Low Multiwalled Carbon Nanotubes Content Research Articles

Effect of BaTiO3 Filler Modification with Multiwalled Carbon Nanotubes on Electric Properties of Polymer Nanocomposites.

Two ranges of dielectric permittivity (k) increase in polymer composites upon the modification of BaTiO3 filler with multiwalled carbon nanotubes (MWCNTs) are shown for the first time. The first increase in permittivity is observed at low MWCNT content in the composite (approximately 0.07 vol.%) without a considerable increase in dielectric loss tangent and electrical conductivity. This effect is determined by the intensification of filler-polymer interactions caused by the nanotubes, which introduce Brønsted acidic centers on the modified filler surface and thus promote interactions with the cyanoethyl ester of polyvinyl alcohol (CEPVA) polymer binder. Consequently, the structure of the composites becomes more uniform: the permittivity increase is accompanied by a decrease in the lacunarity (nonuniformity) of the structure and an increase in scale invariance, which characterizes the self-similarity of the composite structure. The permittivity of the composites in the first range follows a modified Lichtenecker equation, including the content of Brønsted acidic centers as a parameter. The second permittivity growth range features a drastic increase in the dielectric loss tangent and conductivity corresponding to the percolation effect with the threshold at 0.3 vol.% of MWCNTs.

The effect of MWCNTs on the properties of peroxide vulcanized ethylene propylene diene monomer (EPDM) composites

Multiwalled carbon nanotubes (MWCNTs) were incorporated in EPDM matrix in an internal mixer. Characterization of the prepared MWCNTs/EPDM composites using RAMAN spectroscopy reveals a minor deterioration of the CNTs’ structure, in terms of intensities ratio of D and G bands (ID/IG ratio), probably due to the intensive mixing conditions of internal mixer. The thermal stability of MWCNTs/EPDM composites was improved, as it was observed by thermogravimetric analysis (TGA) results, whereas the glass transition temperature (Tg) remained almost unaffected. In addition, MWCNTs/EPDM composites showed significant improvement in their modulus of elasticity and a decrease in swelling after immersion in benzene, in comparison with the pristine elastomer. The study of dielectric properties for MWCNT’s/EPDM nanocomposites determined the percolation threshold between 2 and 3 phr MWCNTs content. Enhancement in electromagnetic interference (EMI) shielding effectiveness of MWCNTs/EPDM composites was also recorded by the increase of filler content in the elastomeric matrix, with the reflectance being the main shielding mechanism. A slight increase in thermal diffusivity and conductivity was observed at EPDM composites with low MWCNTs content (1–5 phr) which became more significant at higher loads (8 & 10 phr).

Assessing the electrical property of carbon nanotube reinforced oxide ceramic matrix composites produced by ceramic injection moulding

Owing to its remarkable properties, multiwalled carbon nanotubes (MWCNTs) are attracting the interest for realization of sensors. The potential of MWCNTs for high temperature sensing applications was investigated by integration within reinforced aluminium oxide ceramic composite. MWCNTs up to 2 wt% were mixed with reinforced aluminum oxide ceramic composite using solution mixing method to ensure good homogeneilty of the oxide ceramic composite powders. Specimens were realized using ceramic injection moulding process (CIM) followed by debinding and sintering procedures. The topography of specimens were examined using atomic force microscopy (AFM). Electrical measurements were also carried out. The results show good demouldability at high MWCNTs concentration and homogenous distribution of the MWCNTs within the oxide ceramic matrix. AFM images illustrate the reduction of surface roughness by increasing the MWCNTs content which demonstrates the role of MWCNTs to improve the fracture resistance of the oxide ceramic matrix composite. As well, the electrical resistance of the feedstocks were reduced sharply. After sintering process, the resistance range drops enormously from M Ω to reach 12.1 Ω at low MWCNTs content; which make them suitable to be as electrode with high temperature capability. The electrical resistance temperature dependency shows a negative temperature coefficient behaviour with negligible resistance change.

