• Advanced Composite Materials
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• v.16 no.4
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• pp.385-394
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• 2007

In this study, the effect of molding condition on the tensile properties for plain woven hemp fiber reinforced green composite was examined. The tensile properties of the composite were compared with those of the plain woven jute fiber composite fabricated by the same process. Emulsion type biodegradable resin or polypropylene sheet was used as matrix. The composites were processed by the compression molding where the molding temperature and its heating time were changed from 160 to $190^{\circ}C$ and from 15 to 25 min, respectively. The following results were obtained from the experiment. The tensile property of hemp fiber reinforced polypropylene is improved in comparison with polypropylene bulk. The strength of composite is about 2.6 times that of the resin bulk specimen. Hemp fiber is more effective than jute fiber as reinforcement for green composite from the viewpoint of strength. The molding temperature and time are suitable below $180^{\circ}C$ and 20 min for hemp fiber reinforced green composite. Hemp fiber green composite has a tendency to decrease its tensile strength when fiber content is over 50 wt%.

• Elastomers and Composites
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• v.53 no.1
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• pp.1-5
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• 2018

In the current research, the curing kinetics of a mixture system consisting of a Bisphenol-A type vinyl ester resin and styrene monomer was studied. Methylethylketone peroxide and cobalt octoate were used as the polymerization initiator and accelerator respectively. Thermograms with several different heating rates were obtained using non-isothermal differential scanning calorimetry. Activation energy values analyzed by the Flynn-Wall-Ozawa isoconversional method showed a three-step change with conversion ${\alpha}$: a slight decrease initially for ${\alpha}$ < 0.1, a constant value of 47.9 kJ/mol in the range 0.1 < ${\alpha}$ < 0.7, and a slow increase for 0.7 < ${\alpha}$. When assuming a constant activation energy of 47.9 kJ/mol, an autocatalytic model of the Sestak-Berggren equation was considered as the proper mathematical model of the conversion function, indicating an overall order of 1.2.

• Journal of Technologic Dentistry
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• v.28 no.1
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• pp.43-52
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• 2006

Three t-amines, 4-(dimethylamino)benzoic acid (ABA), 4-(dimethylamino)benzaldehyde (MBA), 4-(dimethylamino)benzophenone (MBP), were investigated as new visible light photoinitiators for a dental resin composite of UDMA in order to improve photopolymerization effect. Three t-amines mixed with three photosensiizers, CQ, PD and DA, respectively. And the photopolymerization effect of photoinitiators were compared with that of 4-(dimethylamino)ethyl methacrylate (AEM), the most widely used photoinitiator. The photopolymerization efficiency of UDMA containing the photoinitiator increased with irradiation time. The increase was in the order: MBP

• Journal of the Korean Ceramic Society
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• v.34 no.10
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• pp.1037-1044
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• 1997

Mechanical properties and water stability of HAC/PVA based MDF cement composite were investigated using polyurethane(PU) resin, silane coupling agent and various PVA. The results were as follows ; The flexural strength of MDF cement composite increased as increasing with PVA content. Low-viscosity PVA developed higher flexural strength than high-viscosity PVA under a drying curing condition. But the strength of water immersed specimen decreased. Water stability of MDF cement improved as increasing with content of PU. Consequently, water stability of polyurethane 7% added MDF cement was about 2 times higher than that of the controlled specimen. Furthermore, the strength and water stability of diamine group based silane couling agent in using MDF cement increased and improved dramatically.

• Elastomers and Composites
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• v.55 no.2
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• pp.103-107
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• 2020

Herein, resin-formed polysilsesquioxanes (PSSQs) were synthesized using monomolecular fluoro silane as a precursor. The synthesized PSSQs exhibited anti-smudge performance and were used as coating liquid. Two structures were acquired by controlling the amount of the silane precursor and the K₂CO₃ catalyst; these materials were used to prepare the anti-smudge coating liquid solution. The synthesized product was analyzed by various methods such as nuclear magnetic resonance spectroscopy, X-ray diffraction analysis, gel permeation chromatography, and water contact angle measurement. The results confirmed that the as-synthesized PSSQs exhibited the ladder structure and had a molecular weight of 5,117 g/mol and water contact angle of 102.31°.

