Synergistic effects of carbon nanotubes and carbon black on the fracture and fatigue resistance of natural rubber composites

The quasi‐static fracture and dynamic fatigue behaviors of natural rubber composites reinforced with hybrid carbon nanotube bundles (CNTBs) and carbon black (CB) at similar hardness values were investigated on the basis of fracture mechanical methods. Mechanical measurement and J‐integral tests were carried out to characterize the quasi‐static fracture resistance. Dynamic fatigue tests were performed under cyclic constant strain conditions with single‐edged notched test pieces. The results indicate that synergistic effects between CNTBs and CB on the mechanical properties, fracture, and fatigue resistance were obtained. The composite reinforced with 3‐phr CNTBs displayed the strongest fatigue resistance. The synergistic mechanisms and dominating factors of quasi‐static and dynamic failure, such as the dispersion state of nanotubes, hybrid filler network structure, strain‐induced crystallization, tearing energy input, and viscoelastic hysteresis loss, were examined. The weakest fatigue resistance of the composite filled with 5‐phr CNTBs was ascribed to its strikingly high hysteresis, which resulted in marked heat generation under dynamic fatigue conditions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42075.     

Probing the reinforcing mechanism of graphene and graphene oxide in natural rubber

Natural rubber (NR) containing graphene (GE) and graphene oxide (GO) were prepared by latex mixing. The in situ chemically reduction process in the latex was used to realize the conversion of GO to GE. A noticeable enhancement in tensile strength was achieved for both GO and GE filled NR systems, but GE has a better reinforcing effect than GO. The strain‐induced crystallization was evaluated by synchrotron wide‐angle X‐ray diffraction. Increased crystallinity and special strain amplification effects were observed with the addition of GE. The incorporation of GE produces a faster strain‐induced crystallization rate and a higher crystallinity compared to GO. The entanglement‐bound tube model was used to characterize the chain network structure of composites. It was found that the contribution of entanglement to the conformational constraint increases and the network molecular parameters changes with the addition of GE and GO, while GE has a more evident effect than GO. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The effect of partial replacement of carbon black by carbon nanotubes on the properties of natural rubber/butadiene rubber compound

The basic objective of this study is to investigate the mechanical properties of tyre tread compounds by gradual replacement of carbon black by multiwalled carbon nanotubes (MWCNTs) in a natural rubber–butadiene rubber‐based system. A rapid change in the mechanical properties is noticed even at very low concentrations of nanotubes though the total concentration of the filler is kept constant at 25 phr (parts per hundred rubber). The correlation of the bound rubber content with MWCNT loading directly supports the conclusion that MWCNTs increase the occluded rubber fraction. Transmission electron microscopy reveals a good dispersion of the MWCNT up to a certain concentration. In the presence of MWCNT, a prominent negative shift of the glass transition temperature of the compound is found. Thermal degradation behavior, aging, and swelling experiments were also carried out to understand the resulting effect of the incorporation of MWCNT in the rubber matrix. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3153–3160, 2013     

Preparation and properties of octadecylamine modified graphene oxide/styrene‐butadiene rubber composites through an improved melt compounding method

Octadecylamine modified graphene oxide/styrene‐butadiene rubber (GO‐ODA/SBR) composites are prepared by a novel and environmental‐friendly method called “Improved melt compounding”. A GO‐ODA/ethanol paste mixture is prepared firstly, and then blended with SBR by melt compounding. GO‐ODA sheets are uniformly dispersed in SBR as confirmed by scanning electron microscope, transmission electron microscopy, and X‐ray diffraction. The interfacial interaction between GO‐ODA and SBR is weaker than that between GO and SBR, which is proved by equilibrium swelling test and dynamic mechanical analysis. GO‐ODA/SBR show more pronounced “Payne effect” than GO/SBR composites, indicating enhanced filler networks resulted from the modification of GO with ODA. GO‐ODA/SBR composite has higher tensile strength and elongation at break than SBR and GO/SBR composite. The tensile strength and elongation at break for the composite with 5 parts GO‐ODA per hundred parts of rubber increase by 208% and 172% versus neat SBR, respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42907.     

