Tremendous investigations have been recently conducted to increase the thermal conductivity (TC) of nanofiller filled thermoplastic composites. However, the agglomeration of nanofillers limits their ...loading and is a bottleneck to further increase the TC of composites. In this work, a preparation technique combining the benefits of both solution mixing and melt blending is proposed, with which high loading and good dispersion of graphene sheets (GSs) filled polyamide 6 (PA6) matrix composites are achieved. Noteworthily, the through-plane TC of the composites reaches 3.55 W m−1 K−1 with 20 wt% GSs, corresponding to a TC enhancement of 1167% compared to pure PA6. The excellent performance can be attributed to high loading and uniform dispersion of GSs, which facilitate the formation of thermally conductive network for efficient heat transfer. An effective medium theory model by taking the filler-to-matrix and filler-to-filler interfacial effects into consideration is also proposed to perceive the behind mechanism. The theoretical calculation agrees well with our experimental results. Moreover, we find the Young’s modulus of the composite increases significantly and the tensile strength nearly remains unchanged even at a GSs filler loading of 20 wt%. The results provide an effective and facile route for developing low-cost and highly conductive thermoplastic composites.
With the rapid development of the electronic industry, the requirements for packaging materials with high thermal conductivity (TC) are getting higher and higher. Epoxy is widely used as package ...material for electronic package applications. But it's intrinsic TC can't meets the increasing demands. Adding high TC graphene into epoxy matrix is a proper way to reinforce epoxy composites. This review focuses on the filler modification, preparation process and thermal properties of graphene-filled epoxy resin composites. Different ways of covalent and non-covalent modification methods are discussed. The various kinds of graphene coating layer are also summarized. Then we analysis the hybrid filler system in epoxy composite. We hope this review will provide guidance for the development and application of graphene-filled epoxy resin composites.
Attributed to the intense development and complexity in electronic devices, energy dissipation is becoming more essential nowadays. The carbonaceous materials particularly graphene (Gr)-based thermal ...interface materials (TIMs) are exceptional in heat management. However, because of the anisotropic behavior of Gr in composites, the TIMs having outstanding through-plane thermal conductivity (
⊥
TC) are needed to fulfill the upcoming innovation in numerous devices. In order to achieve this, herein, nano-urethane linkage-based modified Gr and carbon fibers architecture termed as nanourethane linkage (NUL)-Gr/carbon fibers (CFs) is fabricated. Wherein, toluene diisocyanate is utilized to develop a novel but simple NUL to shape a new interface between graphene sheets. Interestingly, the prepared composite of NUL-Gr/CFs with polyvinylidene fluoride matrix shows outstanding performance in heat management. Owing to the unique structure of NUL-Gr/CFs, an unprecedented value of
⊥
TC (~ 7.96 W·m
−1
·K
−1
) is achieved at a low filler fraction of 13.8 wt.% which translates into an improvement of ~ 3,980% of pristine polymer. The achieved outcomes elucidate the significance of the covalent interaction between graphene sheets as well as strong bonding among graphene and matrix in the composites and manifest the potential of proposed NUL-Gr/CFs architecture for practical applications.
The power electronics industry has been actively seeking high temperature stable epoxy molding compound (EMC) materials that can meet the requirements for encapsulating future SiC chips operating at ...a temperature (250 °C) that exceeds the capability of current epoxy chemistry. This work provides a detailed evaluation of a high heat resistant cyanate ester (CE)/epoxidized cresol novolac (ECN) copolymer system with varied compositions regarding their high temperature performances. Owing to the novolac nature of ECN which provides a high crosslink density, it is found that the copolymers with a low CE concentration (25–33 mol%) are able to produce a comparable glass transition temperature (>230 °C) and decomposition temperature (T10%>400 °C) to those of the high CE formulations. Moreover, long-term high temperature (250 °C) storage test of reveals a less severe weight loss and blistering in the lower CE formulations. A distinguished degradation mechanism involving hydrolysis of unreacted cyanate groups in the high CE compositions was determined through various thermal and chemical analyses. It was concluded that the CE/ECN copolymers with low CE concentrations are promising candidates for the high temperature EMC formulation.