Investigating the contribution of carbon nanotubes and diesel-biodiesel blends to emission and combustion characteristics of diesel engine

The ultimate purpose of the current research work is to trigger the effect of 50, 100 and 150 ppm multi-walled carbon nanotubes (MWCNTs) in addition to diesel-biodiesel blended fuels with a focus on the emission and combustion characteristics of diesel engine. A single-cylinder diesel engine, with 1800 rpm engine speed and 100% engine load, was used to run the experiments on all fuel blends. The results indicated a significant reduction of the carbon dioxide (CO2) formation as a result of increase in MWCNTs, particularly for B20 and B30 samples. Also, the results emphasized a significant reduction of nitrogen oxides (NOx) formation as fa as B20 and B40 blends were concerned. However, regarding the B10 blends, an increasing trend of NOx emissions were reported when there was an increase in MWCNTs content. Furthermore, increased in-cylinder pressure for the baseline diesel was not found to be influenced by 10% biodiesel addition and 50 ppm MWCNTs. In-cylinder pressure for B10C50 was found to follow the same behaviour as D100 baseline diesel. In addition, the highest in-cylinder pressure of 73.47 bar was attributed to the B10C150 sample, representing a value 4.64% higher than the conventional D100. It was also observed that at low MWCNTs content (50 ppm), the effect on the in-cylinder temperature was the highest. When there was maximum in-cylinder pressure, the 15°CA was determined to be the peak in-cylinder temperature for all samples. All in all, it was confirmed that the combustion characteristics and emission reductions were improved as a result of MWCNTs addition to the biodiesel-diesel blends.

Properties of Waterborne Polyurethane Conductive Coating with Low MWCNTs Content by Electrostatic Spraying.

Because flammable organic solvents are emitted during the construction process, oil-based conductive coatings generally result in potential safety problems. A high content of conductive mediums can also weaken the adhesive and protective abilities of existing conductive coatings. Therefore, an anticorrosive and conductive coating was prepared on Q235 steel substrate by spraying the multi-walled carbon nanotubes (MWCNTs)/waterborne polyurethane (WPU) dispersion with a low MWCNT content in this work. The effect of the MWCNT content on the electrical conductivity, corrosion resistance, and adhesive strength of the WPU conductive coating was investigated. It was concluded that a spatial network structure of MWCNTs-WPU was formed to make the coating structure more compact. The electrical conductivity, corrosion resistance, and adhesive strength of the WPU conductive coating first increased and then decreased as the MWCNT content increased. When the MWCNT content was only 0.2 wt % (which was far lower than that of the existing conductive coatings at 1 wt %), the coating began to conduct electricity; its resistivity was 12,675.0 Ω·m. The best combination property was the 0.3 wt % MWCNTs/WPU conductive coating. Its adhesive strength was 19.99% higher than that of pure WPU coating. Its corrosion rate was about one order of magnitude lower than that of pure WPU coating after being immersed in 3.5 wt % NaCl solution for 17 days.

Fabrication of Carbon Nanotube Reinforced Al2O3/Cr2O3 Nanocomposites by Coprecipitation Process

In this research, the effect of multi-walled carbon nanotubes (MWCNTs) on the alumina/chromia (Al2O3/Cr2O3) nanocomposites has been investigated. Al2O3/Cr2O3-MWCNTs nanocomposites with variable contents of Cr2O3 and MWCNTs were fabricated using coprecipitation process and followed by spark plasma sintering. XRD analysis revealed a good crystallinity of sintered nanocomposites samples and there was only one phase presence of Al2O3-Cr2O3 solid solution. Density, Vickers microhardness, fracture toughness and fracture strength have been measured in the sintered samples. The results show that the relative density, microhardness and fracture strength of nanocomposites are significantly improved at low contents of Cr2O3 and MWCNTs. The increase of MWCNT’s content in the nanocomposites has adversely affected due to increasing the tangle and interaction of MWCNTs with each other, which leads to agglomeration in the nanocomposites. Increasing of Cr2O3 content in nanocomposites increases formation of Al2O3-Cr2O3 solid solution that actually requires the high sintering temperature to achieve good densification. The fracture toughness of Al2O3/Cr2O3-MWCNTs nanocomposites was enhanced by increasing the carbon nanotube content.

Comparison of pristine and polyaniline‐grafted MWCNTs as conductive sensor elements for phase change materials: Thermal conductivity trend analysis

ABSTRACTPhase change materials (PCMs) function based on latent heat stored on or released from a substance over a slim temperature range. Multiwalled carbon nanotubes (MWCNTs) and polyaniline are important elements in sensor devices. In this work, pristine and polyaniline‐grafted MWCNTs (PANI‐g‐MWCNTs) were applied as conductive carbon‐based fillers to make PCMs based on paraffin. The attachment of PANI to the surface of MWCNTs was proved by Fourier transform Infrared analysis. Dispersion of MWCNTs in paraffin was studied by wide‐angle X‐ray scattering. Heating and solidification of PCM nanocomposites were investigated by differential scanning calorimetry, while variation in nanostructure of PCMs during heating/solidification process was evaluated by rheological measurements. It was found that after 30 min of sonication, the samples filled with 1 wt % MWCNTs have melting and solidification temperatures of 29 and 42 °C, respectively. It was also found that PANI attachment to MWCNTs significantly changes thermal conductivity behavior of PCM nanocomposites. The developed MWCNTs‐based sensor elements responded sharply at low MWCNTs content, and experienced an almost steady trend in conductivity at higher contents, while PANI‐g‐MWCNTs sensor followed an inverse trend. This contradictory behavior brought insight for understanding the response of PCMs against thermal fluctuations. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45389.

