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Kim D.-H.,Korea University | Lee S.Y.,Hanyang University | Jin J.E.,Korea University | Kim G.T.,Korea University | Lee D.-J.,Korea Institute of Footwear and Leather Technology
Physical Chemistry Chemical Physics | Year: 2014

We report that the decoration of metallic single-walled carbon nanotube (m-SWCNT) networks with cobalt(ii) oxide (CoO) can improve the electrical conductivity of the networks. To measure the electrical conductivity, we prepared m-SWCNT networks between the source and drain electrodes of field-effect transistors (FETs). Then, the amount of CoO nanoparticles (NPs) used for decoration was controlled by treating the FETs with different volumes of a solution containing Co(NO3)2·6H2O. Atomic force microscopy imaging showed that CoO NPs were intensively deposited on the intertubular junction of the m-SWCNT networks. X-ray photoelectron spectroscopy confirmed that the oxidation state of the Co element on m-SWCNT was CoO. Raman spectra revealed that heavy decoration of CoO increased the D-band intensity of the m-SWCNT, indicating that the CoO NPs disordered the sp 2 hybridized carbon atoms of the m-SWCNT via decoration. The electrical conductivity of the m-SWCNT networks was enhanced up to 28 times after decoration, and this was attributed to the CoO NPs connecting the m-SWCNTs at junctions of the networks. © 2014 the Partner Organisations.


Kim D.H.,Yeungnam University | Hwang S.H.,Korea University | Park T.S.,Korea Institute of Footwear and Leather Technology | Kim B.S.,Yeungnam University
Journal of Applied Polymer Science | Year: 2013

We prepared fluororubber (FKM) vulcanizate powder (FVP) via cryogenic grinding of the FKM commonly used in automobiles and assessed the particle size distribution of the resulting powder. We also prepared silicone rubber (SR)/FKM blends at a ratio of 25/75. Varying amounts of FKM were replaced with equal amounts of FVP within the range of 5-40 wt%, and the physical properties of the resulting SR/FKM/FVP blends were investigated and compared. The TGA curves of the SR/FKM/FVP blends obtained during the thermal property investigations indicated that pyrolysis of SR occurred within two temperature ranges, and that the SR/FKM/FVP blends with 5 wt% FVP demonstrated the highest thermal stability. The storage modulus (E') and loss modulus (E'') of the SR/ FKM/FVP blends increased as the FVP content increased. In the SR/FKM/FVP blends with 5 and 10 wt% FVP, very typical elastic-deformation behavior was observed. On the contrary, in 40 wt% FVP, the rubber properties disappeared. The mean particle size of FVP was 41.75 μm, and particle size distribution measurements of the SR/FKM/FVP blends suggest particle coexistence such that FVP was condensed and separated. Copyright © 2012 Wiley Periodicals, Inc.


Mun S.Y.,Korea Institute of Ceramic Engineering And Technology | Mun S.Y.,Hanyang University | Lim H.M.,Korea Institute of Ceramic Engineering And Technology | Ahn H.,Hanyang University | Lee D.J.,Korea Institute of Footwear and Leather Technology
Macromolecular Research | Year: 2014

Thermal conductivities of epoxy composites consisting of carbon fiber (CF) and particulate silicon carbide (SiC) fillers were investigated. Composites composed of both fillers were found to have a higher packing density according to a void volume, than composites composed of either single filler on its own. The thermal conductivities were measured using a laser flash method. The CF-epoxy composite exhibited a higher thermal conductivity than SiC-epoxy composite for a filler loading of 80 wt%. The thermal conductivity of a mixed-filler composite containing 30% CF and 50% SiC by weight was found to be 10.6 W/mK, which is twice the value of that of a CF-epoxy composite, six times greater than that of a SiC-epoxy composite, and approximately 48 times greater than that of unmodified epoxy resin. This increased thermal conductivity is due to the fibrous and particulate morphologies of the fillers, which bring about an increase in the number of contact points throughout reducing void volume and increasing dispersibility of carbon fiber, thus resulting in an improved heat transfer path. © 2014 The Polymer Society of Korea and Springer Sciene+Business Media Dordrecht.


