Highly anisotropic thermal conductivity of mesogenic epoxy resin film through orientation control

Tang, Ning; Tanaka, Shingo; Takezawa, Yoshitaka; Kanie, Kiyoshi

doi:10.1002/app.51396

Cited by 10 publications

(10 citation statements)

References 48 publications

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“…The thermal conductivity of mica tape is generally reflected by its thermal conductivity 33–37 . Thermal conductivity refers to the heat transmitted by the material with a fixed thickness per unit area per unit time and it is the inherent property of the material 38–43 .…”

Section: Resultsmentioning

confidence: 99%

“…The thermal conductivity of mica tape is generally reflected by its thermal conductivity. [33][34][35][36][37] Thermal conductivity refers to the heat transmitted by the material with a fixed thickness per unit area per unit time and it is the inherent property of the material. [38][39][40][41][42][43] Figure 5 shows the variation of thermal conductivity of high thermal conductivity mica tape with coating mass fraction and temperature.…”

Section: Thermal Properties Of Mica Tapementioning

confidence: 99%

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Enhanced thermal conductivity and insulation properties of mica tape with BN coating via electrostatic spraying technology

Feng

Yang

et al. 2022

J of Applied Polymer Sci

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The bottleneck problem of the development of high‐voltage motors to a larger capacity can be solved if the thermal conductivity is improved without sacrificing the insulation characteristics of the main insulation material. In this paper, a spraying technology based on electrospinning is proposed that can evenly spray boron nitride (BN) with high thermal conductivity onto the surface of mica tape. With the increase in BN content, the insulation and thermal conductivity of mica tape are optimized to varying degrees. When the BN content reaches 2.25 wt%, the in‐plane conductivity increases from 1.6 to 2.7 w/(m K), while the out‐of‐plane conductivity increases from 0.17 to 0.26 w/(m K). Additionally, the direct‐current (DC) breakdown strength has increased from 90.6 to 96.9 kV/mm and the dielectric constant and dielectric loss are almost unchanged. Finally, through simulation verification, if the modified mica tape is applied to the main insulation of a synchronous motor, the operating temperature of the motor insulation will be reduced from 73.5 to 66.1°C. This study provides a new research idea for the preparation of high thermal conductivity insulating materials.

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Section: Resultsmentioning

confidence: 99%

Section: Thermal Properties Of Mica Tapementioning

confidence: 99%

Enhanced thermal conductivity and insulation properties of mica tape with BN coating via electrostatic spraying technology

Feng

Yang

et al. 2022

J of Applied Polymer Sci

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“…Therefore, to reduce phonon scattering and achieve high thermal conductivity, it is effective to form a highly ordered higher-order structure inside the polymer by self-alignment of the mesogen backbone, ,− and then to design molecules that increase the cross-linking density by selecting a curing agent . Recently, a research study utilized a mesogen epoxy resin film alone, without the addition of a thermally conductive ceramic filler, and achieved a thermal conductivity of 10 W/(m·K) . Although thermoplastic polymers exhibit a significant decrease in the thermal conductivity above Tg, thermosetting polymers experience a minor decrease in thermal conductivity.…”

Section: Introductionmentioning

confidence: 99%

Higher-Order Structural Analysis of a Transparent and Flexible High Thermal Conductive Liquid Crystalline Elastomer Sheet and Its Composite

