Abstract: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 (… Show more
“…The agglomeration of CNTs away from the MMT‐30B, caused by the intercalation/exfoliation process of this clay in this matrix, could explain the reduction in network formation and consequent decrease in conductivity (Figs. and ) and viscosity . On the other hand, after adding CNT and MMT‐Na + the viscosity of the system increased, supporting the argument of CNT assisted dispersion by MMT‐Na + clay verified by Liu and Grunlan .…”
Section: Resultssupporting
confidence: 84%
“…On the other hand, after dispersing CNT and MMT‐30B in epoxy monomers, the viscosity was lower than the mixture of epoxy and MMT‐30B alone, suggesting the occurrence of agglomeration of nanoparticles . Adding CNT and MMT‐30B also decreased conductivity, which means that the possible network formation is less efficient, indicating that the volume occupied by intercalated/exfoliated MMT‐30B avoids the network formation by CNTs.…”
Section: Resultssupporting
confidence: 76%
“…In this case, the conduction is caused by interfacial polarization in the conductive layer of the aggregates. As mentioned before, viscosimetry tests were performed for the mixtures of epoxy monomers, CNT and clays in our previous work . After sonicating CNT and MMT‐Na + with epoxy monomers, the viscosity of the system increased, supporting the argument of CNT assisted dispersion by MMT‐Na + clay verified by Liu and Grunlan .…”
Section: Resultssupporting
confidence: 74%
“…d and f). These nanocomposites was also characterized by differential scanning calorimetry (DSC) and viscosimetry test, and reported in our previous study . From DSC analyses, it was observed an increase of 10°C on the glass transition temperature ( T g ) in samples with MMT‐30B and no changes on samples with MMT‐Na + .…”
“…The agglomeration of CNTs away from the MMT‐30B, caused by the intercalation/exfoliation process of this clay in this matrix, could explain the reduction in network formation and consequent decrease in conductivity (Figs. and ) and viscosity . On the other hand, after adding CNT and MMT‐Na + the viscosity of the system increased, supporting the argument of CNT assisted dispersion by MMT‐Na + clay verified by Liu and Grunlan .…”
Section: Resultssupporting
confidence: 84%
“…On the other hand, after dispersing CNT and MMT‐30B in epoxy monomers, the viscosity was lower than the mixture of epoxy and MMT‐30B alone, suggesting the occurrence of agglomeration of nanoparticles . Adding CNT and MMT‐30B also decreased conductivity, which means that the possible network formation is less efficient, indicating that the volume occupied by intercalated/exfoliated MMT‐30B avoids the network formation by CNTs.…”
Section: Resultssupporting
confidence: 76%
“…In this case, the conduction is caused by interfacial polarization in the conductive layer of the aggregates. As mentioned before, viscosimetry tests were performed for the mixtures of epoxy monomers, CNT and clays in our previous work . After sonicating CNT and MMT‐Na + with epoxy monomers, the viscosity of the system increased, supporting the argument of CNT assisted dispersion by MMT‐Na + clay verified by Liu and Grunlan .…”
Section: Resultssupporting
confidence: 74%
“…d and f). These nanocomposites was also characterized by differential scanning calorimetry (DSC) and viscosimetry test, and reported in our previous study . From DSC analyses, it was observed an increase of 10°C on the glass transition temperature ( T g ) in samples with MMT‐30B and no changes on samples with MMT‐Na + .…”
“…We ascribe this behavior again to the restrained polymer dynamics in the NC/resin interfaces. This dielectric phenomenon is not impeded by the presence of MWCNT in the samples, probably because the dispersion of the filler particles is not deteriorated by the coexistence of the clay and MWCNT [34], [35]. Concerning the electrical properties, we expect that the sufficiently high NC amount (ࣙ2 wt%) interrupts any created conductive network and weakens the electron tunneling effect, which is assumed in low MWCNT-loaded composites [36].…”
The reinforcing role of clays in modern nanocomposites raises the question upon potential synergies with other fillers, in terms of their microwave properties and performance. To this effect, hybrid, multiphase composites are fabricated to comprise organomodified nanoclay (NC) and multiwalled carbon nanotubes (MWCNTs) or carbon black nanoparticles (CB) at varying concentrations in epoxy resin matrix (ER). The performed electromagnetic (EM) characterization in the 2-18-GHz band reveals that NC generally degrades the effective permittivity ε * eff of the NC/CB/epoxy composites, whereas for 2wt% NC a local ε * eff maximum is observed in the NC/MWCNT/epoxy system. This divergent impact of NC is attributed to different microstructural features affecting the dipolar dielectric polarization. Finally, the composites with high ε * eff contribute to the miniaturization of reflection reducing and shielding panels, since the respective return and transmission loss are found to be dominated by the destructive interference mechanism. For both topologies, the composite loaded with 2wt% NC and 0.5wt% MWCNT is evaluated as the most effective in attenuating the EM waves. Through the analysis of the microwave dielectric properties and the shielding mechanisms, the material design objectives emerge along with the potential of NC/carbon nanotubes composites for suppression of EM interference.
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