Piezoresistive behavior of graphene nanoplatelets/carbon black/silicone rubber nanocomposite

Silicon rubber (SR) filled with carbon black (CB) and carbon black (CB)/graphene nanoplatelets (GNPs) hybrid fillers are synthesized via a liquid mixing method. The effects of filler type on the electrical properties and piezoresistive properties (near the region of the percolation) of the conductive SR composites are studied. It is suggested that the conductivity of the composite filled with CB/GNPs hybrid fillers in the mass ratio of 2 : 4 is much higher than that in other ratio. Percolation threshold for CB/GNPs/SR is found to be 0.18 volume fractions lower than CB/SR. Moreover, force rang and linearity of GNPs/CB/SR is higher than CB alone filling system. And the repeatability of the GNPs/CB/SR composites is better than CB/SR. Not repetitive index () of them is 0.1 and 0.18, respectively. The results suggest that the GNPs/CB/SR composites provide a new route toward fabrication of flexible piezoresistive sensors with high performance. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39778.     

Simultaneous reduction and surface functionalization of graphene oxide and the application for rubber composites

The simultaneous reduction and functionalization of graphene oxide (GO) was realized through a chemical grafting reaction with a functionalization agent N,N-bis(3-aminopropyl)methylamine (APMEL). The reduced and functionalized reduced GO (rGO-APMEL) sheets can be well dispersed in water without any added surfactant and the formed stable rGO aqueous dispersion can be kept for a long time, which can be used for the preparation of rubber–graphene (GE) composites by latex mixing. The electrostatic interaction between rGO–APMEL (positively charged) and natural rubber latex particles (negatively charged) leads to the formation of NR/rGO–APMEL composites with strong interaction. Compared with blank NR, the tensile strength and modulus for NR/rGO–APMEL increase with the rGO–APMEL loading. Especially, when the filler content is 5 phr, the tensile strength of NR/rGO–APMEL-5 increases by 32.7%, as a control the tensile strength of NR/GO-5 and NR/rGO-5 decrease by 20.1 and 15.6%, respectively. The entanglement-bound rubber tube model was used to analyze the reinforcing effect of GE on NR/rGO–APMEL nanocomposites at a molecular level. This study may provide us a novel approach to prepare well dispersed and exfoliated rGO–polymer nanocomposites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47375.     

Reinforcement of the mechanical properties in nitrile rubber by adding graphene oxide/silicon dioxide hybrid nanoparticles

Graphene oxide (GO) and silicon dioxide (SiO₂) nanoparticles have been hybridized for improving the mechanical and dynamic mechanical properties of nitrile rubber (NBR). SiO₂ nanoparticles were homogeneously dispersed on the surface and between layers of GO, and the new hybrid nanoparticles formed (GO/SiO₂₎ had better thermal stability than GO. To evaluate the mechanical properties, GO/SiO₂/NBR nanocomposites were prepared by solution blending and mechanical solution methods. It was observed that tensile strength increased in a larger grade in GO/SiO₂/NBR nanocomposites than that in GO/NBR and SiO₂/NBR nanocomposites, while the elongation at break only changes smoothly. Moreover, dynamics measurements also indicated that the elasticity increased after adding GO/SiO₂ hybrid nanoparticles in NBR. From morphology's analysis of GO/SiO₂/NBR and GO/NBR nanocomposites, it is was conclude that the hybridization of the GO/SiO₂ was the determining factor for the reinforcement of the mechanical properties and elasticity of the NBR. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46091.     

Magnetically aligning multilayer graphene to enhance thermal conductivity of silicone rubber composites

The increasing demand for packaging materials calls for new technologies to achieve excellent thermal conductivity of polymer composites with low content of thermal conductive filler. This article prepared a kind of magnetically functionalized multilayer graphene (Fe₃O₄@MG) via electrostatic interactions, which efficiently enhanced the thermal conductivity of silicone rubber (SR) composites by the alignment of Fe₃O₄@MG in an external magnetic field. The morphology and structure of the Fe₃O₄@MG together with the thermal conductivity of corresponding Fe₃O₄@MG/SR composites were systematically investigated by SEM, TEM, XRD, elemental mapping, and thermal conductivity tester. The obtained results showed that Fe₃O₄@MG was induced to form chain-like bundles in silicone rubber matrix under the applied magnetic field, which enhanced the MG–MG interaction, and formed effective thermal pathways in the alignment direction. Furthermore, as coating mass ratio of Fe₃O₄@MG increased, the thermal conductivity of randomly oriented Fe₃O₄@MG/silicone rubber composites (R-Fe₃O₄@MG/SR) decreased gradually, whereas the through-plane thermal conductivity of vertically aligned Fe₃O₄@MG/silicone rubber composites (V-Fe₃O₄@MG/SR) increased even filled with same contents of thermal conductive filler. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47951.     