Influence of Carbon Nanotubes on the Morphology and Properties of Styrene‐Butadiene Based Block Copolymers

SummaryStructure property correlations in a styrene‐butadiene star block copolymer melt mixed with varying amounts of multiwalled carbon nanotubes (MWCNTs) were evaluated. The MWCNTs are well dispersed within the matrix and do not significantly impact the star block copolymer morphology or the glass transition temperature. The electrical percolation threshold was found to be at ∼1 wt% of MWCNT concentration. A distinct increase in Young's modulus could be observed at a nanofiller content of 0.1 wt% while maintaining the elastomeric matrix property profile, an observation in tune with the rule‐of‐mixture prediction. Additionally the existence of double yielding was detected in these nanocomposites with a pronounced first yield point indicating a significant enhancement of stiffness in composites with low MWCNT content. Analysis of elastic moduli using Halpin‐Tsai and two‐phase Takayanagi model revealed a matrix‐controlled elastic response without any interfacial contribution due to MWCNT incorporation.

Thermal behavior and mechanical properties of nanocomposites of polycarbonate reinforced with multiwalled carbon nanotubes

Nanocomposites of polycarbonate (PC) reinforced with different contents (0–10 wt%) of multi‐walled carbon nanotubes (MWCNTs), PC/MWCNT, were prepared in a two‐step dispersion process: extrusion followed by injection molding. The effects of the MWCNT content and injection conditions on thermal, mechanical, and dynamic mechanical properties of the prepared nanocomposites were investigated and compared. Thermogravimetric analysis showed that a small MWCNT content (i.e., 1 wt%) was more propitious for improving thermal stability of the nanocomposites. Analysis of the mechanical properties demonstrated that the tensile properties of the nanocomposites with low MWCNT content could be comparable to that of PC; but as the content was increased to 10 wt%, the tensile strength and bending strength decreased by 35% and 47%, respectively, from the values for PC. The impact strength and microhardness was improved; however, with the increase in MWCNT content. Results of dynamic mechanical analysis showed that the storage modulus of PC was increased by the incorporation of MWCNTs, particularly at high temperatures. Scanning electron microscopy was also carried out to investigate the microstructures of the nanocomposites. It is concluded that the incorporation of MWCNTs by injection molding was more effective in enhancing the thermal, mechanical, and dynamic mechanical properties of PC. POLYM. COMPOS., 38:E303–E313, 2017. © 2015 Society of Plastics Engineers

Relationship between microstructure and mechanical properties in acid-treated carbon nanotube-reinforced alumina composites

Alumina composites reinforced with multiwalled carbon nanotubes (MWCNTs) at up to 3.7 vol% are prepared by a precursor method followed by a spark plasma sintering. We systematically and quantitatively investigate the effects of acid-treatment time of the MWCNTs on not only bending strength and fracture toughness of the composites but also on the mechanical strength and dispersibility of the MWCNTs, the grain size of the alumina matrix, and the interfacial strength between MWCNT and alumina. The main objective of this study is to evaluate how these parameters influence the mechanical properties with the aid of multiple regression analysis. We demonstrate that the matrix grain size, the mechanical strength of the MWCNTs, and the interfacial strength have little impact on the mechanical properties for the composites prepared in this study. On the other hand, the dispersibility of MWCNTs has the significant influence on the mechanical properties. Both the dispersibility of the MWCNTs and the mechanical properties of the composites increase as the acid-treatment time increases up to 2 h at low MWCNT content (0.9 vol%). Conversely, at a higher amount of MWCNTs, the degradation in the mechanical properties is shown to be associated with the deterioration of MWCNTs’ dispersibility. As MWCNT agglomerates are anticipated to act as imperfections, they may override the effects of the strength of MWCNTs, matrix grain size, and interfacial strength. By means of the multiple regression analysis, we quantitatively show that improving MWCNTs’ dispersibility is one of the most important factors in enhancing the mechanical properties of MWCNT/alumina composites.

