Low Graphene Loading Research Articles

Development of multifunctional nanocomposites with 3-D printing additive manufacturing and low graphene loading

Fused filament fabrication (FFF) or fused deposition modeling is an additive manufacturing (AM) process commonly used for geometric modeling and rapid prototyping of parts called three-dimensional (3-D) printing. Commonly used thermoplastic materials in FFF 3-D printing AM are acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), and polybutylene terephthalate (PBT). However, these materials exhibit relatively low strength and toughness. Therefore, it is desirable to improve various properties of thermoplastics in 3-D printing AM by employing nanotechnology. The combination of 3-D printing and nanotechnology opens new venues for the manufacture of 3-D engineered materials with optimized properties and multifunctionality (e.g. mechanical, electrical, and thermal properties). Hence, in this work, the multifunctional property improvement effects of graphene oxide (GO) on thermoplastic materials suitable for 3-D printing AM are investigated. Low loading of GO with carboxyl and hydroxyl surface functional groups is incorporated into thermoplastic materials suitable for 3-D printing AM by a special mixing technique. ABS is chosen in this study due to its availability. Graphene nanosheets are employed to improve the properties of the developed nanocomposites by 3-D printing AM. GO is chosen to improve the dispersion of graphene nanosheets into the thermoplastic system to increase their interfacial adhesion. A multifunctional property improvement is observed in the developed nanocomposite with less than 0.1 wt% GO. Employing ASTM standard tests, it was found that at a very small loading of 0.06% by weight, GO could improve the properties of the thermoplastic in terms of strength, strain-to-failure, and toughness, while maintaining the stiffness, rendering the developed nanocomposites suitable for various applications of static and dynamic loading. GOs are now commercially available at low prices. At such low loadings, these graphene-type materials become economically feasible components of nanocomposites.

Mechanical and dielectric properties of graphene incorporated polypropylene nanocomposites using polypropylene-graft-maleic anhydride as a compatibilizer

To achieve uniform dispersion of graphene in polypropylene, polypropylene-graft-maleic anhydride (PP-g-MA) as compatibilizer was compounded with graphene to obtain masterbatch, and then melt blended with polypropylene using a micro-compounder. Raman study showed the strong interfacial interaction between the surface of functionalized graphene sheets (FGS) and the compatibilizer, while morphologic study indicated the homogeneous dispersion of graphene in polypropylene. Remarkable enhancements in mechanical, thermal and dielectric properties were obtained at low graphene loading. At an effective graphene content of 1.5 wt%, the tensile strength and storage modulus of polypropylene increased by 18% and 33%, respectively. The electrical percolation threshold of the nanocomposites is about 0.55 vol%, which is lower than most of previously reported polypropylene composites prepared by similar melt processing. Near the percolation threshold (0.535 vol% graphene), the dielectric permittivity increased to 15.2 and the loss tangent was kept as low as 0.20 at 103 Hz.

Graphene-induced enhancement of water vapor barrier in polymer nanocomposites

Abstract Reduction in water vapor permeability is both fundamentally important and a practical necessity in the polymer industry for packaging and protective applications. The barrier of polymers is significantly improved by inclusion of impermeable lamellar fillers, increasing the diffusion path of gas or water vapor molecules. The most common “barrier-modifier” for polymers is clay, which is less effective for reducing water vapor permeability since it absorbs water, swells and also degrades other properties (e.g., mechanical strength). In this study we focus on graphene as the barrier filler in polyurethane, examining the influence of its lateral size and concentration on both water vapor permeability and the mechanical properties. We demonstrated optimal barrier and mechanical enhancements at low graphene loading of 2 and 1 wt%, respectively. We tested few lateral dimension of graphene and found that the larger size (25 μm) exhibited an optimal barrier enhancement (50% reduction). In addition we found correlation between the onset of the barrier and an increase in the polymer viscosity.