• Fibers and Polymers
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• v.5 no.4
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• pp.259-263
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• 2004

Rubber-modified epoxy resins have been employed as adhesive and matrix materials for glass and corbon-fiber composites. The behavior of fracture around a crack tip for rubber-modified epoxy resin is investigated through the acoustic emission (AE) analysis of compact tension specimens. Damage zone and rubber particles distributed around a crack tip were observed by a polarized optical microscope and an atomic force microscope (AFM). The damage zone in front of pre-crack tip in rubber-modified specimen $(15wt\%\; rubber)$ began to form at about $13\%$ level of the fracture load and grew in size until $57\%$ load level. After that, the crack propagated in a stick-slip manner. Based on time-frequency analysis of AE signals and microscopic observation of damage zone, it was thought that AE signals with frequency bands of 0.15-0.20 MHz and 0.20­0.30 MHz were generated from cavitation in the damage zone and crack propagation, respectively.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.2
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• pp.200-206
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• 1992

The effect of fiber diameter and gauge length on pull-out test for the interfacial properties in fiber reinforced resin composites have been investigated and these results have been arranged as statistical analysis. The fiber and matrix resins used for this study were stainless steel fiber (SUS316) and carbon fiber (high strength type), epoxy and high density polyethylene resin. From this study, it has been found that shear strength are constant regardless of gauge length of pull-out test and coefficient of variation depend on fiber diameter. In addition, it has been found that the interfacial shear strength decreased with the increasing fiber diameter, and in all case, Weibull parameter (m) has approximately 1.2/C.O.V.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.408-410
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• 2012

In this study, High temperature properties of carbon fiber reinforced composites is performed using strand specimens and resin specimens. As for the tensile test at the different temperature, the tensile modulus of resin specimens decreases slightly until the temperature reaches the glass transition temperature. but the tensile modulus of strand specimens maintains tensile modulus at the room temperature. The tensile strength of resin and strand specimens decreases rapidly until the temperature reaches the glass transition temperature.

• Journal of the Korean Applied Science and Technology
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• v.35 no.4
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• pp.1224-1229
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• 2018

In this study, 2-hedroxyethyl methacrylate (2-HEMA) was graft synthesized on water-dispersed polyurethane using polytetramethylene ether glycoll (PTMG), and then the film of resin was prepared and the physical properties of polyurethane resin were measured. The mechanical properties of the synthesized polyurethane resin were measured by using FT-IR, UTM, adhesion performance measuring instrument. As a result of tensile strength measurement, the tensile strength of HPUD4 with high 2-HEMA content was increased to $5.05kgf/mm^2$, the elongation was measured as 285% of the HPUD1 sample not containing 2-HEMA and adhesive strength of HPUD4 sample was measured at 9.1 sec to 635 psi.

• Polymer(Korea)
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• v.36 no.5
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• pp.573-578
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• 2012

In general, most physical properties of wood/polyvinyl chloride (PVC) composites are lower than those of corresponding neat PVC resin because of poor interfacial adhesion between the hydrophilic wood flour and hydrophobic PVC. Therefore, in this study, we treated wood flour with three aminosilanes to improve wood/PVC interfacial adhesion strength, and eco-friendly wood/PVC/nanoclay composites were prepared by melt blending the aminosilane-treated wood flour, a heavy metal free PVC compound, and a type of nanoclay. The effects of treating wood flour with the aminosilanes and adding the nanoclay on the mechanical properties of the composites were investigated. Mechanical properties of the composites were investigated by universal testing machine (UTM), izod impact tester, dynamic mechanical analyzer (DMA), and thermomechanical analyzer (TMA). The tensile properties of the composites with the aminosilane-treated wood flour were considerably higher than those of the composites with neat wood flour. Furthermore, a small amount of the nanoclay improved mechanical properties of the composites. The performance of the wood/PVC composites was considerably improved by using the aminosilane-treated wood flour and the nanoclay.