Mun S.Y.,Korea Institute of Ceramic Engineering And Technology | Lim H.M.,Korea Institute of Ceramic Engineering And Technology | Lee D.-J.,Korea Institute of Footwear and Leather Technology
Thermochimica Acta | Year: 2015

Silicon carbide (SiC) coating on pitch-based carbon fiber (SiC/pitch-CF) was prepared by the carbonization of a SiO2 coating layer onto pitch-CF. SiO2 sol and pitch-CF were mixed together and carbonized in a furnace under argon. The effect of the SiC coating on the thermal properties of pitch-CF was investigated. The thermal conductivity of the SiC/pitch-CF-epoxy composite was measured using the laser flash method. Because of the increase in the contact point of pitch-CF owing to the formation of particulate SiC, the thermal conductivity of SiC/pitch-CF was 38% higher than that of uncoated pitch-based CF when compared with epoxy composites comprising 60 wt% filler loading. However, the thermal conductivity of an epoxy composite comprising SiC/microwave-treated pitch-CF (SiC/M.pitch-CF) was lower than that of the pitch-CF-epoxy composite because of the defects resulting from acid treatment, even though the coating layer was fully covered and uniform compared microwave untreated pitch-CF. © 2015 Published by Elsevier B.V.


Kim E.-Y.,Pukyong National University | Lee J.-H.,Korea Institute of Footwear and Leather Technology | Lee D.-J.,Korea Institute of Footwear and Leather Technology | Lee Y.-H.,Pusan National University | And 2 more authors.
Journal of Applied Polymer Science | Year: 2013

As part of an ongoing search for highly hydrophilic waterborne polyurethanes for waterproof breathable fabrics, a waterborne polyurethane [waterborne polyurethane-ureas (WBPU): P70, the number indicates the poly(ethylene glycol) (PEG) content] dispersion was synthesized from PEG (70 wt %) and dimethylol propionic acid (14 mol %) as the hydrophilic/ionic components, 4,4′-diisocyanato dicyclohexylmethane as a diisocyanate, ethylenediamine as a chain extender, and aliphatic tri-isocyanate as a hardener. To determine the best highly hydrophilic WBPU coatings for waterproof breathable fabrics, this study focused on the effect of the hardener content(0-1.2 wt %) in the WBPU P70 sample on the dynamic thermal mechanical properties, contact angle/surface energy, water swelling, water insolubility, and water vapor transmission rate (WVTR). The contact angle, water swelling, glass transition temperature, modulus, and strength increased with increasing hardener content, whereas the surface energy, water insolubility, and WVTR decreased. Sample P70/0.5 (cured sample containing 0.5 wt % of hardener) showed relatively good dimensional stability in water (high water insolubility), strong hydrophilicity (low-water contact angle/high-surface energy/high water absorption), and a high WVTR, highlighting its promising applications in waterproof breathable fabrics. © 2012 Wiley Periodicals, Inc.


Lee S.C.,Korea Institute of Footwear and Leather Technology | Shin E.C.,Korea Institute of Footwear and Leather Technology | Kim W.J.,Korea Institute of Footwear and Leather Technology | Park S.M.,Pusan National University
Journal of the American Leather Chemists Association | Year: 2012

An environmentally friendly nontoxic leather product was produced using two kinds of natural dyes (gallnut and sappan wood) to create a black colorant that can be universally used in leather manufacturing. A chrome free aldehyde and aluminum tanning system was used to prepare the leather for the dye experiments. For the dye preparation experiments gallnut and sappan wood, which are representative polygenetic natural dyes, were extracted by alcohol extraction; then decompressed and refined under concentrating conditions to produce dye in powder form. To produce natural dyed leather with a black color, 5% gallnut and sappan wood were used and the mordant agent, iron mordant (FeSO 4·7H 2O) at 1% of the leather weight, was applied in three different sequences. Applying the mordant simultaneously produced a superior result compared to it application before or after the application of the natural dye. To evaluate the softness and color change of leather, an anionic fatliquor agent was used at 12% of the leather weight. An excellent dark black color and chroma was obtained on the leather surface as a mordant agent and complex compound. The excellent results obtained during the evaluation of rubbing fastness, K/S (coloring matter concentration of surface), and color difference enabled the conclusion that leather with a deep black color could be manufactured with this method.


Kim D.,Pusan National University | Kim D.,Korea Institute of Footwear and Leather Technology | Chung I.,Pusan National University | Kim G.,Korea Institute of Footwear and Leather Technology
Fibers and Polymers | Year: 2013

Recently, carbon fiber composites have been widely used as structural reinforcement materials of buildings, replacing reinforcing bars or concrete. And the increase in use of super fibers such as aramid and high strength PE, which is aimed at improving the reinforcement properties, has resulted in a demand for a resin system with excellent mechanical and thermal properties. In this research, a fiber-reinforced composite has been produced by using the super fibers such as carbon fiber or aramid fiber, reinforcement resin and the silica hybrid compound containing epoxy group. This study was carried out to confirm the effect of the silica hybrid on mechanical properties, heat resistance and adhesion strength of a fiber-reinforced epoxy composite, which was produced by blending silica or introducing silica hybrid through covalent bonds. And the silica hybrid containing epoxy group, which may be introduced to the structure of fiber-reinforced epoxy composite through covalent bonds caused by reaction with a hardener, has been used, so that the heat resistance and adhesion strength could be improved. © 2013 The Korean Fiber Society and Springer Science+Business Media Dordrecht.