Graphene-based Polymer Nanocomposites: Recent Advances and Still Open Challenges

Background: From its appearance in the scientific literature, graphene has received much interest, first from the scientific community and then, after the scale-up of the methods suitable for its production, from the industrial world. Nowadays, this nanofiller has to be considered as one of the most promising and performing materials ever discovered: in fact, it is deserving application in different fields, including nanoelectronics, quantum physics, catalysis, energy research and engineering of nanocomposites and biomaterials. The remarkable growth in science, graphene underwent during the last 15 years, is strictly connected to its peculiarities, such as high Young’s modulus, high fracture strength, remarkable thermal and electrical conductivity, large specific surface area, high charge carrier mobility and also biocompatibility. At present, one of the application fields where graphene is gaining a lot of success refers to the fabrication of polymer composites on a commercial scale and low/affordable cost, including both thermoplastic and thermosetting host matrices. These composites do exploit the homogeneous dispersion level of the nanofiller within the polymer matrix, mainly for enhancing the electrical and thermal conductivity of this latter, as well as its mechanical properties, in a remarkable way, even in the presence of very low graphene loadings. In addition, the obtained nanocomposites usually show higher thermal stability with respect to the unfilled polymer matrix. At present, there are about six main areas related to emerging applications for this nanofiller, including displays/screens, biomedical devices, memory chips, fuel cells/batteries, inks, coatings and, from an overall point of view, new smart materials. Keywords: Exfoliation, graphene, graphene oxide, graphene-based composites, reduced graphene oxide, thermoplastic matrices, thermosetting matrices.

Roles of cobalt doping on ethanol-sensing mechanisms of flame-spray-made SnO2 nanoparticles−electrolytically exfoliated graphene interfaces

In this work, the roles of cobalt (Co) and electrolytically exfoliated graphene additives on ethanol gas-sensing properties of flame-spray-made SnO2 nanoparticles were systematically studied. Structural characterizations indicated that Co dopants formed solid solution with SnO2 nanoparticles while multilayer graphene sheets were well dispersed within the Co-doped SnO2 matrix at low graphene loading contents. The sensing films were fabricated by a spin coating process and tested towards 50–1000ppm ethanol at 150–400°C. It was found that the response to 1000ppm ethanol at the optimal working temperature of 350°C was enhanced from 91 to 292 and to 803 by 0.5wt% graphene loading and 0.5wt% Co-doping, respectively. The combination of Co-doping and graphene loading with the same concentration of 0.5wt% led to a synergistic enhancement of ethanol response to 2147 at 1000ppm with a short response time of ∼0.9s and fast recovery stabilization at 350°C, proving the significance of dopant on the gas-sensing performances of graphene/SnO2 composites. Furthermore, the optimal sensor exhibited high ethanol selectivity against C3H6O, NO2, H2S, H2, CH4 and humidity. The mechanisms for the ethanol response enhancement were proposed on the basis of combinative effects of catalytic substitutional p-type Co dopants and active graphene−Co-doped SnO2 M-S junctions with highly accessible surface area of micropores and mesopores in the composites. Therefore, the graphene loaded Co-doped SnO2 sensor is highly potential for responsive and selective detection of ethanol vapor at ppm levels and may be practically useful for drunken driving applications.

Performance evaluation of polysulfone/graphene nanocomposites

Abstract The present work focuses on the performance and properties of organomodified graphene nanoplatelet filled polysulfone nanocomposites prepared by solution casting. Morphology of the nanocomposites was investigated using atomic force microscopy and transmission electron microscopy. Contact angle measurements showed significantly increased hydrophobicity of the nanocomposites relative to the neat polymer. Mechanical properties of the nanocomposites showed marked improvement at low graphene loadings. Thermal properties measured using thermogravimetric analysis showed that the incorporation of graphene increased the thermal stability and the char yield of the nanocomposites. After immersing the samples in various solvents, the changes in weight and mechanical property were evaluated and the aging performance was found to be improved. The prepared polysulfone nanocomposites with desired hydrophobic, thermal, mechanical and barrier properties are usable for high performance applications.

