Multifunctional nanocomposites based on tetraethylenepentamine-modified graphene oxide/epoxy

Composites based on epoxy/graphene were investigated for thermal-mechanical performance. Initially, few-layer graphene oxide (GO) was modified with tetraethylenepentamine (GO-TEPA) in a reaction assisted by microwave radiation. GO and GO-TEPA samples were characterized for their structure and morphology. Composites containing 0.1, 0.3 and 0.5 wt.% of GO and GO-TEPA were prepared, and the effect of fillers on the morphology of cryofractured regions of epoxy matrix was observed through electron microscopy images. Dynamic mechanical thermal analysis (DMA) tests revealed increases of approximately 20 °C in glass transition. Moreover, when compared to neat polymer, composites containing 0.5 wt.% of GO-TEPA gained up to 103% in thermal conductivity (obtained by flash laser). Finally, nanoindentation analyses showed increases of 72% in Young's modulus and 143% in hardness for the same sample. The system is characterized as multifunctional nanocomposites because of the simultaneous gains in thermal and mechanical properties. The best results of the multifunctional composites were strongly associated with the chemical modification of the GO by TEPA.     

Synergistic modification by mercapto hyperbranched polysiloxane and functionalized graphene oxide on the surface of aramid fiber

With the purpose of improving the interfacial properties of aramid fibers reinforced rubber composites and enhancing the tensile strength of aramid fibers simultaneously, mercapto hyperbranched polysiloxane (HPSi) and functionalized graphene oxide (GO) were used to modify the surface of aramid fibers. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and other characterization methods were performed to confirm the process of synergistic modification. Judging from the results of mechanical property tests, it could be acquired that the tensile strength of modified aramid fiber was increased by 16.8%, which could be ascribed to the wrapping effect of GO sheets. The interfacial properties were assessed by the pull-out tests of composites, and the results showed that the maximum pull-out force after synergistic surface modification was increased by 99.3%, which could be mainly related to additive reaction between double bonds and mercapto groups and the promotion of surface energy. More critically, during pull-out test, aramid fiber bundles might bring a part of shear stress into the grafted GO sheets, namely, GO sheets could convert fracture energy into interfacial energy, which would improve interfacial properties dramatically.     

Simultaneous functionalization and reduction of graphene oxide with polyetheramine and its electrically conductive epoxy nanocomposites

Simultaneous functionalization and reduction of graphene oxide(GO) is realized by refluxing of GO suspension with polyetheramine(D2000) followed by thermal treatment at 120 °C. Compared to GO, the D2000-treated GO(GOD2000) becomes hydrophobic, thermally stable and highly conductive with an electrical conductivity of 11 S/m, which is almost 8 orders of magnitude higher than that of GO. Due to the high conductivity and improved dispersion of GO-D2000, its epoxy nanocomposites exhibit a sharp transition from electrically insulating to conducting with a low percolation threshold of 0.71 vol%. With 3.6 wt% GO-D2000, the glass transition temperature of the epoxy nanocomposite is 27 K higher than that of neat epoxy.     

Dispersion of graphene oxide and its flame retardancy effect on epoxy nanocomposites

Graphene oxide was prepared by ultrasonication of completely oxidized graphite and used to improve the flame retardancy of epoxy.The epoxy/graphene oxide nanocomposite was studied in terms of exfoliation/dispersion,thermal stability and flame retardancy.X-ray diffraction and transmission electron microscopy confirmed the exfoliation of the graphene oxide nanosheets in epoxy matrix.Cone calorimeter measurements showed that the time to ignition of the epoxy/graphene oxide nanocomposite was longer than that of neat epoxy.The heat release rate curve of the nanocomposite was broadened compared to that of neat epoxy and the peak heat release rate decreased as well.     

Aptamer functionalized magnetic graphene oxide nanocomposites for highly selective capture of histones

The binding coverage of aptamer was an important restricted factor for aptamer‐based affinity enrichment strategy for capturing target molecules. Herein, we designed and prepared aptamer functionalized graphene oxide based nanocomposites (GO/NH₂‐NTA/Fe₃O₄/PEI/Au), and the coverage density of aptamer was high to 33.1 nmol/mg. The high aptamer coverage density was contributed to the large surface area of graphene oxide. The successive modification of Nα,Nα‐Bis(carboxymethyl)‐L‐lysine, magnetic nanoparticles, polyethylenimine, and Au nanoparticles ensured the histone purification with fast speed and high purity. Histones could be captured rapidly and specifically from nucleoproteins by our aptamer based purification strategy, while traditional acid‐extraction could not specifically enrich histones. Compared with traditional acid‐extraction method, rapid and efficient discovery of histones and their post‐translational modifications, such as several kinds of methylation at H3.1K9 and H3.1K27, were achieved confidently. It demonstrated that our aptamer functionalized magnetic graphene oxide nanocomposites have a great potential for histone analysis.     

