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Dipak Khastgir - One of the best experts on this subject based on the ideXlab platform.
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microwave dielectric properties and emi shielding effectiveness of poly styrene b styrene butadiene styrene copolymer filled with pani dodecylbenzenesulfonic acid and carbon black
Polymer Engineering and Science, 2012Co-Authors: Anderson R A Schettini, Dipak Khastgir, Bluma G. SoaresAbstract:Conducting composites of polyaniline doped with dodecylbenzenesulfonic acid (PAni.DBSA), carbon black (CB) and poly(styrene-b-styrene-butadiene-b-styrene) (STF) as supporting matrix were prepared by in situ polymerization. The influence of components and composition (% w/w) on the electromagnetic properties (dielectric constant e′ and the dielectric loss e″) and electromagnetic interference shielding effectiveness (EMI-SE) of the materials were evaluated with a waveguide, using a microwave network analyzer from 8.2 to 12.4 GHz (X-band). It was found that CB presence generates adverse effects on PAni.DBSA yield during synthesis, as it can be seen by X-ray diffraction and TGA analyses. The type of PAni.DBSA formed modifies the composites properties. Dielectric constant, loss factor, and EMI shielding increase with Conductive Filler loading. Both the Fillers, individually and in combination, increase the properties; however, the effect is not additive in nature. POLYM. ENG. SCI., 52:2041–2048, 2012. © 2012 Society of Plastics Engineers
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effect of axial stretching on electrical resistivity of short carbon fibre and carbon black filled Conductive rubber composites
Polymer International, 2002Co-Authors: Narayan Ch Das, T K Chaki, Dipak KhastgirAbstract:The variation of electrical resistivity of carbon black and short carbon fibre (SCF) filled rubber composites was studied against the degree of strain at constant strain rate. It was found that both the degree of strain and strain rate affect the electrical resistivity of the composites. The change in resistivity against the strain and strain rate depends both on the concentration and the type of Conductive Filler. The incorporation of short carbon fibres (SCF) imparts higher conductivity to the composite than carbon black at the same level of loading. Composites filled with carbon black exhibit better mechanical properties than SCF filled composites. Electrical setting, ie a permanent change in electrical resistivity, was observed during extension–retraction cycles. A good correlation was found between the mechanical response and the electrical response towards strain sensitivity. The results of different experiments are discussed in the light of breakdown and formation of Conductive networks in the filled rubber composites. © 2002 Society of Chemical Industry
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Conductive rubber composites from different blends of ethylene propylene diene rubber and nitrile rubber
Journal of Materials Science, 1997Co-Authors: T K Chaki, Dipak KhastgirAbstract:Conductive rubber composites were derived from different blends of ethylene-propylene-diene monomer (EPDM) rubber and acrylonitrile butadiene rubber (NBR) containing acetylene black. The electrical and mechanical properties of these composites were measured. The percolation limit for achieving high conductivity of Conductive Filler depends on the viscosity of the blend. The higher the viscosity, the higher is the percolation limit. The conductivity rises with increasing temperature, and the activation energy of conduction increases with the decrease in the loading of Conductive Filler and percentage of NBR in the blend. Electrical hysteresis and an electrical resistivity difference during the heating-cooling cycle are observed for these systems, which is mainly due to some kind of irreversible change occurring in the Conductive networks during heating. The mechanisms of conduction of these systems were discussed in the light of different theories. It was found that the degree of reinforcement by acetylene black in blends compares with those in the pure components NBR and EPDM. This is due to incompatibility of two elastomers in the blend.
Soojin Park - One of the best experts on this subject based on the ideXlab platform.
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imidazolium optimized Conductive interfaces in multilayer graphene nanoplatelet epoxy composites for thermal management applications and electroactive devices
Polymer, 2019Co-Authors: Yinhang Zhang, Soojin ParkAbstract:Abstract Imidazolium-based ionic liquid-modified multilayer graphene nanoplatelets (IL@GNPs) derived from atmospheric-pressure plasma-induced expanded graphite (p-EG) were prepared and employed to obtain Conductive Filler–matrix networks in epoxy (EP)-based electroactive devices. The thermal conductivity, electrical properties, and thermo-physical properties of the fabricated composites were evaluated as a function of the IL@GNPs content. Large volume expansion of the plasma-induced EG and few-layer IL@GNPs were observed. The thermal and electrical conductivities and thermo-physical properties of the developed EP/IL@GNPs composites were significantly enhanced compared to the EP/expandable graphite (EaG) and EP/GNPs composites at the same Filler concentration, attributed to the well-exfoliated and IL-functionalized IL@GNPs, which can efficiently construct a Conductive Filler network in the matrix, and optimize the thermal interface between the Filler and the polymer matrix. The designed polymeric materials could be potentially applied in thermal interface materials and other high-performance electroactive devices.
