• Composites Research
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• v.27 no.6
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• pp.242-247
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• 2014

The fabrication of flexible electrodes coated on the surface of a dielectric elastomer film, which is a type of electroactive polymer (EAP), was carried out. Controlled amounts of Xylitol powder were added (10, 30, 50 and 70 wt%) to the commercial conductive polymer (PEDOT:PSS) to enhance resilience of the electrode. To check resilience of the fabricated composite electrodes, tensile tests were carried out using silicone films coated with the polymer electrodes. From the test results, it was found that 70 wt% Xylitol containing conductive polymer had excellent elongation and high failure strains. Furthermore, surface of the silicone film was uniformly polished with various abrading papers to enhance the wettability of the conductive polymers on the surface of the silicone film. It was found that the silicone film polished with #120 abrading paper had the best wettability and guaranteed excellent bonding behavior.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.2
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• pp.180-187
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• 2005

This paper is focused on the development of the flexible electrode for disc-type polymer actuators using Segmented Polyurethane(SPU). This paper consists of two parts. The one is about the mechanical property such as elastic modulus. these parameters mainly affect behaviors of polymer actuators and the other is about the electro-chemical property such as the surface resistance of the composite electrode affects the strength of electrostatic force, results in the deformation of polymer actuators. The Young's modulus was measured by UTM. As result, by increasing the modulus of a body of polymer actuators, the maximum displacement of polymer actuators are decreased. The surface resistance of the electrode was measured by 4 point probe system. Compared with the conductive silver grease, the displacement of polymer actuators using carbon black(CB) composite electrodes is comparably small but CB composite electrode should be the practical approach for the improvement of the performance of all-solid actuators, compared with another types of electrode materials.

• Polymer(Korea)
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• v.24 no.2
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• pp.268-275
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• 2000

We investigated the effect of polymer sublayer on volumetric resistivity and tensile strength of carbon fiber (CF)/polyethylene composite films fabricated under high intensity electric fields. The dependence of volumetric resistivity and tensile strength of the films on the polymer sublayer thickness or mass part exhibited complex behavior according to CF content and CF layer density in the films. As the thickness of polymer sublayer increases, two groups of processes at thermo-mechanical forming stage would take effects in the properties of the films. The first group comprises the increase of polymer layer thickness having reduced CF content compared with central or upper part of the film and insufficient wetting of CF resulting in the loosened structure near upper film side. The second group, on the other hand, is the improvement of mobility of molten sublayer leading to better distribution of CF throughout the film thickness and the formation of more compact structure. The different degree of contribution of these two competing processes at varied CF content and CF layer density could explain complex dependence of the film properties on the polymer sublayer. These results are important to optimize the electrical and mechanical properties of highly conductive polymer films, which can be used as electromagnetic interference shielding materials.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.2
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• pp.61-67
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• 2006

Dielectric and conductive frequency spectra in 0.01 Hz-13 MHz range have been measured for the composite consisting of PZT inclusions dispersed in $LiCIO_{4}$-doped polyerhylene oxide(Li_PEO) matrix with various volume fractions. The dielectric and conductive spectra of the composites revealed the relaxations related with electrode polarization and interfacial polarization. The observed spectra were reproduced using the empirical dielectric function and we could obtain various parameters related to the above two kinds of polarizations and dicussed about the parameters.

• Macromolecular Research
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• v.12 no.1
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• pp.53-62
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• 2004

We have prepared polymer composites of low-density polyethylene (LDPE) and ionomers (Surlyn 8940) containing polar segments and metal ions by melt blending with carbon black (CB) as a conductive filler. The resistivity and positive temperature coefficient (PTC) of the ionomer/LDPE/CB composites were investigated with respect to the CB content. The ionomer content has an effect on the resistivity and percolation threshold of the polymer composites; the percolation curve exhibits a plateau at low CB content. The PTC intensity of the crosslinked ionomer/LDPE/CB composite decreased slightly at low ionomer content, and increased significantly above a critical concentration of the ionomer. Irradiation-induced crosslinking could increase the PTC intensity and decrease the NTC effect of the polymer composites. The minimum switching current (Ι$\sub$trip/) of the polymer composites decreased with temperature; the ratio of Ι$\sub$trip/ for the ionomer/LDPE/CB composite decreased to a greater extent than that of the LDPE/CB composite. The average temperature coefficient of resistance (${\alpha}$$\sub$T/) for the polymer composites increased in the low-temperature region.

• Polymer(Korea)
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• v.38 no.6
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• pp.782-786
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• 2014

Various kinds of thermal conductive ceramic/polymer composites (aluminum nitride, aluminum oxide, boron nitride, and silicon carbide/epoxy) were prepared by a casting method and their optical images were observed by FE-SEM. Among these, SiC/epoxy composite shows inhomogeneous dispersion features of SiC and air voids in the epoxy matrix layer, resulting in undesirable thermal conductive properties. To enhance the thermal conductivities of SiC/epoxy composites, the epoxy wetting method which can directly infiltrate the epoxy droplet onto filtrated SiC cake was employed to fabricate the homogeneously dispersed SiC/epoxy composite for ideal thermal conductive behavior, with maximum thermal conductivity of 3.85W/mK at 70 wt% of SiC filler contents.