Mechanical and thermal properties of hierarchical composites enhanced by pristine graphene and graphene oxide nanoinclusions

Epoxy resin nanocomposites incorporated with 0.5, 1, 2, and 4 wt % pristine graphene and modified graphene oxide (GO) nanoflakes were produced and used to fabricate carbon fiber‐reinforced and glass fiber‐reinforced composite panels via vacuum‐assisted resin transfer molding process. Mechanical and thermal properties of the composite panels—called hierarchical graphene composites—were determined according to ASTM standards. It was observed that the studied properties were improved consistently by increasing the amount of nanoinclusions. Particularly, in the presence of 4 wt % GO in the resin, tensile modulus, compressive strength, and flexural modulus of carbon fiber (glass fiber) composites were improved 15% (21%), 34% (84%), and 40% (68%), respectively. Likewise, with inclusion of 4 wt % pristine graphene in the resin, tensile modulus, compressive strength, and flexural modulus of carbon fiber (glass fiber) composites were improved 11% (7%), 30% (77%), and 34% (58%), respectively. Also, thermal conductivity of the carbon fiber (glass fiber) composites with 4% GO inclusion was improved 52% (89%). Similarly, thermal conductivity of the carbon fiber (glass fiber) composites with 4% pristine graphene inclusion was improved 45% (80%). The reported results indicate that both pristine graphene and modified GO nanoflakes are excellent options to enhance the mechanical and thermal properties of fiber‐reinforced polymeric composites and to make them viable replacement materials for metallic parts in different industries, such as wind energy, aerospace, marine, and automotive. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40826.     

Dielectric and microwave properties of carbon nanotubes/carbon black filled natural rubber composites

Abstract

Natural rubber (NR) based nanocomposites containing a constant amount (50 phr) of standard furnace carbon black and carbon nanotube (CNT) at a concentration from 1 to 5 phr have been prepared. Their dielectric (dielectric permittivity and dielectric loss) and microwave properties (coefficients of absorption and reflection of the electromagnetic waves and electromagnetic interference shielding effectiveness) have been investigated in the 1–12 GHz frequency range. The results achieved allow recommending CNTs as second filler for NR based composites to afford specific absorbing properties.     

Mechanical properties of graphene nanoplatelet/epoxy composites

Because of their high‐specific stiffness, carbon‐filled epoxy composites can be used in structural components in fixed‐wing aircraft. Graphene nanoplatelets (GNPs) are short stacks of individual layers of graphite that are a newly developed, lower cost material that often increases the composite tensile modulus. In this work, researchers fabricated neat epoxy (EPON 862 with Curing Agent W) and 1–6 wt % GNP in epoxy composites. The cure cycle used for this aerospace epoxy resin was 2 h at 121°C followed by 2 h at 177°C. These materials were tested for tensile properties using typical macroscopic measurements. Nanoindentation was also used to determine modulus and creep compliance. These macroscopic results showed that the tensile modulus increased from 2.72 GPa for the neat epoxy to 3.36 GPa for 6 wt % (3.7 vol %) GNP in epoxy composite. The modulus results from nanoindentation followed this same trend. For loadings from 10 to 45 mN, the creep compliance for the neat epoxy and GNP/epoxy composites was similar. The GNP aspect ratio in the composite samples was confirmed to be similar to that of the as‐received material by using the percolation threshold measured from electrical resistivity measurements. Using this GNP aspect ratio, the two‐dimensional randomly oriented filler Halpin–Tsai model adjusted for platelet filler shape predicts the tensile modulus well for the GNP/epoxy composites. Per the authors' knowledge, mechanical properties and modeling for this GNP/epoxy system have never been reported in the open literature. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effects of crosslinking reaction and extension strain on the electrical properties of silicone rubber/carbon nanofiller composites

Stretchable conductive silicone rubber (SR) composites are important in wearable electronic devices and the crosslinking of SR composites is necessary for their applications. But the effect of the crosslinking reaction on the electrical conductivity of SR composites is rarely reported. In this article, the effect of crosslinking reaction on the electrical conductivity of SR composites filled with conductive carbon black, carbon nanotubes, and graphene are studied. The crosslink density of SR composites increases with increasing curing time, but the electrical conductivity decreases sharply at the early stage of crosslinking, especially for SR/conductive carbon black composite, which is ascribed to the reaggregation of conductive nanofillers in SR during the crosslinking process. The elastic modulus of the three SR composites gradually increases while the elongation at break decreases with increasing curing time, and the SR/carbon black composite shows ultra-high elongation at break (1578%). In addition, SR/graphene composite is more sensitive to the extension strain than SR/carbon black and SR/carbon nanotubes composites, and its gauge factor is 414 at the strain ranges of 3–25%. This research work brings a new method to optimize the crosslinking structure of conductive SR composites.     