Synthesis of the polyethylene glycol solid-solid phase change materials with a functionalized graphene oxide for thermal energy storage

Polyethylene glycol (PEG) as a phase change material possesses three obstacles, such as leakage, low thermal conductivity and low thermal stability. A novel solid-solid phase change material (PCM) based on functionalized graphene oxide (GO), Polyethylene glycol (PEG) was prepared, and the three obstacles of PEG as a PCM was solved in one and the same material. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman and Transmission electron microscope (TEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and thermogravimetric analysis/infrared spectrometry (TG-IR) were used to study the properties of supporting material and composite PCM (CPCM). The results indicated that the PEG was grafted on the surface of the supporting material; Compared with pure PEG, the latent heat of CPCM with 9.6 wt% supporting material decreased only 5.3%, however, the thermal conductivity of CPCM increased 111% and the heat peak release rate of CPCM decreased 33.4%.     

Enhancement of mechanical properties of natural rubber with maleic anhydride grafted liquid polybutadiene functionalized graphene oxide

An effective procedure has been developed to synthesize the functionalized graphene oxide grafted by maleic anhydride grafted liquid polybutadiene(MLPB-GO). Fourier transform spectroscopy and X-ray photoelectron spectroscopy indicate the successful functionalization of GO. The NR/MLPB-GO composites were then prepared by the co-coagulation process. The results show that the mechanical properties of NR/MLPB-GO composites are obviously superior to those of NR/GO composites and neat NR. Compared with neat NR, the tensile strength, modulus at 300% strain and tear strength of NR composite containing 2.12 phr MLPB-GO are significantly increased by 40.5%, 109.1% and 85.0%, respectively. Dynamic mechanical analysis results show that 84% increase in storage modulus and 2.9 K enhancement in the glass transition temperature of the composite have been achieved with the incorporation of 2.12 phr MLPB-GO into NR. The good dispersion of GO and the strong interface interaction in the composites are responsible for the unprecedented reinforcing efficiency of MLPB-GO towards NR.     

4-Mercaptophenylboronic acid functionalized graphene oxide composites: Preparation,characterization and selective enrichment of glycopeptides

Selective enrichment and isolation of glycopeptides from complex biological samples was indispensable for mass spectrometry (MS)-based glycoproteomics, however, it remained a great challenge due to the low abundance of glycoproteins and the ion suppression of non-glycopeptides. In this work, 4-mercaptophenylboronic acid functionalized graphene oxide composites were synthesized via loading gold nanoparticles on polyethylenimine modified graphene oxide surface, followed by 4-mercaptophenylboronic acid immobilization by the formation of Au–S bonding (denoted as GO/PEI/Au/4-MPB composites). The composites showed highly specific and efficient capture of glycopeptides due to their excellent hydrophilicity and abundant boronic acid groups. The composites could selectively capture the glycopeptides from the mixture of glycopeptides and nonglycopeptides, even when the amounts of non-glycopeptides were 100 times more than glycopeptides. Compared with commercial meta-amino phenylboronic acid agarose, the composites showed better selectivity when the sample was decreased to 10 ng. These results clearly verified that the GO/PEI/Au/4-MPB composites might be a promising material for glycoproteomics analysis.     

Preparation of quaternarized N-halamine-grafted graphene oxide nanocomposites and synergetic antibacterial properties

At present, frequent outbreaks of bacteria and viruses have seriously affected people's normal lives. Therefore, the study of broad-spectrum antibacterial nanocomposites is very promising. However, most antibacterial materials have some disadvantages, such as single bactericidal mechanisms and unrepeatable use. Based on the current situation, a kind of nanocomposite with three structures of graphene oxide (GO), quaternary ammonium salt (QAs) and N-halamine was prepared, which showed synergistic effect to improve antibacterial activity and combined with a variety of sterilization mechanisms. Meanwhile, GO can provide richer ways of sterilization and high specific surface area, which is conducive to the grafting of quaternarized N-halamine. The advantages of physical sterilization of GO, charge adsorption of QAs, reuse of N-halamine and efficient sterilization are fully utilized. The results showed that the quaternarized N-halamine-grafted GO was obtained successfully. GO grafted with quaternarized N-halamine polymer showed strong speedy bactericidal activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) (99%). It had good storage and regeneration properties.     