Mechanical, rheological, and electrical properties of multiwalled carbon nanotube reinforced ASA/Na‐ionomer blend

ABSTRACTVarying amounts of multiwalled carbon nanotubes (MWCNTs) was melt‐extruded with the acrylonitrile‐styrene‐acrylate (ASA)/Na‐ionomer blend, and mechanical, rheological, and electrical properties were studied Optical micrographs show good dispersion level at low MWCNT content and network formation at higher nanotubes percentage. DC conductivity model data shows percolation threshold reached at 1% MWCNT content and after percolation, two‐dimensional network structure was formed. The “peak and valley” type surface topology of matrix may be responsible for low percolation threshold limit. The polymer/nanotubes interactions at low MWCNT content increased the mechanical strengths, which were reduced by the network structure and agglomerates of nanotubes at higher nanotubes content. The MWCNTs interacted differently with the architecturally complex polymer chains and controlled chain dynamics accordingly. The Carreau‐Yasuda model was found fit to viscosity data and the model parameters data suggest the zero shear viscosity is function of MWCNTs content but the infinite shear viscosity is independent of nanoparticles content. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42516.

Competitive Crystallization of a Propylene/Ethylene Random Copolymer Filled with a β-Nucleating Agent and Multi-Walled Carbon Nanotubes. Conventional and Ultrafast DSC Study

A propylene/ethylene polymeric matrix was reinforced by the simultaneous addition of a β-nucleating agent (calcium pimelate) and multi-walled carbon nanotubes (MWCNTs) in various concentrations. The present manuscript explores the competitive crystallization tendency that is caused by the presence of the two fillers. On the one hand, calcium pimelate forces the material to crystallize predominantly in the β-crystalline form, while, on the other, the strong α-nucleating ability of MWCNTs compels the material to develop higher α-crystalline content. An in-depth study has been performed on the nanocomposite samples by means of conventional, temperature-modulated, and differential fast scanning calorimetry (DFSC) under various dynamic and isothermal conditions. The results showed that β-crystals are predominant at low MWCNT content (<2.5 wt %), while, at high MWCNT content, the material crystallizes mainly in the α-form. The recrystallization phenomenon during melting was confirmed with step-scan DSC, and the use of very high cooling rates by UFDSC made it possible to achieve and study the nucleation of the samples. The presence of MWCNTs enabled the nanocomposites to crystallize faster under both isothermal and dynamic conditions. The activation energy of the samples was also calculated according to Friedman's theory.

Enhanced durability of silanized multi-walled carbon nanotube/epoxy nanocomposites under simulated low earth orbit space environment

Silane treated carbon nanotube filled polymer nanocomposites are suggested as a new alternative to reduce the degradation of polymer matrix composites (PMCs) exposed to the low earth orbit (LEO) environment. The silanization of multiwalled carbon nanotubes (MWCNTs) is conducted using 3-aminopropyltriethoxysilane (APTES). Nanocomposites filled with MWCNTs with and without silanization were prepared by the solution mixing method using mechanical/physical approaches to homogeneously disperse the MWCNTs into the polymer matrix. The samples were exposed to an accelerated low earth orbit simulated space environment for 20 h. The synergistic environmental factors used in the ground simulation systems were high vacuum, atomic oxygen (AO), ultraviolet (UV) radiation and thermal cycling. The material properties for nanocomposites reinforced with MWCNTs with and without silanization before and after exposure to the low earth orbit space environment were evaluated by total mass loss (TML), tensile test, thermo-gravimetric analysis (TGA), thermo-mechanical analysis (TMA), and thermo-optical analysis. Surface morphologies of the exposed samples were characterized through scanning electron microscopy (SEM). The results indicated that improvement of the interfacial bonding between the nanotubes and the matrix by the silanization of MWCNTs can considerably reduce the degradation rate and enhance the thermal stability, without sacrificing the thermo-mechanical properties of nanocomposites with very low MWCNT content under LEO space environmental conditions.

Glass fiber hybrid composites molded by RTM using a dispersion of carbon nanotubes/clay in epoxy

Nanocomposites based on epoxy and a mixture of clays and multi-walled carbon nanotubes (MWCNT) were produced by casting, and also molded by RTM using glass fibers as reinforcement, yielding a hybrid multi-scale micro/nanocomposite material. Two types of montmorillonite clays were used, natural (MMT-Na) and organophilic (MMT-30B). Higher viscosity was obtained for the mixture with MMT-30B and it was observed that this clay did not perform as well as the MMT-Na in helping the dispersion of the carbon nanotubes (CNT). The glass transition temperature (Tg) of the nanocomposites increased in up to 6 °C with the addition of MWCNT and up to 10 °C with the addition of MMT-30B, differently from the MMT-Na which did not alter the Tg of the material. By transmission electron microscopy, it was verified that more homogeneous dispersions and more intercalated structures were obtained with the MMT-30B than with the MMT-Na. Finally, the low clay content used and, especially, the very low MWCNT content, did not significantly alter the studied flexural properties.

