Thermal Conductivity Of Epoxy Composites Research Articles

Thermal conductivity of epoxy composites modified by microspheric molybdenum disulfide

In order to improve the thermal conductivity of epoxy resins (EP) without damaging their dielectric properties, a kind of molybdenum disulfide with microspheres structure (S-MoS2) was used as modifiers to add into EP matrix, which were prepared via the surfactant promoting hydrothermal process, and a new kind of S-MoS2/EP composites was finally obtained. The morphology of the prepared S-MoS2 was observed by X-ray diffraction (XRD) scanning electron microscopy (SEM), while the influence of different S-MoS2 loading on the dielectric properties, thermal conductivity and thermal resistance of S-MoS2/EP composites was also researched. The results suggested that the reasonable content of S-MoS2 can highly improve the thermal conductivity of S-MoS2/EP, which can be attributed to the excellent thermal resistant and uniform dispersion of S-MoS2 in EP matrix.

Enhanced thermal conductivity of epoxy composites reinforced with oriented polydopamine-graphene foam complexed by metal ions

Although graphene has aroused considerable interest in the thermal conductive enhancement of polymer composites for its superb intrinsic thermal conductivity, the enhancement efficiency is still limited by its production-induced defects, misalignment and intense phonon interface scattering. Herein, the three-dimensional (3D) polydopamine-graphene foam (PGF) with high orientation and good interfacial bonding has been prepared by electro-exfoliation, surface modification and unidirectional-freezing. This unique structure imparts excellent thermal conductivity, electrical insulation and good mechanical property to the PGF/epoxy (PGF/EP) composite. The highly arranged and compact stacked PDA-graphene sheets bound by metal ions provide heat conduction paths for effective phonon transport within the matrix. The manufactured PGF/EP shows enhanced through-plane thermal conductivity of 3.48 W/m·K with 3.02 vol% of PGF, excellent surface & volume electrical resistivity (2.7 × 1011 Ω and 1.65 × 1011 Ω·cm) and high mechanical strength (82.74 MPa), as well as the outstanding heat dissipation performance. Therefore, the PGF/EP composites prepared in the present study have a broad application prospect in advanced electronic packaging materials.

Large‐scale plasma grafts voltage stabilizer on hexagonal boron nitride for improving electrical insulation and thermal conductivity of epoxy composite

AbstractBetter electrical insulation and thermal management are both urgently required in integrated power semiconductors. Electrical insulation epoxy encapsulation suffers from poor heat conduction, which has increasingly become a bottleneck of power semiconductors integration. Although incorporating high thermal conductivity ceramics, such as hexagonal boron nitride (hBN), aluminium nitride etc. into epoxy promotes the thermal conductivity, the eco‐friendly scalable fabrication of these composites with sufficient electrical breakdown strength remains a formidable challenge. Suitable voltage stabilizers are known to provide additional benefits to breakdown strength. Herein, a high‐throughput approach combining plasma with roll‐to‐roll was developed. The voltage stabilizer (acetophenone) was grafted on interfaces between hBN and epoxy matrix through plasma. The high‐energy electrons are consumed by the grafted interface, which leads to the significant suppression of partial discharge in Epoxy/hBN. Meanwhile, interfacial phonon scattering is repaired by grafting. Therefore, the epoxy composite concurrently exhibits improved breakdown strength (by 27.4%) and thermal conductivity (by 142.9%) at about 11.9 wt.% filler content, outperforming the pure epoxy. Consequently, a promising modification strategy for mass production is provided for the encapsulation materials in various high‐power‐density semiconductor devices.

Enhanced thermal conductivity of epoxy composites with ternary particle size through the use of hybrid polyhedral α-alumina oxide and aluminum nitride

With the continued trends toward electronic device miniaturization, functionalization, and increased integration, epoxy-based cost-effective polymer composites with excellent thermal conductivity, dielectric performance, and processability are in high demand for the thermal management of electronic devices. An effective and continuous thermal transport pathway for epoxy composites was constructed by using a ternary-particle-size system comprising 22 μm polyhedral α-alumina oxide (Al2O3-22), 3.0 μm aluminum nitride (AlN-3), and 0.35 μm polyhedral α-alumina oxide (Al2O3-03). A distinctly high thermal conductivity (4.27 W/(m·K) and lower viscosity (35.28 Pa·s) were acquired using the ternary filler comprising 61.00 wt% Al2O3-22, 10.76 wt% AlN-3, and 6.24 wt% Al2O3-03. Meanwhile, the epoxy composites exhibited excellent thermo-mechanical properties, thermal stability, and dielectric performance. This work presents an easy and cost-effective approach for preparing highly thermally conductive and low-dielectric-performance polymer-based composites that can be widely used for the thermal management of electronic devices in the 5G era.