Mechanical reinforcement of graphene/poly(vinyl chloride) composites prepared by combining the in-situ suspension polymerization and melt-mixing methods

Abstract In order to obtain uniform dispersion of graphene and significant mechanical reinforcement of graphene filled poly(vinyl chloride) (PVC) composites, we used in-situ suspension polymerization to obtain graphene/PVC compounded resins with uniform dispersion of graphene, and subsequently prepared graphene/PVC composites using conventional melt-mixing technique. The microstructure, graphene dispersion, mechanical and thermal properties of the nanocomposites were investigated in detail. We found that the combination of in-situ polymerization and melt-mixing was effective in obtaining graphene/PVC composites with uniform graphene dispersion and significant mechanical reinforcement. The tensile strength, impact toughness, and thermal stability of the nanocomposites were greatly improved even at an extremely low graphene loading (0.3 wt%), which is mainly attributed to the uniform dispersion of graphene and strong graphene-PVC interactions. By virtue of their excellent mechanical properties and easy production, the graphene/PVC composites have great potential to be used as high-performance composites in many fields.

Thermally Annealed Anisotropic Graphene Aerogels and Their Electrically Conductive Epoxy Composites with Excellent Electromagnetic Interference Shielding Efficiencies.

Dispersion and spatial distribution of graphene sheets play crucial roles in tailoring mechanical and functional properties of their polymer composites. Anisotropic graphene aerogels (AGAs) with highly aligned graphene networks are prepared by a directional-freezing followed by freeze-drying process and exhibit different microstructures and performances along the axial (freezing direction) and radial (perpendicular to the axial direction) directions. Thermal annealing at 1300 °C significantly enhances the quality of both AGAs and conventional graphene aerogels (GAs). The aligned graphene/epoxy composites show highly anisotropic mechanical and electrical properties and excellent electromagnetic interference (EMI) shielding efficiencies at very low graphene loadings. Compared to the epoxy composite with 0.8 wt % thermally annealed GAs (TGAs) with an EMI shielding effectiveness of 27 dB, the aligned graphene/epoxy composite with 0.8 wt % thermally treated AGAs (TAGAs) has an enhanced EMI shielding effectiveness of 32 dB along the radial direction with a slightly decreased shielding effectiveness of 25 dB along the axial direction. With 0.2 wt % TAGA, its epoxy composite exhibits a shielding effectiveness of 25 dB along the radial direction, which meets the requirement of ∼20 dB for practical EMI shielding applications.

Thermal stability and mechanical properties of solution mixing–processed co-polyamide–graphene composites at extremely low graphene loading

To enhance the thermal stability and mechanical properties of co-polyamide (CO-PA), a sequence of nanocomposites based upon CO-PA and shear exfoliation graphene (SEG) were prepared via a simple solution mixing method. The graphene used as nanofiller was fabricated by shear exfoliation in aqueous phase and is free of basal-plane defects. Atomic force microscopy and scanning electron microscopy revealed that the graphene fabricated is few-layer graphene rather than solely monolayer graphene. X-ray diffraction and polarizing microscope indicated that SEG layers could change the crystallization behavior of the nanocomposites and conduce to the crystal form transformation. The CO-PA/SEG nanocomposites were found to be of outstanding thermal stability and mechanical properties at extremely a low graphene loading as opposed to neat CO-PA. In detail, at a graphene load of 0.05 wt%, the nanocomposites present 106.5, 56.1, and 33.7% enhancement in tensile strength, yield strength, and elongation at break compared to pristine CO-PA, respectively. Besides, thermal degradation temperatures at 50% weight loss of the nanocomposites is about 19°C higher than that of CO-PA when the SEG content is 0.15 wt%; the thermal degradation temperature at maximum weight loss rate of the nanocomposites is 25°C higher than that of CO-PA when the content of SEG is 0.20 wt%. All these enhancements of the nanocomposites were ascribed to the defect-free graphene, its superior thermal and mechanical properties, and its well exfoliation and dispersion in CO-PA matrix.