1508 光造形法により作製したCNT/紫外線硬化樹脂複合材料マイクロエレメントの引張試験(OS15-2 ナノ・マイクロの視点からの変形と破壊の力学)

Mechanical properties of micromaterials are different from those of bulk. Stereolithography is one of promising fabrication techniques for. But mechanical properties of microelements fabricated by stereolithography are not well understood. In the present study, mechanical properties of micro specimens of UV-curable photopolymer and its MWCNT (Multi-Walled Carbon Nanotubes)-reinforced composites fabricated by micro-stereolithography were evaluated by using specially designed tension testing systems. Young's modulus, 0.5% proof stress, tensile strength and elongation determined from tension tests of fabricated micro tension-test specimens. For low MWCNT content, Young's modulus of composites increased with increasing MWCNT content. However, high MWCNT addition reduced Young's modulus of the composites. The tensile strength and the elongation of composites were reduced as the MWCNT content increased.

Morphologies and electrical properties of electrospun poly[(R)‐3‐hydroxybutyrate‐co‐(R)‐3‐hydroxyvalerate]/ multiwalled carbon nanotubes fibers

AbstractElectrospinning process was used to fabricate fine fibers from poly[(R)‐3‐hydroxybutyrate‐co‐(R)‐3‐hydroxyvalerate] embedded with multiwalled carbon nanotubes (MWCNTs). Rotating disc collector was used to provide additional drawing force to stretch and align both the embedded MWCNTs and electrospun fibers themselves. Morphological observation revealed MWCNTs aligned to the fiber axis and protruding from the surface. To understand the electrical properties of the fiber, a single‐composite fiber has been deposited on a substrate, across multiple electrodes. Electrical conductivity of the single‐electrospun fiber with low MWCNT content of 0.2 wt % was calculated to be in a remarkable magnitude of about 2.07 Sm−1. Electrical current flow spanning the fiber length of 1400 μm indicates that the presence of an interconnected network of MWCNTs exists within the fiber. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Catalytic effect of carbon nanotubes on polymerization of cyanate ester resins

Kinetic peculiarities of polycyclotrimerization process of dicyanate ester of bisphenol A (DCBA) in the presence of multi-walled carbon nanotubes (MWCNTs) have been investigated using Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy technique. It has been found that even very small amounts of MWCNTs (0.01-0.1 wt%) catalyze the reaction of polycyclotrimerization of DCBA leading to formation of polycyanurate network (PCN)/MWCNTs nanocom- posite. However, some decrease in final degree of conversion for nanocomposites compared to the neat PCN within the temperature/time schedule used was observed. The kinetic rate constants increased with addition of MWCNTs and energies of activation were found to be significantly decreased even at low contents of MWCNTs.

Pseudoreinforcement effect of multiwalled carbon nanotubes in epoxy matrix composites

AbstractThe carbon nanotube possesses outstanding physical properties. Theoretically, adding carbon nanotubes into a polymer matrix can remarkably improve the mechanical properties of the polymer matrix. In the present work, a series of composites was prepared by incorporating multiwalled carbon nanotubes (MWNTs) into an epoxy resin. The influences of MWNT content and curing temperature on the flexural properties of the epoxy resin were investigated. The results showed that a very low MWNT content should be used to ensure homogeneous dispersion of MWNTs in the epoxy matrix. A higher MWNT content may lead to deteriorated mechanical properties of the composites because of the aggregation of MWNTs. A decline in the flexural properties of the neat epoxy resin with increasing curing temperature was found. However, under the same curing conditions, improvement in flexural properties was observed for the composite with the low MWNT content and a mild curing temperature. The improvement was far beyond the predictions of the traditional short‐fiber composite theory. In fact, this improvement should be attributed to the retarding effect of MWNTs on the curing reaction of epoxy matrix. Therefore, the improvement in the flexural properties was only a pseudoreinforcement effect, not a nano‐reinforcement effect of the MWNTs on the epoxy resin. Perhaps, it is better for MWNTs to be used as functional fillers, such as electrical or thermal conductive fillers, than as reinforcements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3664–3672, 2006