• Composites Research
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• v.28 no.6
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• pp.361-365
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• 2015

The influence of MWCNTs on fracture toughness properties of MWCNTs/Nickel-Pitch Fibers/epoxy composites (MWCNTs/Ni-PFs/epoxy) was investigated according to MWCNTs content. Nickel-Pitch-based carbon fibers (Ni-PFs) were prepared by electroless nickel-plating. The surface properties of Ni-PFs were determined by scanning electron microscopy (SEM) and X-ray photoelectron spectrometry (XPS). The fracture toughness of MWCNTs/Ni-PFs/epoxy was assessed by critical stress intensity factor ($K_{IC}$) and critical strain energy release rate ($G_{IC}$). From the results, it was found that the fracture toughness properties of MWCNTs/Ni-PFs/epoxy were enhanced with increasing MWCNTs content, whereas the value decreased above 5 wt.%. MWCNTs content. This was probably considered that the MWCNTs entangled with each other in epoxy due to an excess of MWCNTs.

• Carbon letters
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• v.10 no.4
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• pp.314-319
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• 2009

The surface treatment effects of reinforcement filler were investigated based on the dynamic mechanical properties of mutiwalled carbon nanotubes (MWCNTs)/epoxy composites. The as-received MWCNTs(R-MWCNTs) were chemically modified by direct oxyfluorination method to improve the dispersibility and adhesiveness with epoxy resins in composite system. In order to investigate the induced functional groups on MWCNTs during oxyfluorination, X-ray photoelectron spectroscopy was used. The thermo-mechanical property of MWCNTs/epoxy composite was also measured based on effects of oxyfluorination treatment of MWCNTs. The storage modulus of MWCNTs/epoxy composite was enhanced about 1.27 times through oxyfluorination of MWCNTs fillers at $25^{\circ}C$. The storage modulus of oxyfluorinated MWCNTs (OF73-MWCNTs) reinforced epoxy composite was much higher than that of R-MWCNTs/epoxy composite. It revealed that oxygen content led to the efficient carbon-fluorine covalent bonding during oxyfluorination. These functional groups on surface modified MWCNTs induced by oxyfluorination strikingly made an important role for the reinforced epoxy composite.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.71-74
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• 2005

In this paper, the effects of the MWCNTs on the PTC characteristics of the conventional CB/polymer nanocomposites were investigated. For the uniform dispersion of the MWCNTs in the polymer matrix., nitricacid-treated MWCNTs were dispersed with the dissolved HOPE in the solvent. After evaporating solvent, the dried master batches in the oven were melt blended mixed with CB and HDPE to obtain the PTC materials. The initial resistivity of PTC materials decreased and the PTC intensity increased with the MWCNTs. During three repeated heating and cooling cycles, the PTC materials containing MWCNTs showed a great reproducibility due to the conductive network structures of CB particles and MWCNTs.

• Korean Chemical Engineering Research
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• v.53 no.6
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• pp.703-708
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• 2015

In order to improve the dispersity of nanofiller, polyurethane (PU) nanocomposites were manufactured via poly(propylene gylcol) (PPG) dispersion with MWCNTs prepared by using a ball mill shaker. MWCNTs could be functionalized by treating with the hydrogen peroxide ($H_2O_2$). Tensile strengths and elongations at break of $PU/H_2O_2$ treated MWCNTs nanocomposites were enhanced compared to those of the PU/pristine MWCNTs nanocomposites. The good dispersion of MWCNTs shown in SEM images was obtained by the functionalization of MWCNTs surface. PU/carbon black (CB) composites showed no significant change in the tensile properties. The tensile properties of PU nanocomposites containing pristine MWCNTs or $H_2O_2$ treated MWCNTs were enhanced with increasing dispersion time. As a result, it was certified that the enhanced dispersity of nanofiller brought the improvement of the tensile properties of the MWCNTs based PU nanocomposites.

• Carbon letters
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• v.13 no.2
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• pp.88-93
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• 2012

Polypyrrole (PPy)/multi-walled carbon nanotubes (MWCNTs) composites were prepared by in situ polymerization of pyrrole on the surface of MWCNTs templates to improve the ammonia gas sensing properties. PPy morphologies, formed on the surface of MWCNTs, were investigated by field emission scanning electron microscopy. The thermal stabilities of the PPy/MWCNTs composites were improved as the content of MWCNTs increased due to the higher thermal stability of the MWCNTs. PPy/MWCNTs composites showed synergistic effects in improving the ammonia gas sensing properties, attributed to the combination of efficient electron transfer between PPy/MWCNTs composites and ammonia gas, and the reproducible electrical resistance variation on PPy during the gas sensing process.