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•Curable cyanate ester (CE)/epoxidized cresol novolac (ECN) copolymers with varied compositions were prepared.•High glass transition temperature (>230 °C) and decomposition temperature (T10% > 400 °C) was achieved in low CE formulations.•High temperature (250 °C) aging revealed poor stability of high CE formulations due to several hydrolysis degradation.•Overall, 25 mol%~33 mol% of CE concentration produced best copolymer for high temperature encapsulant applications.
Efficient thermal transportation in a preferred direction is highly favorable for thermal management issues. The combination of 3D printing and two-dimensional (2D) materials such as graphene, BN, ...and so on enables infinite possibilities for hierarchically aligned structure programming. In this work, we report the formation of the asymmetrically aligned structure of graphene filled thermoplastic polyurethane (TPU) composites during 3D printing process. The as-printed vertically aligned structure demonstrates a through-plane thermal conductivity (TC) up to 12 W m–1 K–1 at 45 wt % graphene content, which is ∼8 times of that of a horizontally printed structure and surpasses many of the traditional particle reinforced polymer composites. The superior TC is mainly attributed to the anisotropic structure design that benefited from the preferable degree of orientation of graphene and the multiscale dense structure realized by finely controlling the printing parameters. Finite element method (FEM) confirms the essential impact of anisotropic TC design for highly thermal conductive composites. This study provides an effective way to develop 3D printed graphene-based polymer composites for scalable thermal-related applications such as battery thermal management, electric packaging, and so on.
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•h-BN assembles into spherical aggregated BN (A-BN) assisted by the vortex flow.•The mechanism and operating conditions of A-BN formation are systematically studied.•A through-plane ...TC of 6.56 W/(mK) is achieved due to the formation of A-BN.•A-BN/AlN/SR composite demonstrates excellent heat dissipation performance as TIMs.
Thermal interface materials (TIMs) with high thermal conductivity and good insulation properties are in high demand for thermal management systems. Platelet-like materials such as BN and graphene usually orient horizontally in polymer composites, causing minor Through-plane thermal conductivity (TC) enhancement. Herein, aggregated BN (A-BN)/AlN/silicone rubber (SR) composites with enhanced through-plane TC are fabricated assisted by vortex flow during the planetary centrifugation process. It is found that BN platelets assembled into A-BN with spherical AlN as cores based on concentric vortex. Due to the formation of spherical A-BN, through-plane TC of as-prepared composites with 40 wt% BN and 45 wt% AlN is as high as 6.56 W/(m·K) while it is only 4.62 W/(m·K) for composites without A-BN. Such high TC should mainly be attributed to the large-sized spherical BN interconnected structure which constructs an efficient thermally conductive path in the through-plane direction. The heat dissipation evaluation test also demonstrates the excellent performance of the A-BN/AlN/SR composite. This work provides a facile strategy to produce large-sized BN agglomerates and gives insights into the vortex flow during the planetary centrifugation process.
To meet the increasing demands for effective heat management of electronic devices, a graphene-based polymeric composite is considered to be one of the candidate materials owing to the ultrahigh ...thermal conductivity (TC) of graphene. However, poor graphene dispersion, low quality of exfoliated graphene, and strong phonon scattering at the graphene/matrix interface restrict the heat dissipation ability of graphene-filled composites. Here, a facile and versatile approach to bond graphene foam (GF) with polydimethylsiloxane (PDMS) is proposed, and the corresponding composite with considerable improvement in TC and insulativity is fabricated. First, three-dimensional GF was coated with polydopamine (PDA) via π–π stack and functional groups from PDA reacted with 3-aminopropyltriethoxysilane (APTS). Then, the modified GF was compressed (c-GF) to enhance density and infiltrated with PDMS to get the c-GF/PDA/APTS/PDMS composite. As a result, these processes endow the composite with high TC of in-plane 28.77 W m–1 K–1 and out-of-plane 1.62 W m–1 K–1 at 11.62 wt % GF loading. Besides, the composite manifests obvious improvement in mechanical properties, thermal stability, and insulativity compared to neat PDMS and GF/PDMS composite. An attempt to use the composite for cooling a ceramic heater is found to be successful. Above results open a way for such composites to be applied for the heat management of electronic devices.