Synergistic effects of functionalized graphene and functionalized multi-walled carbon nanotubes on the electrical and mechanical properties of poly(ether sulfone) composites

Mixed fillers composed of functionalized graphene (f-G) and functionalized multi-walled carbon nanotubes (f-CNTs) (f-G-f-CNTs) were prepared and their synergistic effects in terms of enhancing the electrical conductivity and tensile modulus of poly(ether sulfone) (PES) composites were investigated. The results indicate that the electrical conductivity of the 5 wt% f-G-f-CNTs(W_f-G/W_f-CNTs = 1:1)/PES composite was 2.2 times higher than that of the 5 wt% f-G/PES composite and 8.9 times higher than that of the 5 wt% f-CNTs/PES composite. Moreover, the tensile modulus of the 5 wt% f-G-f-CNTs(W_f-G/W_f-CNTs = 1:1)/PES composite relative to that of the 5 wt% f-G/PES composite and 5 wt% f-CNTs/PES composite increased by 16.5% and 50.6%, respectively. Additionally, enhancements in the electrical conductivity and tensile modulus of the PES composite depended on the weight ratio of f-G and f-CNTs in the mixed fillers. The electrical conductivity and tensile modulus exhibited maximum values when the weight ratios of f-G and f-CNTs were 1:3 and 1:1, respectively. When the weight ratio of f-G and f-CNTs was fixed at 1:1, the f-G-f-CNTs(W_f-G/W_f-CNTs = 1:1)/PES composite showed a percolation threshold of 0.22 vol%, much lower than that of the f-G/PES composite.     

Viscoelastic response and interlaminar delamination resistance of epoxy/glass fiber/functionalized graphene oxide multi-scale composites

Graphene oxide (GO) was functionalized using three different diamines, namely ethylenediamine (EDA), 4,4′-diaminodiphenyl sulfone (DDS) and p-phenylenediamine (PPD) to reinforce an epoxy/glass fiber (EP/GF) composite laminate, with the aim of improving the overall composite mechanical performance. Different mechanical characterization techniques were used to determine the mechanical performance, including: tensile stress strain, double cantilever beam (DCB) mode-I fracture toughness and dynamic mechanical thermal analysis (DMTA). Scanning electron microscopy (SEM) was used to support the results and conclusions. The results demonstrated remarkable enhancements in the mechanical performance of EP/GF composite laminates by incorporation of functionalized graphene oxide (FGO) nanofiller, whilst the mechanical performance of the GO reinforced composite only improved marginally. Finally, the mechanical performance of the EP/GF/FGO multi-scale composites was found to be dependent on the type of FGO functional groups; of which EDA exhibited the highest performance. These investigations confirmed that the EDA-FGO-reinforced EP/GF composites possess excellent potential to be used as multifunctional engineering materials in industrial applications.     

Enhanced mechanical properties of carbon fiber composites by grafting different structural poly(amido amine) onto fiber surface

The mechanical properties of carbon fiber composites depend on the interfacial strength between fiber and epoxy matrix. Different poly (amido amine) (PAMAM) dendrimers were grafted onto carbon fiber to improve the interfacial strength of the resulting composites. Functional groups on the carbon fiber surface were examined by X-ray photoelectron spectroscopy. The surface morphology of the resulting materials was characterized by scanning electron microscopy and atomic force microscope. The characterization results revealed that PAMAM dendrimers were chemically grafted onto the surface of carbon fiber. More importantly, the mechanical properties of the resulting composites were enhanced owing to the presence of sufficient functional groups on the carbon fiber surface. In addition, after PAMAM containing chair conformations were grafted, the interlaminar shear strength had the highest increase of 53.13%, higher than that of the fiber grafted with PAMAM containing terminated linear amine. This work provides an alternative approach to enhance the mechanical properties of fiber composites by controlling the interface between fiber and epoxy matrix.     