• Advances in materials Research
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• v.1 no.2
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• pp.161-168
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• 2012

Nanoflake composite multi core-shell $SrFe_{12}O_{19}/Fe_3O_4$/PEG/Polypyrrole was synthesized by in situ polymerization method. In this paper, the fabrication of $SrFe_{12}O_{19}$ nanoflake is as first core by solgel method. Then fabricated a shell layer from magnetic nanoparticles of $Fe_3O_4$, which synthesized by coprecipitation technique, onto the $SrFe_{12}O_{19}$ nanoflake. Polyethylene glycol (PEG) as a polymer layer and as second shell was coated onto the before core-shell. Than core-shell $SrFe_{12}O_{19}/Fe_3O_4$/PEG was used as template for the preparation of $SrFe_{12}O_{19}/Fe_3O_4$/PEG/Polypyrrole composite. Final composite has a conductive property among $4.23{\times}10^{-2}Scm^{-1}$ and magnetic property about $M_s$=2.99 emu/g. Also final composite in soluble at organic solvent such as DMF and DMSO and has a flake structure. Conductivity and magnetic property respectively determine by four-probe instrument and vibrant sample magnetometer (VSM), morphology and article size determined by FE-SEM, TEM and XRD.

• Polymer(Korea)
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• v.29 no.2
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• pp.161-165
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• 2005

$\alpha,\omega-Vinyl$ poly(dimethyl-methylphenyl) siloxane propelymer (VPMPS ) was prepared by the equilibrium polymerization of octamethylcyclotetrasiloxane $(D_4)$, 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane $(D_3^{MePh})$, and 1,1,3,3-tetramethyl-1,3-divinylsiloxane (MVS) as end-blocker. And also, $\alpha,\omega-hydrogen$ poly(dimethyl-methyltrifluoropropyl)siloxane prepolymer (HPDMFS) was prepared from $D_4$, 1,3,5-trimethyl-1,3.5-trifluoropropylcyclotrisiloxane $(D_3^{MeF3P})$, and 1,1,3,3-tetramethyldisiloxane. Poly(organosiloxane) rubber composite containing high thermal conductive filler was prepared by compounding VPMPS, HPDMFS, spherical alumina, and catalyst in high speed dissolver. The crosslinking density of poly (organosiloxane) composite was measured by oscillation rheometer. Poly(organosiloxane) composites of TC-POXR-2 and TC-POXR-4 prepared by controlling average diameters of thermal conductive filler, spherical alumina according to Horsfield's packing model were shown to 1.13 W/mK for TC-POXR-2 and 1.19 W/mK for TC-POXR-4.

• Macromolecular Research
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• v.10 no.5
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• pp.253-258
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• 2002

The multi-wall carbon nanotubes (MWNTs) with graphite crystal structure were synthesized by the catalytic decomposition of a ferrocene-xylene mixture in a quartz tube reactor to use as the conductive filler in the binary polymer matrix composed of poly(vinylidene fluoride) (PVdF) and poly(vinyl pyrrolidone) (PVP) for the EMI (electromagnetic interference) shielding applications. The yield of MWNTS was significantly dependent on the reaction temperature and the mole ratio of ferrocene to xylene, approaching to the maximum at 800 $^{\circ}C$ and 0.065 mole ratio. The electrical conductivity of the MWNTs-filled PVdF/PVP composite proportionally depended on the mass ratio of MWNTs to the binary polymer matrix, enhancing significantly from 0.56 to 26.7 S/cm with the raise of the mass ratio of MWNTs from 0.1 to 0.4. Based on the higher electrical conductivity and better EMI shielding effectiveness than the carbon nanofibers (CNFs)-filled coating materials, the MWNTs-filled binary polymer matrix showed a prospective possibility to apply to the EMI shielding materials. Moreover, the good adhesive strength confirmed that the binary polymer matrix could be used for improving the plastic properties of the EMI shielding materials.

• Composites Research
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• v.35 no.6
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• pp.431-438
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• 2022

Efficient heat dissipation in current electronics is crucial to ensure the best performance and lifespan of the devices along with the users' safety. Materials with high thermal conductivity are often used to dissipate the generated heat from the electronics to the surroundings. For this purpose, polymer composites have been attracted much attention as they possess advantages rooted from both polymer matrix and thermally conductive filler. In order to meet the thermal conductivity required by relevant industries, composites with high filler loadings (i.e., >60 vol%) have been fabricated. At such high filler loadings, however, composites lose benefits originated from the polymer matrix. To achieve high thermal conductivity at a relatively low filler loading, therefore, constructing the heat conduction pathway by controlling filler structure within the composites may represent a judicious strategy. To this end, this review introduces several recent approaches to manufacturing heat dissipating materials with high thermal conductivity by manipulating thermally conductive filler structures in polymer composites.