• Title/Summary/Keyword: Crystalline epoxy

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Effect of Silica Content on the Dielectric Properties of Epoxy/Crystalline Silica Composites

  • Park, Jae-Jun
    • Transactions on Electrical and Electronic Materials
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    • v.13 no.6
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    • pp.322-325
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    • 2012
  • Crystalline silica was synthesized by annealing amorphous silica at $1,300^{\circ}C$ or $1,400^{\circ}C$ for various times, and the crystallinity was estimated by X-ray diffraction (XRD) analysis. In order to prepare a low dielectric material, epoxy/crystalline silica composites were prepared, and the effect of silica content on the dielectric properties was studied under various functions of frequency and ambient temperature. The dielectric constant decreased with increasing crystalline silica content in the epoxy composites, and it also decreased with increasing frequency. At 120 Hz, the value of 5 wt% silica decreased by 0.25 compared to that of 40 wt% silica, and at 23 kHz, the value of 5 wt% silica decreased by 0.23 compared to that of 40 wt% silica. The value increased with increasing ambient temperature.

Thermal Decomposition Energy of Liquid Crystalline Epoxy (열경화성 액정 에폭시 수지의 열분해 활성화에너지)

  • Seung Hyun Cho
    • Composites Research
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    • v.37 no.1
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    • pp.1-6
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    • 2024
  • A liquid crystalline thermosetting epoxy was synthesizes with DGE-DHMS and 1-Methyl Imidazole. To investigate thermal stability, activation energies for thermal decomposition were calculated via Flynn-Wall-Ozawa method and Kissinger method with the data obtained from TGA analysis. The result showed that there were no differences in thermal decomposition behavior between liquid crystalline phases and isotropic phase and also the same thermal decomposition mechanism was applied to the entire process.

Thermal Decomposition Activation Energy of Liquid Crystalline Epoxy using Cationic Initiator (양이온 개시제를 이용한 열경화성 액정 에폭시의 열분해 활성화에너지)

  • Jung, Ye Ji;Hyun, Ha Nuel;Cho, Seung Hyun
    • Composites Research
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    • v.34 no.3
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    • pp.180-185
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    • 2021
  • Due to the formation of random three dimensional network structure, which cause a lot of scattering of phonons, the thermal conductivity is low when the liquid crystalline epoxy is cured with amine-based curing agent. This problem is solved by using a cationic initiator that can make mesogen groups to be stacked structure. In this experiment, the thermal stability is compared by investigating the activation energy of isothermal decomposition through TGA of an epoxy using an amine-based curing agent and a cationic initiator. As a result, the energy of the activation of the epoxy using a cationic initiator is high. Compared with the previous experiments, the thermal stability is similar to the thermal conductivity.

Research of Thermal Properties for Liquid Crystalline Epoxy Composites with Tin Oxide Filler (산화주석을 함유한 열경화성 액정 에폭시의 열적 특성에 관한 연구)

  • Hyun, Ha Nuel;Cho, Seung Hyun
    • Composites Research
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    • v.33 no.1
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    • pp.25-29
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    • 2020
  • A liquid crystalline thermosetting-epoxy-based composite was fabricated using diglycidyl ether of 4,4'-biphenol, tin(IV) oxide as a filler, and sulfanilamide as a curing agent. To investigate the thermal behavior, Thermogravimetric Analysis and Laser Flash Apparatus were performed using 3.0-7.0 wt% Tin(IV) oxide. The result showed that the activation energy and thermal conductivity were proportional to the amount of added filler.

Development of Epoxy Composites with SWCNT for Highly Thermal Conductivity (고방열 재료 개발을 위한 에폭시/단일벽 탄소나노튜브 복합체 개발)

  • Kim, Hyeonil;Ko, Heung Cho;You, Nam-Ho
    • Composites Research
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    • v.33 no.1
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    • pp.7-12
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    • 2020
  • Over the past decade, liquid crystalline epoxy (LCER) has attracted much attention as a promising matrix for the development of efficient heat dissipation materials. This study presents a comprehensive study including synthesis, preparation and chacterization of polymer/inorganic composites using typical 4,4-diglycidyloxybiphenyl (DP) epoxy among LECR. To confirm the thermal conductivity of composite materials, we have prepared composite samples composed of epoxy resin and single-wall carbon nanotube (SWCNT) as a filler. In particular, DP composites exhibit higher thermal conductivity than commercial epoxy composites that use the same type of filler due to the highly ordered microstructure of the LCER. In addition, the thermal conductivity of the DP composite can be controlled by controlling the amount of filler. In particular, the DP composite containing a SWCNT content of 50 wt% has the highest thermal conductivity of 2.008 W/mK.

