• Applied Chemistry for Engineering
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• v.8 no.1
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• pp.76-83
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• 1997

Blends of thermotropic liquid crystalline polymer(TLCP) with poly(ethylene terephthalate) (PET) were prepared by the coprecipitation from a common solvent. The blends were processed through a capillary die at $287^{\circ}C$ to produce a monofilament. Morphology and mechanical, thermal properties of blends and composites were examined by differential scanning calorimetry(DSC), tensile test, optical microscopy and scanning electron microscopy. Crystallization kinetics of the blends were investigated by the isothermal DSC method. The Avrami analyses were applied to obtain the information on the crystal growth geometry and factors controlling the rate of crystallization. In the blends, liquid crystalline phase did not reveal any significant macrophase separation and thermal degradation at the processing temperature. From scanning electron micrographs of cryogenic fracture surfaces of extruded fibers, the TLCP domains were found to be more or less finely dispersed with $0.1{\mu}m$ to $0.2{\mu}m$ in size. Interfacial adhesion between the TLCP and matrix polymer was excellent. Tensile strength and modulus of TLCP/PET in-situ fiber composites were enhanced with increasing draw ratio and LCP content.

• Applied Chemistry for Engineering
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• v.29 no.2
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• pp.168-175
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• 2018

In order to investigate the effect of the chemical treatment of bamboo fiber on physical properties of polypropylene (PP)/bamboo fiber (BF) composites, silane coupling agents such as ${\gamma}$-aminopropyltriethoxysilane (APS), ${\gamma}$-glycidoxypropyl-trimethoxysilane (GPS) and ${\gamma}$-mercaptopropyltrimethoxysilane (MRPS) were applied to BF and alkaline treated BF. Morphological properties of the chemically treated BF were confirmed by optical microscope and SEM measurements, and chemical structure changes were confirmed by FT-IR and EDS. TGA results showed that the thermal stability of silane treated BF increased. Based on the analysis of a universal testing machine and an Izod impact test, the flexural and impact properties of PP/silane treated BF composites showed higher values than those of PP/BF composites. The enhancement of interfacial adhesion properties of the PP/BF composite was checked from SEM images of the fracture of specimens after the tensile test.

• Journal of the Korean Applied Science and Technology
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• v.29 no.1
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• pp.141-148
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• 2012

In this study, the composite coating materials with improved thermal insulation property were prepared by incorporating the hydrophobic silica aerogel. The surface modification of silica aerogel was performed to obtain UV curable urethane acrylate hybrid coating sols with good compatibility by using surfactant(Brij 56). The polycarbonate substrates were coated by the prepared composites and cured under UV radiation. The incorporation of aerogel with only 10 vol% of content resulted in remarkable improvement by about 28% in the thermal insulation property of the coated film, as compared with substrate. In addition, increasing aerogel content was found to give minor effect on the variation of optical transparency, adhesion, and surface hardness of the coated film.

• Polymer(Korea)
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• v.30 no.1
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• pp.70-74
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• 2006

Plasticized cellulose diacetate(CDA) was prepared by homogenizing cellulose diacetate(CDA), triacetin(TA) and epoxidized soybean oil (ESO) in a high-speed mixer, then the CDA mixture was mixed with ramie fiber to produce a green composite material. In DMA analysis, the glass transition temperature of plasticized CDA and the composite was observed at $85\;^{\circ}C\;and\;140\;^{\circ}C$, respectively. A composite reinforced with alkali treated ramie fiber exhibited significantly higher mechanical properties, such as $15\;^{\circ}C$ increase in tensile strength as well as $41\;^{\circ}C$ increase in Young's modulus when compared with commercial polypropylene. In the SEM image analysis, much enhanced adhesion between plasticized CDA and alkali treated ramie fiber (AIRa) was observed.

• Korean Journal of Materials Research
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• v.10 no.8
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• pp.551-557
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• 2000

Cu-based leadframe sheets were oxidized ic a hot alkaline solution to black-oxide layer on the surface and molded with epoxy molding compound(EMC), and finally machined to form sandwiched double-cantilever beam(SDCB) and sandwiched Brazil-nut(SBN)specimers to measure the adhesion strength of leadframe-EMC interface. The SDCB and the SBN specimens were designed to measure the adhesion strength in terms fracture toughness under puasi-mode I and mixed mode loadinf, respectively. After the tests, fracture surfaces were analyzed paths were observed in the SDCB-tested speciments, failure paths varied with crack speed and loading conditions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.232-235
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• 2002

Recently developed liquid silicone rubber (LSR) can be cured by platinum catalyzed additional hydrosilylation mechanism and has the advantage of no byproduct compared to traditional millable peroxide curing silicone rubber. We investigated the characteristics of dielectric breakdown of silicone rubber and adhesion properties between semi-conductive LSR and insulating LSR for high voltage application of pre-molded joint (PMJ). In order to understand the dielectric breakdown characteristics, we used the sheet samples and the paired type rogowski insert electrode system. The breakdown strength and adhesion strength of LSR (E-3) were superior to those of several silicone rubbers. Adhesion strength could be improved by curing at high temperature without post-curing process or enhanced by post-curing process. When LSR (E-3) was cured at $(150^{\circ}C{\times}10min$ semi-conductive )${\times}$ ($175^{\circ}C{\times}10min$ insulation), it showed the high breakdown strength with low standard deviation, and good adhesion strength. In this results, we could apply this process to the fabrication of PMJ without post-curing.