Aligning diamond particles inside BN honeycomb for significantly improving thermal conductivity of epoxy composite

Construction of interconnected heat conductive network in polymer is essential to effectively transport heat in thermal management materials. Due to synergistic effect, hybrid fillers are increasingly utilized in composites for higher thermal conductivity, but how to achieve better enhancement is still an open problem. In this paper, a pod-like 3D interconnected heat percolation network was obtained by aligning diamond inside boron nitride (BN) honeycomb. The BN honeycomb used as secondary templets was prepared by ice template method. Subsequently, the epoxy (EP) and diamonds were filled into it simultaneously by vacuum infiltration. SEM and computed tomography results demonstrated that highly ordered thermal conductive channels have been constructed. When the content of BN is 7 vol% and diamond is 12 vol%, the thermal conductivity of the composite is as high as 2.720 W/(m·K), which is 12.5 and 5.8 times higher than that of pure EP and randomly mixed sample, respectively. To better understand the enhance mechanism, through the parallel structural model calculations, the effective thermal conductivity of the local tightly packed diamond part was increased from 1.210 W/(m·K) to 11.318 W/(m·K) in the composite. The findings suggested that the bridging effect of BN wall on connecting diamond particles also contributed to enhanced property of the composite. This study offers a novel strategy for obtaining higher thermal conductivity with low filler loading in hybrid composites.

Optimization of mechanical properties of recycled polyurethane waste microfiller epoxy composites using grey relational analysis and taguchi method

Mechanical properties and thermal conductivity of epoxy composites reinforced with recycled clamshell container waste as a micro filler (RCCF) were studied. The studies have been carried out to identify the influence of the two variables, the heating time periods (HT) within the range of 2, 4, 6 min., and wt % within the range of 1 %, 2 %, 4 % of recycled clamshell container waste that has been used as a reinforcing filler of epoxy composites. Recycling polyurethane waste aims to control and maintain a pollution-free environment, which is currently considered a difficult issue in addition to achieving low-cost aspects in preparing the composites. According to the method of no-combustion heating, the clamshell waste was converted from the natural plastic state into solids that were later made into 75 μm micro filler by grinding. Composites were ranked using grey relational analysis (GRA). The effect of each control parameter on response variables was analyzed by the Taguchi method. Using MINITAB 19 software, regression equations were obtained for each variable of mechanical properties and thermal conductivity to predict the properties of epoxy composites. The results of the addition of recycled clamshell container waste to epoxy resin show an improvement in the mechanical properties and thermal conductivity of the composites. The optimal value of the two factors was at HT2wt2, i.e. HT and wt % of 4 min and 2 %, respectively. The optimization values for the bending strength, impact strength, tensile strength, stiffness and thermal conductivity are 68.2 MPa, 10.348 kJ/m2, 21.08 MPa, 80 Shore D and 0.504 W/m·C°, respectively. The proposed Taguchi methodology based on grey relational analysis has been shown to be effective in solving multi-feature decision-making problems.

The Investigation of the Effect of Filler Sizes in 3D-BN Skeletons on Thermal Conductivity of Epoxy-Based Composites.

Thermally conductive and electrically insulating materials have attracted much attention due to their applications in the field of microelectronics, but through-plane thermal conductivity of materials is still low at present. In this paper, a simple and environmentally friendly strategy is proposed to improve the through-plane thermal conductivity of epoxy composites using a 3D boron nitride (3D-BN) framework. In addition, the effect of filler sizes in 3D-BN skeletons on thermal conductivity was investigated. The epoxy composite with larger BN in lateral size showed a higher through-plane thermal conductivity of 2.01 W/m·K and maintained a low dielectric constant of 3.7 and a dielectric loss of 0.006 at 50 Hz, making it desirable for the application in microelectronic devices.