Takezawa,

Furukawa,

Nachimuthu

et al. 2024

ACS Omega

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Transparency, flexibility, and high thermal conductivity are trade-offs. Specifically, we have investigated a cross-linked acrylic liquid crystal elastomer (LCE) that exhibits both transparency and flexibility while maintaining a high level of thermal conductivity. The transparent monodomain LCE sheet was achieved through a process of stretching an initially opaque polydomain sheet to 80% elongation and subsequently subjecting it to photocuring. The thermal conductivity in the stretching direction (x) of the monodomain LCE sheet was found to be 1.8 times higher than that of the prestretched polydomain sheet, consistent with findings from previous studies. However, in the orthogonal direction (y) to the stretching (x) direction, the thermal conductivity exhibited an even higher value, being 1.7 times greater than in the x-direction, with a value of 3.0 W/(m•K). This unique observation prompted us to conduct further investigation through higher-order structural analysis of these LCE sheets using 2D wide-angle X-ray scattering (WAXS) analysis. In the transparent sheet, the LCE molecules were aligned in the sheet in the stretching x-direction (monodomain structure) for the out-of-plane direction. However, in the inplane x-direction, the molecular plane spacing exhibited random orientation at a period of 0.45 nm. In contrast, within the ydirection of the inner layer, the molecular plane spacing exhibited a uniaxial horizontal orientation at the same period length as in the x-direction. The heat energy entering into the y-direction once spreads to the x-direction, but it was considered that the reason for the higher thermal conductivity to the y-direction would be forming covalent bonds that function as new heat transmission paths, in the direction intersecting to the x-direction during photocuring. Therefore, we concluded that the synergistic effect of the high level of the ordered inner structure and covalent bonding structure due to cross-linking in the y-direction contributes to its higher thermal conductivity compared to that in the x-direction, which exhibits a random in-plane structure. Additionally, we have fabricated an LCE composite sheet filled with 75 vol % of alumina particles using a polydomain-type LCE as the base material. The composite sheet exhibits remarkable thermal conductivity in the thickness direction, measuring at 9.8 W/(m•K), while maintaining a flexibility characterized by an elastic modulus of 70 MPa. This thermal conductivity surpasses that of a nonmesogenic acrylic composite sheet with identical alumina particle filling, which measured at 3.9 W/(m•K), more than twice as much. The presence of the mesogen skeleton has been demonstrated to enhance heat transfer, even within soft composites, by facilitating the formation of an ordered structure.

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“…These properties meet the component requirements of electric and electronic devices. Among ERs, liquid crystalline (LC) ERs have been intensively synthesized − and investigated because of their outstanding properties such as high thermal conductivity, − fractural toughness, − and moisture resistance, in addition to the properties of general LCs or amorphous ERs. Particularly, the high thermal conductivity of LCERs has gathered attention because electrical and electronic devices progress in downsizing, integrating, and multi-functionalizing, and the heat accumulated in the devices has become a critical issue.…”

Section: Introductionmentioning

confidence: 99%

Forming a Homeotropic SmA Structure of Liquid Crystalline Epoxy Resin on an Amine-Modified Surface

Tanaka,

Takezawa,

Kanie

et al. 2023

ACS Omega

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The molecular orientation of a liquid crystalline (LC) epoxy resin (LCER) on silane coupling surfaces of amorphous soda-lime-silica glass substrates was investigated. The LC epoxy monomer on the silane coupling surfaces of the substrates was revealed to form a smectic A (SmA) phase with planar alignments because of the relatively low surface free energy. An LCER with a curing agent, however, formed a homeotropically aligned SmA structure by curing on a substrate surface modified using a silane coupling agent with amino groups. This formation of homeotropic alignment was considered due to the attribution of the reaction between the amino group on the surface of the substrate and the epoxy group of the LCER. The homeotropic alignment had a relatively high orientation parameter of 0.95. Therefore, it is expected to possess high thermal conductivity and be applied as high-thermal-conductivity adhesives or packaging materials for electrical and electronic devices.

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Highly anisotropic thermal conductivity of mesogenic epoxy resin film through orientation control

Cited by 10 publications

References 48 publications

Enhanced thermal conductivity and insulation properties of mica tape with BN coating via electrostatic spraying technology

Enhanced thermal conductivity and insulation properties of mica tape with BN coating via electrostatic spraying technology

Higher-Order Structural Analysis of a Transparent and Flexible High Thermal Conductive Liquid Crystalline Elastomer Sheet and Its Composite

Forming a Homeotropic SmA Structure of Liquid Crystalline Epoxy Resin on an Amine-Modified Surface

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