resins using sol–gel method

Abstract

Three different hybrid composites were prepared from tetraethyl orthosilicate oligomer-modified epoxy resin (MER), (3-glycidyloxypropyl)trimethoxysilane-modified novolac resin (MNR), epoxidized novolac resin (ENR), and furfuryl alcohol and 3-(trimethoxysilyl)propyl methacrylate (MPS)-modified carbon nanotubes (CNTS) by combination of sol–gel method and curing reaction. The first hybrid composite (CMEMNH) was prepared from CNTS, MER, and MNR and curing of epoxy groups with ethylenediamine. The second hybrid composite (CENMNH) was prepared from CNTS, ENR, and MNR and subsequent curing of ENR with ethylenediamine. The third hybrid composite (CMENH) was prepared from CNTS and MER and curing of novolac resin with epoxy groups of MER. Finally, the three hybrid composites were thermally evaluated. Successful modification of CNTCOOH by furfuryl alcohol and MPS was confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy results. X-ray diffraction patterns for hybrid composites show a broad amorphous peak at diffraction angle of about 19.8° related to silica/siloxane domains. Thermogravimetric analysis results show that the higher char content (54.7) and the most increase in char residue (23.19%) are observed for the CENMNH composite with 4 mass% of CNTS. In the case of CMEMNH and CMENH composites, MER incorporation results in lower char residues. In most of the composites, the presence of CNTS and its incorporation into the hybrid network improve final thermal stability of the product. Scanning electron microscopy and transmission electron microscopy images show tubular structure of CNTS with smooth surface.