Amino functionalized boron nitride and enhanced thermal conductivity of epoxy composites via combining mixed sizes of fillers

With the emergence of 5G communication and the rapid development of the microelectronics industry, the heat dissipation of high power circuits has become quite an important issue. Along these lines, the thermal conductivity distribution of the electronic packaging materials, which plays a key role in the protecting circuits, requires urgent improvement. In this study, amino-functional boron nitride nanosheets (BNNS) were prepared by employing ball milling boron nitride with urea (aqueous solution) as agents. Then, the epoxy composites filled with large size pristine boron nitride (pBN) and small size functional boron nitride were fabricated by using the wet ball-milling (wBN) technique. The acquired results indicate that the thermal conductivity property of the pBN/wBN/epoxy composites with pBN/wBN ratio of 2.5/7.5 can reach the value of 0.386 W/mK, which is 96% higher than that of pure epoxy. Meanwhile, the measured value is superior from both the pBN/epoxy and wBN/epoxy composites with the same filling amount. This effect can be attributed to the efficient construction of the fillers network and thermal conduction path. Within the epoxy matrix, wBN can fill the pores between pBN and form a denser filler network. In addition, the amino-functional groups grafted with wBN result in their enhanced dispersion within the epoxy matrix that leads to a more stronger interfacial effect. Our approach provides useful insights in understanding the incorporation mechanisms of fillers in polymers, and thereby enhancing their potential applications.

The Dielectric Properties and Thermal Conductivities of Epoxy Composites Reinforced by Titanium Dioxide

To improve the dielectric properties and thermal conductivities of epoxy resins (EP), titanium dioxide superfine powders with microspheres structure (S-TiO2) were prepared via a hydrothermal process based on the sodium dodecyl benzene sulfonate and hydroxyl silicate. The different content of S-TiO2 was then employed as modifiers to add into EP resin to prepare the S-TiO2/EP composites. The structure and morphology of the prepared S-TiO2 was observed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and influences of different addition of S-TiO2 on the thermal conductivity of S-TiO2/EP composites are researched, while their dielectric constant and dielectric loss are also studied. The results suggested that the reasonable content of S-TiO2 can endow the S-TiO2/EP composites with higher dielectric constant without excessive increase their dielectric loss even under the high frequency. Furthermore, the thermal conductivity of S-TiO2/EP are also be improved, which can be attributed to the good thermal conductivity of S-TiO2 itself and the thermal conductivity path formed by S-TiO2 inside the EP matrix.

Enhanced thermal conductivity of epoxy composites by constructing thermal conduction networks via adding hybrid alumina filler

AbstractHigh thermal conductivity of polymer composites could be achieved through constructing 3D continuous thermally conductive networks into polymer composites. Herein, we demonstrate a simple, effective method to optimize the segregated alumina networks by using ternary mixture of alumina particles with different diameter ratios (5.8 μm + 2.6 μm + 0.5 μm) at the fixed total content of 60 wt% via conventional melt blending method. The thermal properties of epoxy composites were investigated as a function of the weight fraction and particle size of alumina particles. The thermal conductivity (TC) values of composites with coarse fillers (13.2 μm) are in agreement with Agari model at high filler loading (57 ~ 67 wt%). And the value of C2 was ~0.949 (close to 1), indicating that the formation of heat conduction paths in the composites. The addition of 60 wt% smaller fillers (2.6 μm) facilitates a higher interaction degree between the polymer/fillers, consequently, leads to a higher Tg of 147.8°C. A high TC of 1.109 W m−1 K−1 is achieved as the ratio of alumina filler with different particle sizes is 7/2/1, corresponding to a TC enhancement of 23%–32% compared to the composites with a single particle size filler. A suitable proportion of hybrid fillers is crucial for constructing three‐dimension continuous network, in which nano‐particles filled between the micro‐particles could increase the particle‐to‐particle connectivity.

Fabrication of EVA connected 3D BN network for enhancing the thermal conductivity of epoxy composites

Highly thermo-conductive polymer-based composites have attracted extensive attention in the field of electronic and heat exchange. However, it is still challenging to obtain a favorable thermal conductivity enhancement at low filler loading by directly using commercial fillers. Here, a lightweight and mechanically strong 3D hexagonal boron nitride (BN) network is prepared using BN as basic assembly unit. The prepared 3D framework displays a sponge-like structure in which the BN microplates act as a skeleton and poly (ethylene-co-vinyl acetate) (EVA) act as adhesive. Afterward, epoxy resin is then infiltrated into the 3D BN skeleton to manufacture the composites with the assistance of vacuum planetary stirring. High thermal conductivity of 1.85 W m−1 K−1 is achieved at low BN loading of 16.8 vol%, which is equivalent to a thermal conductivity enhancement of 820% in comparison with pure epoxy resin. The prepared epoxy composites possess excellent thermal management capabilities, showing large potential applications in advanced electronic devices.