Effects of surface modification of carbon nanofibers on the mechanical properties of polyamide 1212 composites

In this study, the effects of carbon nanofiber (CNF) surface modification on mechanical properties of polyamide 1212 (PA1212)/CNFs composites were investigated. CNFs grafted with ethylenediamine (CNF‐g‐EDA), and CNFs grafted with polyethyleneimine (CNF‐g‐PEI) were prepared and characterized. The mechanical properties of the PA1212/CNFs composites were reinforced efficiently with addition of 0.3 wt % modified CNFs after drawing. The reinforcing effect of the drawn composites was investigated in terms of interfacial interaction, crystal orientation, crystallization properties and so on. After the surface modification of CNFs, the interfacial adhesion and dispersion of CNFs in PA1212 matrix were improved, especially for CNF‐g‐PEI. The improved interfacial adhesion and dispersion of CNFs in PA1212 matrix was beneficial to reinforcement of the composites. Compared with pure PA1212, improved degree of crystal orientation in the PA1212/CNF‐g‐PEI (CNF‐g‐EDA) composites was responsible for reinforcement of mechanical properties after drawing. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41424.     

Epoxy/p‐phenylenediamine functionalized graphene oxide composites and evaluation of their fracture toughness and tensile properties

In an attempt to enhance the mechanical properties of epoxy/graphene‐based composites, the interface was engineered through the functionalization of graphene oxide (GO) sheets with p‐phenylenediamine; this resulted in p‐phenylenediamine functionalized graphene oxide (GO–pPDA). The morphology and chemical structure of the GO–pPDA sheets were studied by spectroscopic methods, thermal analysis, X‐ray diffraction, and transmission electron microscopy. The characterization results show the successful covalent functionalization of GO sheets through the formation of amide bonds. In addition, p‐phenylenediamine were polymerized on graphene sheets to form crystalline nanospheres; this resulted in a GO/poly(p‐phenylenediamine) hybrid. The mechanical properties of the epoxy/GO–pPDA composite were assessed. Although the Young's modulus showed improvement, more significant improvements were observed in the strength, fracture strain, and plane‐strain fracture toughness. These improvements were attributed to the unique microstructure and strong interface between GO–pPDA and the epoxy matrix. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43821.     

Thermal and electrical conductivity of melt mixed polycarbonate hybrid composites co‐filled with multi‐walled carbon nanotubes and graphene nanoplatelets

In this work, we present thermoplastic nanocomposites of polycarbonate (PC) matrix with hybrid nanofillers system formed by a melt‐mixing approach. Various concentrations of multi‐walled carbon nanotubes (MWCNT) and graphene nanoplatelets (GnP) were mixed in to PC and the melt was homogenized. The nanocomposites were compression molded and characterized by different techniques. Torque dependence on the nanofiller composition increased with the presence of carbon nanotubes. The synergy of carbon nanotubes and GnP showed exponential increase of thermal conductivity, which was compared to logarithmic increase for nanocomposite with no MWCNT. Decrease of Shore A hardness at elevated loads present for all investigated nanocomposites was correlated with the expected low homogeneity caused by a low shear during melt‐mixing. Mathematical model was used to calculate elastic modulus from Shore A tests results. Vicat softening temperature (VST) showed opposite pattern for hybrid nanocomposites and for PC‐MWCNT increasing in the latter case. Electrical conductivity boost was explained by the collective effect of high nanofiller loads and synergy of MWCNT and GnP. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42536.     

Reduced graphene oxide/carbon nanotubes nanohybrids as preformed reinforcement for polystyrene composites

Three‐dimensional carbon nanohybrids constructed by reduced graphene oxide (rGO) and carbon nanotubes (CNTs) are prepared via simultaneous hydrothermal and chemical reduction reactions. The macroscopic rGO/CNTs monolith is used as the preformed reinforcement for polystyrene (PS) composites to function as the continuous conductive pathway. During hydrothermal reaction, interconnected network consisting of rGO and CNTs, driven by the hydrophobic and π‐π interactions, is formed and then frozen by the following freeze‐drying processing. Fourier transform infrared and X‐ray diffraction results confirm that CNTs play an important role in tuning the amphiphilicity and pore structure of the as‐prepared rGO/CNTs nanohybrids. rGO/CNTs/PS composites prepared via vacuum‐assisted impregnation process exhibit the highest electrical conductivity of 1.21 × 10^?3 S m^?1, which is 11 orders of magnitude higher than that of neat PS. The functional synergies of rGO and CNTs are identified to establish an efficient route for improving the electrical property of polymer based composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45054.     