Development of Highly Thermal Conductive Liquid Crystalline Epoxy Resins Bearing Phenylcyclohexyl Mesogenic Moieties (Phenylcyclohexyl mesogenic moieties를 함유한 고 열전도성 액정성 에폭시 수지의 개발)

  • Jeong, Iseul;Kim, Youngsu;Goh, Munju
    • Composites Research
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    • v.30 no.6
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    • pp.350-355
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    • 2017
  • The new liquid crystalline (LC) epoxy was designed by substituting the phenylcyclohexyl (PCH) mesogen moiety with an alkyl chain at the 2,5 position of the diglycidyl terephthalate. The mesomorphic properties were evaluated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). All LC epoxy derivatives exhibited an enantiotropic smectic phase upon heating and cooling process. The LC phase temperature range was widened by mixing the eutectic mixture of LC epoxies. Interestingly, the cured LC epoxy exhibited the highest thermal conductivity of $0.4W{\cdot}m^{-1}{\cdot}K^{-1}$. The novel LC epoxy with high thermal conductivity might be used as a composite material for electronic and display devices.

Synthesis and Curing Behavior of Crystalline Biphenyl Epoxy Resin (결정성 바이페닐 에폭시 합성 및 경화 거동 연구)

  • Choi, Bong-Goo;Choi, Ho-Kyoung;Choi, Jae-Hyun;Choi, Joong-So
    • Korean Chemical Engineering Research
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    • v.58 no.1
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    • pp.44-51
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    • 2020
  • The basic catalyst 1-benzyl-3-methyl-imidazolium hexafluoroantimonate (BMH) was synthesized and analyzed by FT-IR and 1H-NMR. A crystalized biphenyl-based epoxy was synthesized by using tetramethyl biphenol (TMBP) and epichlorohdrine. In order to consider the curing tendency of the synthesized BMH, the mass ratio was changed to 0.5, 1.0, 2.0 wt.% under heated conditions and the curing tendency was analyzed by differential scanning calorimeter (DSC). As a result, the BMH catalyst showed a fast curing result in the stepwise heating pr℃ess of the biphenol-A epoxy and the cationic polymer. From these results, the BMH catalyst showed excellent thermal stability as a potential heat curing catalyst. In addition, we considered the application possibility of epoxy molding compound (EMC) which required a skeleton structure and a high heat resistance because the synthesized biphenyl epoxy had a characteristic of rapidly lowering viscosity at a constant temperature and a rigid skeleton structure of biphenol. As a result, it was confirmed that the TMBP-based epoxy developed in this study was composed of a crystalline structure, and a curing reaction was observed with a Novolac resin at a high temperature. In the presence of a catalyst, a curing reaction was observed around 150 ℃ and thus TMBP-based epoxy was successfully applied as a raw material of EMC.

Microstructural Morphology of Molded Thin Composites of Thermotropic Liquid Crystalline Polymer and Polyamide 6 (서모트로픽 액정폴리머와 폴리아미드6으로 성형된 얇은 복합재료의 미세구조형태)

  • Choe, Nak-Sam;Choe, Gi-Yeong;Ha, Seong-Gyu
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.7 s.178
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    • pp.1703-1711
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    • 2000
  • Microstructural morphology of molded composites of thermotropic liquid crystalline polymer(LCP) and polyamide 6 (PA6) has been studied as a function of epoxy fraction. Injection-moulding of a thin composite plaque at a temperature below the melting point of the LCP fibrils by suing the extruded LCP/PA6 pellets produced multi-layered structures: 1) the surface skin layer with thickness of 65-120 ym exhibiting a transverse orientation, 2) the sub-skin layer with an orientation perpendicular to the surface skin, i.e. in the flow direction, 3) the core layer with arc-curved flow patterns. Similar microstructural orientations were observed in the respective layers for the composite plaques with different fractions of epoxy.

Development of Highly Thermal Conductive Liquid Crystalline Epoxy Resins for High Thermal Dissipation Composites (고방열 복합소재 개발을 위한 고열전도성 액정성 에폭시 수지의 개발)

  • Kim, Youngsu;Jung, Jin;Yeo, Hyeonuk;You, Nam-Ho;Jang, Se Gyu;Ahn, Seakhoon;Lee, Seung Hee;Goh, Munju
    • Composites Research
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    • v.30 no.1
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    • pp.1-6
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    • 2017
  • Epoxy resin (EP) is one of the most famous thermoset materials. In general, because EP has three-dimensional random network, it possesses thermal properties like a typical heat insulator. Recently, there has been increasing interest in controlling the network structure for making new functionality from EP. Indeed, the new modified EP represented as liquid crystalline epoxy (LCE) is spotlighted as an enabling technology for producing novel functionalities, which cannot be obtained from the conventional EPs, by replacing the random network structure to oriented one. In this paper, we review current progress in the field of LCEs and their application for the highly thermal conductive composite materials.