π-π stacking interface design strategy is proposed to prepare ultrathin and flexible water-borne polymer/sulfonated graphene nanosheets (S-GNS) composite by a facile self-assembly method in latex. ...The water-dispersible S-GNS was made by modifying the GNS with aryl diazonium salt. Styrene was introduced into water-borne polymer to form π-π stacking interaction with S-GNS. The composite shows good mechanical properties and high electromagnetic interference (EMI) shielding effectiveness (SE) in the X band (8.2–12.4 GHz). By Raman spectra, tensile tests, and simulation calculation, π-π stacking interaction is proved to be an effective interface bonding to enhance the mechanical properties. With a filler loading of 20 wt%, the tensile strength of composites is enhanced by 578%. The incorporation of 25 wt% S-GNS leads to a high EMI SE of 21.5 dB at 0.05 mm thickness, which remains unchanged after 1000 times bending. The specific SE/thickness (SSE/t) of the composite is as high as 2663 dB cm2/g, outperforming the ever reported materials with similar filler loading (25 wt%). The composite can be used as coating on the surfaces of solids, indicating the great potential for wide application.
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Flexible and highly filled conductive polymer composites with strong mechanical properties are highly desirable as electromagnetic interference (EMI) shielding and thermally conductive materials for ...human protection and wearable devices. Herein, a tough interface has been built up by the combination of polydopamine modification and pH triggered hydrogen bonding to prepare flexible and mechanically robust waterborne polyacrylate/graphene@polydopamine composites. Graphene was modified with polydopamine via an in-situ polymerization method. By adjusting the initial pH value in the film formation process, the transition from electrostatic repulsion to hydrogen bonding between graphene@polydopamine and polyacrylate was engineered for improving the mechanical properties. At optimal pH value, the maximum tensile strength of the composite is enhanced by 137% compared with that of neat polymer matrix. Moreover, the composite with filler loading of 20 wt% exhibits an EMI shielding effectiveness of 58 dB at 0.6 mm thickness and thermal conductivity of 1.68 W/m·K, respectively. The practical application of the composite film and composite coated leather also demonstrates their outstanding flexibility, EMI shielding, and heat dissipation performance, indicating their excellent potential as EMI shielding and thermally conductive materials in wide areas such as wearable devices, telecommunication systems, and human protection.
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With the increasing packaging density and multi-functionality, thermal management and electromagnetic pollution in electronic devices are crucial. In this work, we propose a novel method to in-situ ...grow hollow Fe3O4 sphere (h-Fe3O4, inner and outer diameter of 870 nm and 975 nm, respectively) onto three-dimensional graphene foam (GF) surface and then filled it with polydimethylsiloxane (PDMS) to fabricate nanocomposites with high electromagnetic interference shielding effectiveness (70.37 dB from 8.2 to 12.4 GHz) and thermal conductivity (28.12 ± 1.212 W m−1 K−1) at room temperature. Moreover, conductive networks inside composites show super-flexible performance with high electrical conductivity (84.02 ± 8.385 S cm−1). The effect of in-situ growth hollow Fe3O4 spheres in the enhancement of EMI SE has been demonstrated via comparing with different contents, morphologies and preparation processing. Besides, the mechanism of thermal conductivity has been investigated by FEM simulation and theoretical modeling. Finally, the usage of GF/h-Fe3O4/PDMS composites as thermal interface materials (TIMs) for chip cooling is proved to be successful, and the corresponding temperature under usage power density is accurately predicted. These comprehensive properties of GF/h-Fe3O4/PDMS composite open a potential application for next-generation TIMs in chip packaging.
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