Strain Sensing Polymer Nanocomposites at Ultralow Graphene Loading Level

An electrically conductive ultralow percolation threshold of 0.1 wt% graphene was observed in the thermoplastic polyurethane (TPU) nanocomposites. The homogeneously dispersed graphene effectively enhanced the mechanical properties of the TPU significantly at a low graphene loading of 0.2 wt%. These nanocomposites were subjected to cyclic loading to investigate the influences of graphene loading, strain amplitude and strain rate on the strain sensing performances. The two dimensional graphene and flexible TPU matrix were found to endow these nanocomposites with wide range of strain sensitivity (gauge factor ranging from 0.78 for TPU with 0.6 wt% graphene at the strain rate of 0.1 min-1 to 17.7 for TPU with 0.2 wt% graphene at the strain rate of 0.3 min-1) and good sensing stability for different strain patterns. In addition, these nanocomposites demonstrated good recoverability and reproducibility after stabilization by cyclic loading. An analytical model based on tunneling theory was used to simulate the resistance response to strain under different strain rates. This study provides a guideline for the fabrication of graphene based polymer strain sensors. Experimental The graphene/TPU nanocomposites were fabricated by co-coagulation plus compression molding technique1. Briefly, 2.0 g TPU was dissolved in 50 mL DMF at 40 °C by vigorously stirring for 30 min. The required amount of aqueous graphene dispersion was mixed with 15 mL DMF and treated under ultrasonication for 10 min to disperse the graphene homogenously. Subsequently, the TPU/DMF and graphene/DMF were mixed together and sonicated for additional 30 min. The mixture was then added dropwise into 300 mL methanol under strongly stirring to obtain the flocculate of graphene/TPU. The obtained flocculate was filtered, dried at 80 °C under vacuum for 20 h, and hot pressed at 210 °C for 10 min under a pressure of 15 MPa. The thickness of the nanocomposites sample was 0.5 mm. The neat TPU control sample was also fabricated in the same manner for comparison. The obtained nanocomposites were denoted as TPU-xG, where x represents the mass loading of graphene, G is the abbreviation of graphene. For example, TPU-0.2G represents the TPU/graphene nanocomposites containing 0.2 wt% graphene Results and Discussion The SEM and TEM of graphene demonstrated the full exfoliation of graphene after the ultrasonic dispersion in DMF. Significant enhancement of mechanical properties of graphene/TPU nanocomposites was obtained due to the good interfacial interaction between graphene and TPU. The XRD, SEM and TEM of graphene/TPU nanocomposites showed homogeneous dispersion of graphene in TPU matrix2, and an ultralow percolation threshold was obtained. Strain sensing behaviors of the nanocomposites were conducted under different graphene loadings, strain amplitudes and strain rates, good discernment, sensitivity and sensing stability were obtained. All of these are benefited from the two dimensional graphene and good flexibility of TPU3. Conclusion Graphene/TPU nanocomposites with an ultralow percolation threshold of 0.1 wt% graphene were successfully prepared by co-coagulation plus compression molding technique. The H-bonding interaction between graphene sheets and TPU was confirmed from FT-IR. Graphene was distributed in the TPU matrix homogeneously and the mechanical property of the nanocomposites was enhanced significantly. The nanocomposites exhibited good sensitivity and sensing stability for different strain patterns, showing good discernment in strain sensing. Good recoverability and reproducibility were also obtained after stabilization by cyclic loading. The change of the number of conductive pathways and tunneling distance were responsible for the resistance-strain sensing behaviors under different strain rates according to the fitting results. Due to the fascinating strain sensing behaviors, the nanocomposites have great potential for applications as strain sensors to meet various demands in detecting various external environment stimuli4. Acknowledgments The financial supports from National Natural Science Foundation of China (Contract Number: 11572290, U1204507), and the University of Tennessee Knoxville are kindly acknowledged. Figure 1. (a) AFM of graphene and its dispersion in TPU matrix; (b) Stable strain sensing behaviors of graphene/TPU nanocomposites with different graphene loadings after stabilization by cyclic loading.

