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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. Source

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. Source

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. Source

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. Source

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. Source

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