Mechanical and thermal transmission properties of carbon nanofiber‐dispersed carbon/phenolic multiscale composites

The present article reports the development and characterization of carbon nanofiber (CNF)‐incorporated carbon/phenolic multiscale composites. Vapor‐grown CNFs were dispersed homogeneously in to phenolic resin using an effective dispersion route, and carbon fabrics were subsequently impregnated with the CNF‐dispersed resin to develop carbon fiber/CNF/phenolic resin multiscale composites. Mechanical and thermal transmission properties of multiscale composites were characterized. Elastic modulus and thermal conductivity of neat carbon/phenolic and multiscale composites were predicted and compared with the experimental results. It was observed that incorporation of only 1.5 wt % CNF resulted in 10% improvement in Young's modulus, 12% increase in tensile strength, and 36% increase in thermal conductivity of carbon/phenolic composites. Fracture surface of composite samples revealed the formation of stronger fiber/matrix interface in case of multiscale composites than neat carbon/phenolic composites. Enhancement of above properties through CNF addition has been explained, and the difference between the predicted values and experimental results has been discussed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation of functional reduced graphene oxide and its influence on the properties of polyimide composites

Homogeneous dispersion and strong filler–matrix interfacial interactions were vital factors for graphene for enhancing the properties of polymer composites. To improve the dispersion of graphene in the polymer matrix and enhance the interfacial interactions, graphene oxide (GO), as an important precursor of graphene, was functionalized with amine‐terminated poly(ethylene glycol) (PEG–NH₂) to prepare GO–poly(ethylene glycol) (PEG). Then, GO–PEG was further reduced to prepare modified reduced graphene oxide (rGO)–PEG with N₂H₄·H₂O. The success of the modification was confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis, and Raman spectroscopy. Different loadings of rGO–PEG were introduced into polyimide (PI) to produce composites via in situ polymerization and a thermal reduction process. The modification of PEG–NH₂ on the surface of rGO inhibited its reaggregation and improved the filler–matrix interfacial interactions. The properties of the composites were enhanced by the incorporation of rGO–PEG. With the addition of 1.0 wt % rGO–PEG, the tensile strength of PI increased by 81.5%, and the electrical conductivity increased by eight orders of magnitude. This significant improvement was attributed to the homogeneous dispersion of rGO–PEG and its strong filler–matrix interfacial interactions. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45119.     

Preparation and properties of styrene‐butadiene rubber nanocomposites blended with carbon black‐graphene hybrid filler

Graphene has become an attractive reinforcing filler for rubber materials, but its dispersion in rubber is still a big challenge. In this work, a novel carbon black‐reduced graphene (CB‐RG) hybrid filler was fabricated and blended with styrene‐butadiene rubber (SBR) via simple two‐roll mill mixing. The prepared CB‐RG hybrids had a microstructure with small CB agglomerates adsorbed onto graphene surfaces. CB acted as a barrier preventing the RG sheets from restacking even after drying. Homogeneous dispersion of graphene sheets in SBR matrix was observed by the mechanical mixing method based on the application of the CB‐RG hybrid fillers. Dynamic mechanical analysis showed that Tg of the SBR/CB‐RG blend was higher than that of the SBR/CB blend indicating strong interfacial interactions between RG and SBR due to the high surface area of graphene and the π‐π interaction between SBR and graphene. The tensile properties of SBR/CB‐RG composites improved significantly and the volume resistivity decreased compared with the SBR/CB blends. The thermal stability of SBR composites filled with CB and CB‐RG showed slight difference. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41309.     

Solvothermally reduced graphene oxide/polyimide composites: Structures and thermal and mechanical properties

Solvothermally reduced graphene oxide (SRGO)/polyimide (PI) composites were prepared by in situ polymerization. The structures and components were carefully investigated by X-ray diffraction. Thermal properties were measured by thermogravimetry and dynamic thermomechanical analysis. Mechanical properties were carefully evaluated by tensile testing and scanning electron microscopy. The SRGO/PI composites exhibit extremely high tensile strength and elastic modulus, which is 30% higher than that of pure PI film. Meanwhile, the thermal stability of SRGO/PI composites also displays an obvious enhancement. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47164.