Enhanced thermal-conductive and anti-dripping properties of polyamide composites by 3D graphene structures at low filler content

In this work, 3D graphene structures constructed by graphene foam (GF) were introduced into polyamide-6 (PA6) matrix for the purpose of enhancing the thermal-conductive and anti-dripping properties of PA6 composites. The GF were prepared by one-step hydrothermal method. The PA6 composites were synthesized by in-situ thermal polycondensation method to realize PA6 chains covalently grafted onto the graphene sheets. The 3D interconnected graphene structure favored the formation of the consecutive thermal conductive paths or networks even at relatively low graphene loadings. As a result, the thermal conductivity was improved by 300% to 0.847W·m−1·K−1 of PA6 composites at 2.0wt% graphene loading from 0.210W·m−1·K−1 of pure PA6 matrix. The presence of self-supported 3D structure alone with the covalently-grafted PA6 chains endowed the PA6 composites good anti-dripping properties.

Effect of binder‐free graphene–cetyltrimethylammonium bromide anode on the performance of microbial fuel cells

AbstractBACKGROUNDGraphene has been widely used as an anode modification material to enhance the performance of microbial fuel cells (MFCs). The hydrophobicity of graphene and the insulation of the binders used in the electrode preparation were two adverse factors for performance enhancement of the graphene (G) anodes. In this work, binder‐free graphene–cetyltrimethylammonium bromide (CTAB) anodes (G‐CTAB‐2.5, G‐CTAB‐5 and G‐CTAB‐10) prepared with low loadings of CTAB treated graphene were fabricated through a simple strategy and their performance tested in single‐chamber MFCs.RESULTSThe biofilms on the positively charged and hydrophilic G‐CTAB anodes had higher electrocatalytic activity and more diverse microbial populations than those on the G anode. The G‐CTAB‐5 anode showed the best performance, and the maximum output power density (Pmax) of the MFC was 731.3 mW m−2 which was 3.7 times higher than that of the MFC with the G anode.CONCLUSIONThe results showed that the G‐CTAB anode with very low graphene loading exhibited excellent performance. This work provides new prospects for the development of better graphene anodes to further enhance the performance of MFCs. © 2016 Society of Chemical Industry

Electrical conductivity and mechanical properties of ionic liquid modified shear exfoliation graphene/CO‐PA nanocomposites at extremely low graphene loading

In this study, the ionic liquid (IL) modified shear exfoliation graphene (SEG)/co‐polyamide (IL‐SEG/CO‐PA) nanocomposites were fabricated by an effective and simple solution mixing method. In detail, SEG was fabricated in aqueous phase and then modified by IL, 1‐butyl‐3‐methylimidazolium chloride (BMIMCL) to enhance its dispersion in CO‐PA matrix. The IL‐SEG/CO‐PA nanocomposites were of good properties, such as thermal property, electrical conductivity and mechanical properties, especially a low percolation threshold of not higher than 0.15 wt% (about 0.0523 vol%). The tests and measurements indicated that the Tc, T−50%, and Td‐max of the nanocomposites was 17°C, 18°C, and 22.5°C higher than that of CO‐PA respectively; when SEG content was 0.75 wt%, the electrical conductivity was improved from 2.85 × 10−12 S/m to 1.32 × 10−7 S/m, the tensile strength increased by 43.2%, and yield strength 19.7%. The incorporation of IL resulted in the good exfoliation and dispersion of graphene in CO‐PA matrix, which could be the direct reason for the improvement of the nanocomposites. POLYM. COMPOS., 38:E277–E284, 2017. © 2016 Society of Plastics Engineers