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preparation and characterization of carbon black pitch based carbon fiber paper composites for gas diffusion layers
Composites Part B-engineering, 2019Co-Authors: Youngjung Heo, Mira Park, Wooseok Kang, Kyong Yop Rhee, Soojin ParkAbstract:Abstract We prepared carbon Ketjenblack (KB)/carbon fiber papers (CFPs) from pitch-based carbon fibers (CFs) by web-laid processing, and the electrical conductivity and mechanical properties of the CFPs were investigated according to the structure and morphology of the CFs by the addition of KB as a Conductive Filler at different carbonization temperatures. The wet-laid processing fabrication method for CFPs consisted of four steps: dispersion of CFs, preparation of a CF web, impregnation of phenol resin, and heat treatment. The results showed that the electrical resistance and tensile strength of the CFPs were low at high-heat-treatment temperatures. Notably, CFPs with a thickness of 190 μm, porosities of 86.7%, and specific resistance of 7.795 × 10−2 Ω cm were obtained by after adding 6 wt.% of KB at a carbonization temperature of 800 °C.
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electromagnetic interference shielding behaviors of carbon fibers reinforced polypropylene matrix composites ii effects of Filler length control
Journal of Industrial and Engineering Chemistry, 2014Co-Authors: Myungsun Hong, Soojin Park, Woongki Choi, Shinjae Kang, Young Sil Lee, Byung Joo KimAbstract:Abstract In this work, the electromagnetic interference (EMI) shielding effectiveness (SE) of carbon fiber (CF)-reinforced polypropylene matrix composites in the presence of carbon nanotubes (CNT) as Conductive Filler were investigated by variation of the mixing speed and time to observe the effects of average lengths of carbon fibers on the EMI-SE of the composites. The EMI-SE of the composites increased with increasing mixing speed due to the function of fiber length. It was probably due to the enhanced dispersion of CFs in the composites, resulting in the improvement of the electrical networks and the EMI-SE in the CFs-PP composites.
Y H Koh - One of the best experts on this subject based on the ideXlab platform.
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electromagnetic interference shielding performance of epoxy composites filled with multiwalled carbon nanotubes manganese zinc ferrite hybrid Fillers
Journal of Magnetism and Magnetic Materials, 2016Co-Authors: C H Phan, M Mariatti, Y H KohAbstract:Abstract An effective electromagnetic-interference (EMI) shielding epoxy composite has been fabricated with a combination of multiwalled carbon nanotubes (MWCNTs) and manganese zinc ferrite (MnZn ferrite) Fillers. MWCNTs were functionalized to improve dispersibility while manganese zinc ferrite nanoparticles were synthesized via the citrate gel method. The EMI-shielding performance of the fabricated composites was examined. It was found that the composite with a Filler ratio of MWNCTs to MnZn ferrite=3:1 obtained the highest EMI shielding effectiveness (SE), with the shielding mechanism dominated by absorption. In addition, the EMI shielding performance of composites was improved by increases in the Filler loading and thickness of composites. Composites with a Filler loading of 4.0 vol% and thickness of 2.0 mm achieved an SE of 44 dB at 10 GHz with the assistance of Conductive silver backing. This EMI SE is better than that of composites filled with single Conductive Filler and comparable with that of commercial EMI absorber.
Woo Nyon Kim - One of the best experts on this subject based on the ideXlab platform.
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effects of hybrid Fillers on the electromagnetic interference shielding effectiveness of polyamide 6 Conductive Filler composites
Journal of Materials Science, 2014Co-Authors: Tae Wook Yoo, Yun Kyun Lee, Seung Joon Lim, Ho Gyu Yoon, Woo Nyon KimAbstract:The effects of hybrid Conductive Fillers on the electrical conductivity and electromagnetic interference shielding effectiveness (EMI SE) of polyamide 6 (PA6)/Conductive Filler composites were investigated. Nickel-coated carbon fiber (NCCF) was used as the main Filler and multi-walled carbon nanotube (MWCNT), nickel-coated graphite, carbon black, and titanium dioxide (TiO2) were used as the second Fillers in this study. From the results of morphological studies of the PA6/NCCF/second Filler composites, NCCF easily formed an electrical pathway since it has a high aspect ratio and random orientation, and the second Fillers seemed to disperse evenly in the PA6 matrix. The electrical conductivity and EMI SE of the PA6/NCCF composites were increased with the increase of NCCF content. Among the second Fillers used in this study, TiO2 appeared to be the most effective second Filler with regard to increasing the EMI SE and electrical conductivity of the PA6/NCCF composite. This was probably because TiO2 has a high dielectric constant with dominant dipolar polarization, consequently leading to greater shielding effectiveness due to the absorption of electromagnetic waves. From the above results of EMI SE and electrical conductivity, it was suggested that the TiO2 produced a synergistic effect when it was hybridized with the NCCF of the PA6/NCCF/TiO2 composites.