Investigation into effect of the graphene oxide addition on the mechanical properties of the fiber metal laminates

Fiber Metal Laminates (FMLs) is developing very fast with the both features of resin-based composite and metal and its property can be improved by mixing nano-scale particles as FMLs-Nano. Based on the different mixing volume fractions, this paper investigated the effect of Graphene Oxide (GO) on the mechanical properties of the FMLs with carbon fiber used, including tensile, flexural and interface shear behaviors. The interface strengthening mechanism of GO as significant filler for enhancing the carbon woven fabric based FMLs' was explored. To encourage the application range of FMLs-Nano in the fields of aircraft, aerospace and automotive etc. to form the complicated components. It was observed that the FMLs with GO (FMLs-GO) has the better tensile performance than the FMLs without GO and the Young's modulus and tensile strength of the FMLs-GO are increased by 13.5% and 11.7%, respectively. Especially, the flexural and interface shear strength can be increased up to 134.0% and 150.4% compared to the pure FMLs and the improvement mechanism was investigated mechanically and observed with scanned micrograph. This paper also provides a fundamental reference for improving the interfacial performance of different layers of FMLs-GO by using the normal preparation condition.     

Synergetic effects of carbon nanotube and graphene addition on thermo-mechanical properties and vibrational behavior of twill carbon fiber reinforced polymer composites

The effect of carbon based nanoparticles addition, such as Multi Wall Carbon Nanotube (MWCNTs) and Graphene Nano Platelets (GNPs), on mechanical and thermal properties of Carbon Fiber Reinforced Polymer Composites (CFRPs) was experimentally investigated. 2/2 twill woven carbon textile was used to fabricate the CFRP samples. The main aim of this study was to improve the weak interface behavior of carbon fibers with polymers by using its own nanoparticles in the structure of CFRPs. The obtained results from thermal tests, such as storage modulus, loss factors, glass transition temperature and loss weight percentage, were compared to reveal the influence of nanoparticles in the structure of CFRPs. The effects of MWCNTs and GNPs addition on natural frequency and damping ratio of multi scale composites were studied by using vibrational tests. The effect of nanoparticles addition on water uptake nature of CFRPs was investigated by hydrophobicity test. The results showed that MWCNT and GNP nanoparticles improved the mechanical and dynamic behavior of CFRP composite materials by improving the modulus of elasticity, tensile strength, flexural modulus, strength, ILSS, critical buckling load, and natural frequency. Furthermore, the thermal characteristics of CFRPs, such as storage modulus, thermal stability and thermal conductivity, were improved by the addition of carbon based nanoparticles. It was observed that the MWCNT multi scale composites had better performance than the GNP. According to the results of hydrophobicity test, the addition of MWCNTs enhanced the hydrophobic nature while the GNPs increased the hydrophilic nature of CFRPs.     

Physical and mechanical properties of graphene oxide/polyethersulfone nanocomposites

The aim of this study was to investigate physical and mechanical properties of graphene oxide (GO)/polyethersulfone (PES) nanocomposite films. The films were produced by solution casting method. The mechanical properties of composite films were evaluated by tensile test. A significant enhancement in the mechanical properties of neat PES films was obtained incorporating a small amount of GO loading (0.05–1 wt.%). The highest tensile strength was observed at 1 wt.% of GO. Comparisons were made between experimental data and the Halpin–Tsai model predictions for the tensile strength and modulus of GO/PES composites. The effect of an orientation factor on model predictions was also acquired. The hydrophilicity of the nanocomposite was evaluated by assessing contact angle and enhanced wet ability of the films was obtained with increasing the amount of GO up to 1%. The morphology of the nanocomposites was investigated using scanning electron microscopy and transmission electron microscopy and the results revealed a good dispersion of GO in the PES matrix. The thermal behavior of the composite was also studied. Thermal stability of composites was increased by adding the GO. Copyright © 2013 John Wiley & Sons, Ltd.     

Ionic liquid functionalized graphene oxide for enhancement of styrene‐butadiene rubber nanocomposites