Enhanced protective properties and UV stability of epoxy/graphene nanocomposite coating on stainless steel

Epoxy-Graphene (E/G) nanocomposites with different loading of graphene were prepared via in situ prepolymer- ization and evaluated as protective coating for Stainless Steel 304 (SS304). The prepolymer composites were spin coated on SS304 substrates and thermally cured. Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) were utilized to examine the dispersion of graphene in the epoxy matrix. Epoxy and E/G nanocomposites were characterized using X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) techniques and the thermal behavior of the prepared coatings is analyzed using Thermogravimetric analysis (TGA) and Differential scanning calorimetry (DSC). The corrosion protection properties of the prepared coatings were evaluated using Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV) measurements. In addition to corrosion mitigation properties, the long-term adhesion performance of the coatings was evaluated by measuring the adhesion of the coatings to the SS304 substrate after 60 days of exposure to 3.5 wt% NaCl medium. The effects of graphene loading on the impact resistance, flexibility, and UV stability of the coating are analyzed and discussed. SEM was utilized to evaluate post adhesion and UV stability results. The results indicate that very low graphene loading up to 0.5 wt % significantly enhances the corrosion protection, UV stability, and impact resistance of epoxy coatings.

A novel approach to electroconductive ceramics filled by graphene covered nanofibers

In this study, a novel approach to processing electrically conductive and comparatively cost-effective ceramics by incorporation of the graphene coated oxide ceramic nanofibers into alumina matrix is presented. The conductive fillers are produced by chemical vapour deposition of a few-layered graphene shells on a dielectric substrate of alumina nanofibers of 7–10nm in diameter and an exceptional aspect ratio of 107. Our approach allows utilizing the advantages of reinforcement by fibres and high conductivity of graphene through homogeneous dispersion of the fibres within alumina matrix. The composites are densified using spark plasma sintering at 1380°C with 40MPa pressure for 10min. It is shown that addition of 0.3wt.% of graphene results in increase in electroconductivity of 13 orders of magnitude as compared to the monolithic alumina. Moreover, a low graphene loading does not result in deterioration of hardness of the produced hierarchically structured composites. The strategy proposed in this work can be extended to other insulating materials to produce advanced composites suitable for high-precision electrical discharge machining.

Enhanced molecular level dispersion and interface bonding at low loading of modified graphene oxide to fabricate super nylon 12 composites.

Development of advanced graphene based polymer composites is still confronted with severe challenges due to its poor dispersion caused by restacking, weak interface bonding, and incompatibility with polymer matrices which suppress exertion of the actual potential of graphene sheets in composites. Here, we have demonstrated an efficient chemical modification process with polyethylenimine (PEI) to functionalize graphene oxide which can overcome the above-mentioned drawbacks and also can remarkably increase the overall strength of the nylon 12 composites even at very low graphene loading. Chemical modification was analyzed by various surface characterizations including X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. Addition of only 0.25 and 0.35 wt % modified GO showed 37% and 54% improvement in tensile strength and 65% and 74% in Young's modulus, respectively, compared with that of the neat polymer. The dynamic mechanical analysis showed ∼39% and 63% increment in storage modulus of the nanocomposites. Moreover, the nanocomposites exhibited significantly high thermal stability (∼15 °C increment by only 0.35 wt %) as compared to neat polymer. Furthermore, the composites rendered outstanding resistance against various chemicals.