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effects of hybrid Fillers on the electrical conductivity and emi shielding efficiency of polypropylene Conductive Filler composites
Macromolecular Research, 2013Co-Authors: Dong Hyup Park, Yun Kyun Lee, Sang Sun Park, Choon Soo Lee, Sung Hyun Kim, Woo Nyon KimAbstract:In this study, the effects of hybrid Fillers on the electrical conductivity and electromagnetic interference shielding efficiency (EMI SE) of the polypropylene (PP)/Ni-coated carbon fiber (NCCF) composites with the second Fillers, such as multi-walled carbon nanotube (MWCNT), carbon black and TiO2, were investigated. The morphological behavior showed that the NCCF and the second Fillers, such as MWCNT, carbon black and TiO2, seemed to disperse evenly in the PP phase. Among the PP/NCCF composites with MWCNT, carbon black and TiO2, the PP/NCCF/TiO2 composites showed the higher electrical conductivity and EMI SE compared with those of the PP/NCCF/MWCNT and PP/NCCF/carbon black composites. This was the case because TiO2 has high dielectric constant with dominant dipolar polarization. The estimated EMI SE values of the PP/NCCF composites with MWCNT, carbon black and TiO2 are in good agreement with the experimentally obtained values of the composites. Based on the electrical properties of the composites, it was suggested that TiO2 was the most effective second Filler when it was hybridized with the NCCF of the PP/NCCF/TiO2 composite. Based on the analysis of the flexural modulus, the PP/NCCF/MWCNT composite had a higher flexural modulus than the PP/NCCF/TiO2 and PP/NCCF/carbon black composites because of the higher aspect ratio of the MWCNT. Open image in new window
T K Chaki - One of the best experts on this subject based on the ideXlab platform.
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effect of axial stretching on electrical resistivity of short carbon fibre and carbon black filled Conductive rubber composites
Polymer International, 2002Co-Authors: Narayan Ch Das, T K Chaki, Dipak KhastgirAbstract:The variation of electrical resistivity of carbon black and short carbon fibre (SCF) filled rubber composites was studied against the degree of strain at constant strain rate. It was found that both the degree of strain and strain rate affect the electrical resistivity of the composites. The change in resistivity against the strain and strain rate depends both on the concentration and the type of Conductive Filler. The incorporation of short carbon fibres (SCF) imparts higher conductivity to the composite than carbon black at the same level of loading. Composites filled with carbon black exhibit better mechanical properties than SCF filled composites. Electrical setting, ie a permanent change in electrical resistivity, was observed during extension–retraction cycles. A good correlation was found between the mechanical response and the electrical response towards strain sensitivity. The results of different experiments are discussed in the light of breakdown and formation of Conductive networks in the filled rubber composites. © 2002 Society of Chemical Industry
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Conductive rubber composites from different blends of ethylene propylene diene rubber and nitrile rubber
Journal of Materials Science, 1997Co-Authors: T K Chaki, Dipak KhastgirAbstract:Conductive rubber composites were derived from different blends of ethylene-propylene-diene monomer (EPDM) rubber and acrylonitrile butadiene rubber (NBR) containing acetylene black. The electrical and mechanical properties of these composites were measured. The percolation limit for achieving high conductivity of Conductive Filler depends on the viscosity of the blend. The higher the viscosity, the higher is the percolation limit. The conductivity rises with increasing temperature, and the activation energy of conduction increases with the decrease in the loading of Conductive Filler and percentage of NBR in the blend. Electrical hysteresis and an electrical resistivity difference during the heating-cooling cycle are observed for these systems, which is mainly due to some kind of irreversible change occurring in the Conductive networks during heating. The mechanisms of conduction of these systems were discussed in the light of different theories. It was found that the degree of reinforcement by acetylene black in blends compares with those in the pure components NBR and EPDM. This is due to incompatibility of two elastomers in the blend.