Ionic liquid 1‐allyl‐3‐methyl‐imidazolium chloride (AMICl) is used to fine‐tune the surface properties of graphene oxide (GO) sheets for fabricating ionic liquid functionalized GO (GO‐IL)/styrene‐butadiene rubber (SBR) nanocomposites. The morphology and structure of GO‐IL are characterized using atomic force microscope, X‐ray diffraction, differential scanning calorimetry, X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, UV‐vis spectra and Raman spectra. The interaction between GO and AMICl molecules as well as the effects of GO‐IL on the mechanical properties, thermal conductivity and solvent resistance of SBR are thoroughly studied. It is found that AMICl molecules can interact with GO via the combination of hydrogen bond and cation–π interaction. GO‐IL can be well‐dispersed in the SBR matrix, as confirmed by X‐ray diffraction and scanning electron microscope. Therefore, the SBR nanocomposites incorporating GO‐IL exhibit greatly enhanced performance. The tensile strength, tear strength, thermal conductivity and solvent resistance of GO‐IL/SBR nanocomposite with 5 parts per hundred rubber GO‐IL are increased by 505, 362, 34 and 31%, respectively, compared with neat SBR. This method provides a new insight into the fabrication of multifunctional GO‐based rubber composites. Copyright © 2016 John Wiley & Sons, Ltd.     

Facile regulation of glutaraldehyde-modified graphene oxide for preparing free-standing papers and nanocomposite films

Colloidal suspensions of glutaraldehyde (GA) crosslinked or grafted graphene oxide (GO) sheets were fabricated by simply tailoring the feed sequence. The different structures were confirmed by Fourier transform infrared spectra and X-ray diffraction. As demonstration of the utilities, the different colloidal suspensions were used to prepare free-standing papers by flow-directed filtration and poly(vinyl alcohol) (PVA)-based nanocomposite films by casting. Free-standing papers from GA crosslinked GO sheets exhibited better mechanical properties than unmodified GO paper, while nanocomposite films from GA grafted GO exhibit higher tensile strength and Young’s modulus.     

Biodegradable graphene oxide nanosheets/poly-(butylene adipate-co-terephthalate) nanocomposite film with enhanced gas and water vapor barrier properties

Poly-(butylene adipate-co-terephthalate) (PBAT) has captured significant interest by dint of its biodegradability, superb ductility, promising processing properties and good final properties, but the insufficient barrier performance limits its application, especially in packaging field. In the present work, improved barrier properties of PBAT films were obtained by introducing an extremely low amount of graphene oxide nanosheets (GONS). O₂ and water vapor permeability coefficients were decreased by more than 70% and 36% at the GONS loading of 0.35 vol%, respectively. The enhanced barrier performance was ascribed to the outstanding impermeability and well dispersion of GONS as well as the strong interfacial adhesion between GONS and PBAT matrix. Furthermore, tensile strength and Young's modulus of GONS/PBAT nanocomposite rise up to 27.8 MPa and 72.2 MPa from 24.6 MPa to 58.5 MPa of neat PBAT, respectively, showing a prominent increase of mechanical properties compared to neat PBAT. The incorporation of GONS also endowed PBAT matrix with an excellent thermal stability. These findings provide a significant guidance for fabricating high barrier films on a large scale.     

Preparation and thermal properties of graphene oxide/main chain benzoxazine polymer

Graphene oxide/polybenzoxazine nanocomposites are prepared using main chain benzoxazine polymer (MCBP) via a solvent casting method from different organic solvents. The addition of graphene oxide to the polymeric matrix leads to a gradual decrease in the glass transition temperature of the polymeric matrix. This drop is attributed to the reactive nature of graphene oxide, which undergoes exothermic thermal de-oxygenation before the onset of polybenzoxazine ring opening polymerization upon curing of the nanocomposites. Additionally, it is reported that the glass transition of polybenzoxazine films cast from different solvents depends on the nature of the solvent.     

Influence of surface properties of graphene oxide/carbon fiber hybrid fiber by oxidative treatments combined with electrophoretic deposition

An effective way to prepare graphene oxide/carbon fiber hybrid fiber was proposed by the treatment with hydrogen peroxide and concentrated nitric acid combined with electrophoretic deposition process. Surface functional group, surface roughness, and surface morphologies of carbon fibers were examined by Fourier transform infrared spectrometer, atomic force microscopy, and scanning electron microscopy. Results showed that a uniform and thick graphene oxide films were constructed on the surface of carbon fiber. Deposition density increased by introduction of pretreatment of the carbon fiber in the electrophoretic deposition process has been shown as a possible method. Dynamic contact angle analysis results indicated that the deposition of graphene oxide significantly improved surface free energy of carbon fiber by increasing surface area and polar groups. The introduction of graphene oxide in the carbon fiber‐reinforced epoxy composites results in a 55.6% enhancement in the interfacial shear strength and confirms the remarkable improvement in the interfacial adhesion strength of the composites, and the fracture mechanism was also analyzed. Copyright © 2016 John Wiley & Sons, Ltd.