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Two different methods were used for preparation of novolac phenolic resin nanohybrids containing carbon nanotube and silica/siloxane moieties. Oxidized carbon nanotube was modified with furfuryl alcohol and 3-(trimethoxysilyl)propyl methacrylate (MPS) to obtain CNTFASi. Carbon nanotube xerogel (CNTFAX) was then obtained by incorporation of CNTFASi into silica/siloxane network by using tetraethyl orthosilicate (TEOS). The first nanohybrid was prepared by addition of CNTFAX into the novolac phenolic resin matrix. Incorporation of (3-glycidyloxypropyl) trimethoxysilane-modified novolac phenolic resin, CNTFASi, and TEOS into silica/siloxane network results in the second nanohybrid. These two types of nanohybrids were compared from the viewpoint of thermal properties. Successful modification of carbon nanotube and novolac phenolic resin was proved by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis results. Molar ratios of furfuryl alcohol in CNTFA and MPS in CNTFASi are 597 and 108 μmol g−1, respectively. Formation of silica/siloxane xerogel network in CNTFAX was evaluated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results showed that nanotubes with smooth surface are incorporated into the spongy silica/siloxane matrix. Char residue of CR is decreased from 58.2 to 50.6% by the addition of only 4 mass% of CNTFAX. Finally, char residue of 71.1% for the nanohybrid of modified novolac resin with 4 mass% of CNTFASi shows 12.8% increase in char residue with respect to the neat cured resin.

CNTCOOH was prepared from oxidation of carbon nanotube. Subsequently, CNTSi was prepared by grafting (3-glycidyloxypropyl) trimethoxysilane (GPTES) to the surface of CNTCOOH by a ring opening reaction of epoxy groups. Then, CNTA was obtained by formation of silicon oxide network between CNTSi and tetraethyl orthosilicate (TEOS). Finally, CNTA was used as an additive in novolac resin matrix to yield RCNTA composites with high carbon yield values. Additionally, modification of novolac resin by GPTES gives MR with silicon ethoxide moieties on its structure. Then, MRCNTA composites were obtained by formation of silica/siloxane network from MR, CNTSi, and TEOS. RCNTA composites were thermally compared with MRCNTA composites. Results from Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis showed that CNT and novolac resin were successfully modified. Aerogel formation was proved by Raman, X-ray diffraction, and scanning and transmission electron microscopies. BET shows that incorporation of CNT into the aerogel network results in lower cumulative pore volume value. The pore size of SA and CNTA ranges from 2 to about 100 nm which shows that both of them can be included in the mesoporous materials category. Finally, MRCNTA composites reached to the maximum increase of char yields; 11.94% increase of char yield was achieved by MRCNTA4 composite.

Graphene oxide (GO) modified with furfuryl alcohol and (3-aminopropyl) triethoxysilane (GOFASi) was used in two separate ways for preparation of novolac resin nanohybrids. In the first procedure, graphene-containing silica aerogel (GA) was obtained by incorporation of GOFASi into silica aerogel network using tetraethyl orthosilicate (TEOS). Then, GA was used as an additive in novolac resin matrix. In the second procedure, the synthesis of a hybrid novolac resin was accomplished by network formation via the reaction of GOFASi with (3-glycidyloxypropyl)trimethoxysilane-modified novolac resin and TEOS. The thermal stability and the carbon yield of the hybrid resins obtained by the two procedures were compared. Fourier transforms infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis showed that both GO and the novolac resin were successfully modified. Aerogel formation was proved by Raman, X-ray diffraction, N2 adsorption and desorption isotherms, and by scanning and transmission electron microscopies.

Graphene oxide (GO) was prepared via Hummers' method and reduced by hydrazine monohydrate to obtain rGO. GO and rGO nanosheets with different contents were used in in situ interfacial polymerization of 1,2-dichloromethane (EDC) and disodium tetrasulfide (Na2S4). The success of oxidation and reduction of nanosheets were confirmed by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray powder diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Proton nuclear magnetic resonance (1H NMR) was used to determine the molecular weights of polymers. Also, dispersion of nanosheets in polymeric matrix was studied by XRD and thermal stability and thermophysical properties of nanocomposites were investigated by TGA and differential scanning calorimetry (DSC). Results showed that incorporation of nanosheets leads to lower molecular weight of matrix polymer whereas reduced nanosheets were dispersed more appropriately in matrix. According to TGA results, dispersion of nanosheets and molecular weight of the matrix are prominent factors in thermal stability of nanocomposites. Also, all samples showed glass transition temperature (Tg) less than 0°C, a cold crystallization temperature (Tcc), and subsequent melting (Tm) affected by loading content of nanosheets. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

A “knotted approximation” (KA) is proposed in order to predict the Young’s modulus of blend-based polymer nanocomposites (BPNs). The BPN system is considered to have two fundamental constituents, a binary polymer blend and an effective phase (nanoparticle-containing phase). Therefore, the KA model was designed to combine the results of two different models which govern different hypothetical constituent elements of BPN systems. This was very helpful to enhance the accuracy of KA model by controlling parameters which affect each model. Furthermore, the application of different models was investigated to obtain the most efficient mathematical framework. Despite simple methodology of the KA model, the consistency of governing models on each constituent was considered as an important factor. Based on the wetting coefficient, the nanoparticles were considered to be in an individual phase of the binary polymer blend, so it could satisfy the presumptions of the effective phase. Considering the strong influences of nanoparticles on the percolation threshold of polymer phases, a general method was proposed to consider this important phenomenon. As a result, combining the fundamental concepts of KA constituent models enabled it to involve a wide range of critical parameters related to the BPN systems, e.g., morphology, random orientation of nanoparticles, nanoparticle/polymer interphase, phase inversion, polymer phase percolation threshold, etc. To evaluate the accuracy of KA model, different samples of polyamide/polyolefin elastomer/Cloisite 30B were prepared and subjected to stress–strain test in order to compare the predicted and actual values of BPNs Young’s modulus.

Carbon nanotube (CNT) was oxidized to obtain CNTCOOH. Then, furfuryl alcohol (FA) moieties were grafted to convex surface and end caps of CNTCOOH by an esterification reaction to yield CNTFA. CNTFA in three different contents was added into novolac resin matrix to improve its carbon yield value and thermal properties. Results from Fourier transform infrared, X-ray photoelectron, and Raman spectroscopies in addition to thermogravimetric analysis showed that CNT was successfully oxidized and modified with FA moieites. Morphological study and dispersion of nanotubes in the novolac resin matrix were studied by scanning and transmission electron microscopies and X-ray diffraction. FA graft content in CNTFA is calculated to be 8.2 %. Also, char value of the novolac resin was increased by 7.1 % by the addition of only 6 wt% of CNTFA.