• Restorative Dentistry and Endodontics
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• v.25 no.3
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• pp.313-320
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• 2000

The purpose of this study was to evaluate on the interfacial morphology between dentin and restorative materials. In this in vitro study, the cavity wall restorated with 3 different kinds of tooth colored restorative materials [resin-modified Glass Ionomer cement (Fuji II LC), composite resin (Z-100), compomer (Dyract)]. The thirty extracted human molar teeth without caries and/or restorations are used. The experimental teeth were randomly divided into three groups of ten teeth each. In each group, Wedge shaped cavities (width: 3mm, length: 2mm, depth: 1.5mm) were prepared at the cementoenamel junction on buccal and lingual surfaces. The adhesive of composite resin were mixed with rhodamine B. Primer of composite resin, Prime & Bond 2.1 of Dyract and liquid of Fuji II LC were mixed with fluorescein. In group 1, the cavity wall was treatment with dentin conditioner, and then restorated with Fuji II LC. In group 2, the cavity wall was treatment with Prime & Bond 2.1 and then restorated with Dyract. In group 3, the cavity wall was etching with 10% maleic acid, applied with primer and bonding agent and then restorated with Z-100. The interface between dentin and restorative materials was observed by fluoresence imaging with a confocal laser scanning microscope. The results were as follows : 1. In Glass ionomer group, adaptation of resin modified Glass-ionomer restoration against cavity wall is tight, but the crack formed inside of restoration were observed. 2. In Dyract group, the penetration of resin tag is shorter and the width of hybrid layer is narrower than composite resin group. 3. In Z-100 group, primer penetrated deeply through dentinal tubule. Also bonding agent was penetrated along the primer, but the penetration length is shorter than primer part, and in 3-D image, the resin tag is conical shape and lateral branch is observed.

• Elastomers and Composites
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• v.36 no.3
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• pp.195-200
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• 2001

Ultraviolet photografting of acrylic acid onto low density polyethylene was characterized using XPS and contact angle measurement. Effects of surface modification at LDPE and aluminum on LDPE/Al laminate were also investigated. Contact angle decreased significantly at initial state arid tends to level off with increasing UV irradiation time. The improvement of hydrophilicity was due to the presence of acrylic acid on LDPE surface. Graft of acrylic acid onto LDPE was also identified from O1s/C1s ratios in XPS spectrum. Adhesion strength of LDPE-g-AAc/Al laminate showed about 30 times higher than LDPE/A1 system and it could be attributed to the increase of polarity of LDPE surface. Chemical treatment of Al surface using sulfuric acid/sodium dichromate also increased the adhesion strength of LDPE/Al laminate. Adhesion strength of LDPE/Al laminate decreased significantly under acetic acid.

• Elastomers and Composites
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• v.39 no.1
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• pp.3-11
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• 2004

Plasma treatment is frequently used to increase surface functionality and surface activity. It enables to improve various surface properties such as catalytic selectivity, printability, and interfacial adhesion between various materials. Surface or the ethylene-vinyl acetate (EVA) is exposed under an atmospheric pressure plasma torch (APPT), generated by dielectric barrier discharge (DBD), and the treated surfaces are systemically investigated. Argon, air, and oxygen are used as a processing gas. Properties of the treated EVA surfaces are investigated by the zeta-potential measurements and surface free energies. It is shown that the plasma treatment leads to a drastic increase of surface functional groups of EVA, as the increase of its adhesion energy ($G_{IC}$). Therefore, it is concluded that the APPT process is an effective means to improve adhesion of EVA and polyurethane (PU).

• Korean Journal of Materials Research
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• v.18 no.4
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• pp.204-210
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• 2008

$1.5\;{\mu}m$-thick copper films deposited on silicon wafers were successfully bonded at $415^{\circ}C$/25 kN for 40 minutes in a thermo-compression bonding method that did not involve a pre-cleaning or pre-annealing process. The original copper bonding interface disappeared and showed a homogeneous microstructure with few voids at the original bonding interface. Quantitative interfacial adhesion energies were greater than $10.4\;J/m^2$ as measured via a four-point bending test. Post-bonding annealing at a temperature that was less than $300^{\circ}C$ had only a slight effect on the bonding energy, whereas an oxygen environment significantly deteriorated the bonding energy over $400^{\circ}C$. This was most likely due to the fast growth of brittle interfacial oxides. Therefore, the annealing environment and temperature conditions greatly affect the interfacial bonding energy and reliability in Cu-Cu bonded wafer stacks.