Choi K.-M.,Korea Institute of Footwear and Leather Technology | Choi K.-M.,Pusan National University | Choi M.-C.,Korea Institute of Footwear and Leather Technology | Han D.-H.,Korea Institute of Footwear and Leather Technology | And 2 more authors.
European Polymer Journal | Year: 2013

Poly(lactic acid) (PLA) was grafted by low molecular weight acrylated-poly(ethylene glycol) (PEG) via a reactive blending to improve its plasticity. The acrylated-PEG grafted onto PLA was confirmed by the result of nuclear magnetic resonance (NMR) spectra, Fourier transform infrared (FTIR) spectra, wide-angle X-ray diffraction (WAXD) patterns as well as solvent extraction. The properties of the grafted PLAs (PLEAs) were investigated through tensile testing (UTM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and hydrolytic degradable analysis. The glass transition temperature (Tg) of the PLEAs significantly decreased by more than 20 C and the glass transition exhibits at a broad temperature range between 15 and 56 C. The Young's modulus of PLA was lowered by 66% from 1.2 GPa to 0.4 GPa, while the elongation at break of PLA was increased by 380% from 4.7% to 17.9%. © 2013 Elsevier Ltd. All rights reserved.


Kim D.,Korea Institute of Footwear and Leather Technology | Kim D.,Pusan National University | Chung I.,Pusan National University | Kim G.,Korea Institute of Footwear and Leather Technology
Journal of Adhesion Science and Technology | Year: 2012

This paper investigated the design of dismantlable polyurethane adhesives and dismantling method. To study the dismantlement property of dismantlable polyurethane adhesive by controlling thermal property, we synthesized polyurethane adhesive with various hard segment contents and used thermally expansive microcapsules. The dismantlement of bonded adherend was caused by the expansion of the adhesive layer with the expansion of the thermally expansive microcapsule and softening of the adhesive. For the dismantlement of bonded adherend, the adhesive is needed to have low storage modulus at the expansion temperature of thermally expansive microcapsule. High storage modulus of the adhesive was good for the bonding strength but not for dismantlability. In our study, the dismantlability became better as the hard segment content of adhesive decreased and the bonding strength and heat-resistance were excellent when the hard segment content was more than 25% because of high storage modulus and physical property. Consequently, optimum hard segment content was 25%, which showed excellent adhesion strength and dismantlement of bonded adherend was possible with microwave treatment for 4 min. Using zinc oxide with high dielectric constant could shorten microwave treatment time needed for the dismantlement of the bonded adherend to 3min by enhancing the heating efficiency of the adhesive. © 2012 Copyright Taylor and Francis Group, LLC.


Kim I.-J.,Pusan National University | Kim W.-S.,Pusan National University | Lee D.-H.,Pusan National University | Kim W.,Pusan National University | Bae J.-W.,Korea Institute of Footwear and Leather Technology
Journal of Applied Polymer Science | Year: 2010

With the increasing interest in environmental and health issues, legal restrictions, such as European Union (EU) End of Life Vehicle Directives, were strengthened. This led us to incorporate nano zinc oxide (nano-ZnO), with particle sizes of 30-40 nm and specific surface areas of 25.0-50.0 m 2/g, instead of conventional ZnO into natural rubber (NR)/butadiene rubber (BR) compounds to decrease the content of zinc in the formulation. In the unfilled system, only a 20 wt % nano-ZnO content, compared to conventional zinc oxide content, showed the cure characteristics and mechanical properties of the same level. This was because the increase in the specific surface area of the nano-ZnO led to an increase in the degree of crosslinking. The effect of nano-ZnO on the cure characteristics and mechanical properties was more pronounced in the silica-filled system than in the unfilled system. This was mainly because of the dispersing agent used in the silica-filled system, which also improved the dispersion of nano-ZnO. The silica-filled NR/BR compounds containing 0.3-3.0 phr of nano-ZnO showed improved curing characteristics and mechanical properties, such as optimum cure time, 100 and 300% modulus, tensile strength, and tear strength compared to the compound with 5 phr of conventional ZnO. The optimum amounts of nano-ZnO and stearic acid were only 1.0 and 0.1 phr, respectively. © 2010 Wiley Periodicals, Inc.

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