Epoxy Toughening with Low Graphene Loading

The toughening effects of graphene and graphene‐derived materials on thermosetting epoxies are investigated. Graphene materials with various structures and surface functional groups are incorporated into an epoxy resin by in situ polymerization. Graphene oxide (GO) and GO modified with amine‐terminated poly(butadiene‐acrylonitrile) (ATBN) are chosen to improve the dispersion of graphene nanosheets in epoxy and increase their interfacial adhesion. An impressive toughening effect is observed with less than 0.1 wt% graphene. A maximum in toughness at loadings as small as 0.02 wt% or 0.04 wt% is observed for all four types of graphene studied. An epoxy nanocomposite with ATBN‐modified GO shows a 1.5‐fold improvement in fracture toughness and a corresponding 2.4‐fold improvement in fracture energy at 0.04 wt% of graphene loading. At such low loadings, these graphene‐type materials become economically feasible components of nanocomposites. A microcrack mechanism is proposed based on microscopy of the fracture surfaces. Due to the stress concentration by graphene nanosheets, microcracks may be formed to absorb the fracture energy. However, above a certain graphene concentration, the coalescence of microcracks appears to facilitate crack propagation, lowering the fracture toughness. Crack deflection and pinning likely contribute to the slow increase in fracture toughness at higher loadings.

Reinforcement in melt-processed polymer–graphene composites at extremely low graphene loading level

Abstract We have prepared polymer nanocomposites reinforced with exfoliated graphene layers solely via melt blending. For this study polyethylene terephthalate (PET) was chosen as the polymer matrix due to its myriad of current and potential applications. PET and PET/graphene nanocomposites were melt compounded on an internal mixer and the resulting materials were compression molded into films. Transmission electron microscopy and scanning electron microscopy revealed that the graphene flakes were randomly orientated and well dispersed inside the polymer matrix. The PET/graphene nanocomposites were found to be characterized by superior mechanical properties as opposed to the neat PET. Thus, at a nanofiller load as low as 0.07 wt%, the novel materials presented an increase in the elastic modulus higher than 10% and an enhancement in the tensile strength of more than 40% compared to pristine PET. The improvements in the tensile strength were directly correlated to changes in elongation at break and indirectly correlated to the fracture initiation area. The enhancements observed in the mechanical properties of polymer/graphene nanocomposites achieved at low exfoliated graphene loadings and manufactured exclusively via melt mixing may open the door to industrial manufacturing of economical novel materials with superior stiffness, strength and ductility.

Enhanced mechanical and thermal properties of regenerated cellulose/graphene composite fibers

In this study, a wet spinning method was applied to fabricate regenerated cellulose fibers filled with low graphene loading which was systematically characterized by SEM, TEM, FTIR and XRD techniques. Subsequently, the mechanical and thermal properties of the resulting fibers were investigated. With only 0.2wt% loading of graphene, a ∼50% improvement of tensile strength and 25% enhancement of Young's modulus were obtained and the modified Halpin–Tsai model was built to predict the mechanical properties of composite fibers. Thermal analysis of the composite fibers showed remarkably enhanced thermal stability and dynamic heat transfer performance of graphene-filled cellulose composite fiber, also, the presence of graphene oxide can significantly enhance the thermal conductivity of the composite fiber. This work provided a facile way to improve mechanical and thermal properties of regenerated cellulose fibers. The resultant composite fibers have potential application in thermal insulation and reinforced fibrous materials.

Vulcanization kinetics of graphene/styrene butadiene rubber nanocomposites

This paper presents the influence of graphene on the vulcanization kinetics of styrene butadiene rubber (SBR) with dicumyl peroxide. A curemeter and a differential scanning calorimeter were used to investigate the cure kinetics, from which the kinetic parameters and apparent activation energy were obtained. It turns out that with increasing graphene loading, the induction period of the vulcanization process of SBR is remarkably reduced at low graphene loading and then levels off; on the other hand, the optimum cure time shows a monotonous decrease. As a result, the vulcanization rate is suppressed at first and then accelerated, and the corresponding activation energy increases slightly at first and then decreases. Upon adding graphene, the crosslinking density of the nanocomposites increases, because graphene takes part in the vulcanization process.