The synergistic effect of irregular alumina and round plates boron nitride binary‐particle system on the thermal conductivity of epoxy composites

AbstractAs the main encapsulation material, epoxy resin has an urgent need to obtain higher thermal conductivity. So how to improve the thermal conductivity of epoxy resin is very important. In this work, a novel strategy is proposed that the irregular alumina (i‐Al2O3) and the round plate boron nitride (h‐BN) are integrated into epoxy resin to enhance the thermal conductivity. When the total amount of filler is 40%, and the volume ratio of auxiliary filler h‐BN and the basic filler i‐Al2O3 is 6: 34，The thermal conductivity of the epoxy composites is significantly increased 709% higher than that of pure epoxy resin. The roles of the main filler i‐Al2O3 and the auxiliary filler h‐BN in epoxy composites system were investigated. A possible mechanism was established that the h‐BN connects i‐Al2O3 to generate the heat conduction network. The blending of irregular particles and round plate method proposed in this work is a new avenue, which meets the need of industrialized design and fabricating, making an achievement of obtaining a kind of epoxy composites with a high thermal conductivity and excellent comprehensive properties.

Simple large-scale method of recycled graphene films vertical arrangement for superhigh through-plane thermal conductivity of epoxy composites

Highly thermal conductive polymer-based materials are essential for modern microelectronic devices. However, conventional thermal conductive polymer-based composites exhibit constrained thermal conductivity even at a high content of highly thermal conductive fillers due to the lack of significant thermal conductive paths. In this work, effective thermal conductive paths were constructed with macro recycled graphene film fragments that were vertically arranged by a method of area restricting in the vertical direction under mechanical force. The resulting composites with vertically arranged structure displayed highly through-plane thermal conductivity of 20.97 W m−1 K−1 at 32.63 wt% graphene film fragments loading. Another three contrast experiments in different adding ways of fillers were as well accomplished to confirm the excellent vertically arranged structure. This study not only provides a simple way to obtain highly thermal conductive composites but also offers a strategy of making full use of wastes from industrial applications. The facile method for obtaining the superhigh though-plane thermal conductivity enlightens us to practical application. The recycled graphene films as millimeter-particles in this study can be expanded to other millimeter-particles arrangements. The mechanical force used for vertically arranged structure can be broadened to other forces such as vacuum or hydraulic pressure.

Polyethylene glycol covalently modified the corroded hexagonal boron nitride to improve the thermal conductivity of epoxy composites

The wide application of hexagonal boron nitride (h-BN) is limited because it is difficult to achieve functionalization with trace amounts of active groups. We noticed that a considerable amount of hydroxyl and amino groups are generated after mixing h-BN and sulfonyl chloride at room temperature for 48 h. Subsequently, these active groups are used to react with furoyl chloride, and polyethylene glycol (PEG) is introduced through a mild Diels-Alder reaction to improve its dispersibility and compatibility with epoxy resin matrix. The modified h-BN are characterized by Fourier transform infrared (FT-IR), thermogravimetric (TGA), and transmission electron microscopy (TEM) to investigate the covalent modification results and its structure. Finally, the thermal conductivity of epoxy composites with different filler content show that the h-BN covalently modified by PEG can improve the thermal conductivity of the composites.

The desirable dielectric properties and high thermal conductivity of epoxy composites with the cobweb-structured SiCnw–SiO2–NH2 hybrids

The desirable dielectric properties and high thermal conductivity of epoxy composites with the cobweb-structured SiCnw–SiO2–NH2 hybrids

Ultrahigh Thermal Conductivity of Epoxy Composites with Hybrid Carbon Fiber and Graphene Filler

Ultrahigh Thermal Conductivity of Epoxy Composites with Hybrid Carbon Fiber and Graphene Filler

Surface NH2-functionalized by C doping of boron nitride nanotube to improve the thermal conductivity of epoxy composites

