Preparation of hybrid composites based on epoxy, novolac, and epoxidized novolac resins and silica nanoparticles with high char residue by sol-gel method

A facile method was developed for preparation of three hybrid composites by using tetraethyl orthosilicate oligomer-modified epoxy resin (MER), (3-glycidyloxypropyl) trimethoxysilane-modified novolac resin (MNR), epoxidized novolac resin (ENR), and silica nanoparticles (SiO2). Accordingly, the first class of composites was prepared from MER and SiO2. The second class of composites was prepared from MER, MNR, and SiO2. And the third class of composites was prepared from silica MNR, ENR, and nanoparticles. All the modified resins and their composites were characterized by Fourier-transform infrared spectroscopy and their thermal behavior was investigated by thermo gravimetric analysis. The obtained thermograms showed that thermal stability of hybrid composites were controlled by the amount of SiO2 and type of resins. Char yield of epoxy resin was increased significantly by formation of hybrid composites. The second class of composites showed higher char yields in comparison with the first class (52.1 compared with 23.2% for 8 wt% of SiO2). Incorporation of ENR instead of MER in the third class composites resulted in much more char residues of 60.2 and 60.6% for 4 and 8 wt% of SiO2. Therefore, third class composite with 8 wt% of SiO2 exhibited the highest char yield. Scanning electron and transmission electron microscopies were used to study the morphology and dimension of SiO2. POLYM. COMPOS., 39:E2316-E2323, 2018. (c) 2017 Society of Plastics Engineers