• Carbon letters
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• v.8 no.4
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• pp.292-298
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• 2007

In order to investigate functional groups on the surface of Multi-walled Carbon Nanotubes (MWCNTs) induced by oxyfluorination, XPS (X-ray photoelectron spectroscopy) analysis was carried out. All core level spectra of MWCNTs were deconvoluted to several Pseudo-Voigt functions (sum of Gaussian-Lorentzian functions). Both O1s and F1s binding energy of oxyfluorinated MWCNTs shifted high value as increment of fluorine mixing ratio. The carbon-fluorine covalent bonding concentration increased as increment of fluorine mixing ratio. The shape and intensity of OF10-MWCNTs are similar with those of as-received MWCNTs. However, the intensity and binding energies of main peak position of OF20-MWCNTs and OF30-MWCNTs were dramatically increased by oxyfluorination.

• Polymer(Korea)
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• v.37 no.4
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• pp.449-454
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• 2013

In this work, the effect of electroless Ni-plating of multi-walled carbon nanotubes (MWCNTs) on thermal conductivity and fracture toughness properties of MWCNTs/$Al_2O_3$/epoxy composites was investigated. The surface properties of the Ni-plated MWCNTs were determined by scanning electron microscopy (SEM), X-ray photoelectron spectrometry (XPS), and X-ray diffraction (XRD) analyses. Thermal conductivity was tested using a thermal conductivity measuring system. The fracture toughness of the composites was carried out through the critical stress intensity factor ($K_{IC}$) measurement. As a result, the electroless Ni-plated MWCNTs led to a significant change of surface characteristics of the MWCNTs. Thermal conductivity and fracture toughness of the MWCNTs/$Al_2O_3$/epoxy composites were greater than those of non-treated ones. These results were probably due to the improvement of intermolecular interaction between the Ni-MWCNTs and the matrix resins.

• Carbon letters
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• v.12 no.1
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• pp.48-52
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• 2011

The conducting polymer-coated multi-walled carbon nanotubes (MWCNTs) were prepared by template polymerization of aniline and pyrrole on the surface of MWCNTs in order to develop the novel electromagnetic interference (EMI) shielding materials. The conducting polymer phases formed on the surface of MWCNTs were confirmed by field emission-scanning electron microscopy and field emission-transmission electron microscopy. Both permittivity and permeability were significantly improved for the conducting polymer-coated MWCNTs due to the intrinsic electrical properties of MWCNTs and the conducting properties of coated polymers. The electromagnetic waves were effectively absorbed based on the permittivity nature of conducting polymer and MWCNTs preventing the secondary interference from reflecting the electromagnetic waves. The highly improved EMI shielding efficiency was also obtained for the conducting polymer-coated MWCNTs showing the synergistic effects by combining MWCNTs and the conducting polymers.

• Composites Research
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• v.32 no.6
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• pp.375-381
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• 2019

Multiwalled carbon nanotubes (MWCNTs) are covalently functionalized with isocyanates by directly reacting commercial hydroxyl functionalized MWCNTs with excess 4,4'-methylenebis (phenyl isocyanate) (MDI) and hexamethylene diiosocyanate (HDI). HDI-modified MWCNTs results in a higher surface isocyanate density than MDI-modified MWCNTs. Anionic ring-opening polymerization of ε-caprolactam is conducted using a sodium caprolactam initiator in combination with a di-functional hexamethylene-1,6-dicarbamoylcaprolactam activator in the presence of isocyanate functionalized MWCNTs. This polymerization proceeds in a highly efficient manner at relatively low reaction temperature (150℃) and short reaction times (10 min). During the polymerization, the isocyanate functionalized MWCNTs act not only as reinforcing fillers but also as second activators. Nanocomposites with HDI modified MWCNTs exhibit higher reinforcement and faster isothermal crystallization than MDI modified MWCNTs. The results show that PA6 chains grow more effectively from HDI modified MWCNT surface than from MDI modified MWCNT surface, resulting in stronger interaction between PA6 and MWCNTs.

• Bulletin of the Korean Chemical Society
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• v.33 no.5
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• pp.1523-1526
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• 2012

In this work, we prepared activated multi-walled carbon nanotubes/polyacrylonitrile (A-MWCNTs/C) composites by film casting and activation method. Electrochemical properties of the composites were investigated in terms of serving as MWCNTs-based electrode materials for electric double layer capacitors (EDLCs). As a result, the A-MWCNTs/C composites had much higher BET specific surface area, and pore volume, and lower volume ratio of micropores than those of pristine MWCNTs/PAN ones. Furthermore, some functional groups were added on the surface of the A-MWCNTs/C composites. The specific capacitance of the A-MWCNTs/C composites was more than 4.5 times that of the pristine ones at 0.1 V discharging voltage owing to the changes of the structure and surface characteristics of the MWCNTs by activation process.