To reduce the interfacial thermal resistance between boron nitride nanotubes (BNNTs) and epoxy resin, we report a novel method to obtain NH2-functionalized BNNTs with a perfect crystal structure by C doping to construct chemically active sites on the BNNT surface (BNNT-A), and compare it with the conventional method of NH2-functionalized BNNTs by breaking the B–N bond (BNNT-B). The results show that the insulation properties and thermal conductivity of BNNT-A were better than those of BNNT-B. When the NH2-functionalized ratio was 5%, the thermal conductivity of BNNT-A was improved by 12.21 W/(m·K) compared with that of BNNT-B. NH2 functionalization had little effect on the insulation properties of BNNT-A/epoxy resin (BNNT-A-EP), and BNNT-B/epoxy resin (BNNT-B-EP) comparing with BNNT/epoxy resin (BNNT-EP). The thermal conductivity of BNNT-A-EP was 2.52 W/(m·K), which was improved by 23.5% and 77.5% compared with BNNT-B-EP and BNNT-EP, respectively. In addition, the volume change rate of BNNT-A-EP was reduced by 27.6% and 50% relative to BNNT-EP and BNNT-B-EP. The functionalization of NH2 on the surface of BNNTs by C doping can establish an effective heat transfer "bridge" between BNNTs and epoxy resin, which is beneficial for improving the thermal conductivity of epoxy composites. This work presents a strong potential method to reduce the interfacial thermal resistance of electronic packaging materials.

Ultrahigh thermal conductivity of epoxy composites based on curling bioinspired functionalized graphite films for thermal management application

Unsatisfactory thermal conductive network (TCN) and poor heat conduction interface have limited thermal conductivity (TC) enhancement in the polymeric composites. In this study, inspired by mussels and a Chinese delicacy called the Hanamaki, a facile and environmental strategy is developed to prepare hierarchically ordered graphite film strips@polydopamine/epoxy (GFs@PDA/EP) composites. Organized TCNs and an optimized interface were constructed and thus an ultrahigh TC of GFs/EP (899.44 ± 18.51 W m−1 K−1) in perpendicular direction was obtained. Structural analysis and heat-transfer passages model suggests that superior TCNs were constructed and the designed structure is conducive for heat conduction in the perpendicular direction. Moreover, the interfacial bonding of GFs@PDA with EP matrix contributes to the remarkable enhancement of TC with increasing of PDA coverage. A decrease of ~43 °C in the thermal management experiment of LED chips indicated that it most likely becomes a good candidate in electronic device-cooling application.

Carbon nano-onions as a nanofiller for enhancing thermal conductivity of epoxy composites

Carbon nano-onions (CNOs) are a relatively new member in zero-dimensional carbon nanomaterials. Each constituent unit of CNOs is a multi-layer concentric spherical structure composed of multiple fullerene-like carbon spheres. CNOs are widely used for electronic components applications due to their large specific surface area and high electric conductivity. But a few works of CNOs on thermal conduction property in electronic device applications were studied. Therefore, we prepared the CNOs/epoxy composites by blending and casting method, and investigated the thermal conduction mechanism of CNOs in the epoxy matrix. The results show that the thermal conductivity of epoxy composite with 30 wt% CNOs loading reaches 0.59 W m−1 K−1 due to the formation of an effective thermal network of CNOs in epoxy resin, increasing by 320% in comparison with neat epoxy. In view of excellent thermal conduction performance, CNOs may be enable used as thermal conductive filler for the thermal management of electronic components.

Remarkable Thermal Conductivity of Epoxy Composites Filled with Boron Nitride and Cured under Pressure.

This work demonstrates that the application of even moderate pressures during cure can result in a remarkable enhancement of the thermal conductivity of composites of epoxy and boron nitride (BN). Two systems have been used: epoxy-thiol and epoxy–diamine composites, filled with BN particles of different sizes and types: 2, 30 and 180 μm platelets and 120 μm agglomerates. Using measurements of density and thermal conductivity, samples cured under pressures of 175 kPa and 2 MPa are compared with the same compositions cured at ambient pressure. The thermal conductivity increases for all samples cured under pressure, but the mechanism responsible depends on the composite system: For epoxy–diamine composites, the increase results principally from a reduction in the void content; for the epoxy–thiol system with BN platelets, the increase results from an improved matrix-particle interface; for the epoxy–thiol system with BN agglomerates, which has a thermal conductivity greater than 10 W/mK at 44.7 vol.% filler content, the agglomerates are deformed to give a significantly increased area of contact. These results indicate that curing under pressure is an effective means of achieving high conductivity in epoxy-BN composites.