Simple and Consecutive Melt Extrusion Method to Fabricate Thermally Conductive Composites with Highly Oriented Boron Nitrides

Feng

J of Applied Polymer Sci

et al. 2020

A scalable strategy to fabricate thermally conductive but electrically insulating polymer composites was urgently required in various applications including heat exchangers and electronic packages. In this work, multilayered ultrahigh molecular weight polyethylene (UHMWPE)/natural graphite (NG)/boron nitride (BN) composites were prepared by hot compressing the UHMWPE/NG layers and UHMWPE/BN layers alternately. Taking advantage of the internal properties of NG and BN fillers, the UHMWPE/NG layers played a decisive role in enhancing thermal conductivity (TC), while the UHMWPE/BN layers effectively blocked the electrically conductive pathways without affecting the thermal conductive pathways. The in-plane TC, electrical insulation, and heat spreading ability of multilayered UHMWPE/NG/BN composites increased with the increasing layer numbers. At the total fillers loading of 40 wt%, the in-plane TC of multilayered UHMWPE/NG/BN composites with nine layers was markedly improved to 6.319 Wm −1 K −1 , outperforming UHMWPE/BN (4.735 Wm −1 K −1) and pure UHMWPE (0.305 Wm −1 K −1) by 33.45% and 1971.80%, respectively. Meanwhile, the UHMWPE/NG/BN composites still maintained an excellent electrically insulating property (volume resis-tance~5.40×10 14 Ω cm; breakdown voltage~1.52 kV/mm). Moreover, the multilayered UHMWPE/NG/BN composites also exhibited surpassing heat dissipation capability and mechanical properties. Our results provided an effective method to fabricate highly thermal conductive and electrical insulating composites. K E Y W O R D S applications, composites, thermal properties, molding 1 | INTRODUCTION Owing to the rapidly escalation of power densities and integration in electronic components, heat dissipation has become a critical issue to protect electronics from overheating. Polymer-based composites are widely used in many fields for their excellent processability, lightweight, low cost, and outstanding chemical stability. 1-3

Section: Introductionmentioning

confidence: 99%

Multilayered ultrahigh molecular weight polyethylene/natural graphite/boron nitride composites with enhanced thermal conductivity and electrical insulation by hot compression

Feng

J of Applied Polymer Sci

et al. 2020

“…As a result of the higher degree of swelling obtained in filaments extruded with the conical output extrusion die, ABS matrix moves to the surface of the filament creating a thin insulating layer, with the consequent decrease in electrical conductivity. Additionally, orientation of the GNPs along the extrusion axis occurs, and this is more effective when using higher extrusion speed rates and higher temperatures, i.e., lower viscosities [28][29][30].…”

Section: Influence Of 3d Printing Operational Parameters On the Electmentioning

confidence: 99%

Influence of Manufacturing Parameters and Post Processing on the Electrical Conductivity of Extrusion-Based 3D Printed Nanocomposite Parts

et al. 2020

The influence of manufacturing parameters of filament extrusion and extrusion-based Additive Manufacturing (AM), as well as different post processing techniques, on the electrical conductivity of 3D printed parts of graphene nanoplatelets (GNP)-reinforced acrylonitrile butadiene styrene (ABS) has been analyzed. The key role of the manufacturing parameters to obtain electrically conductive filaments and 3D printed parts has been demonstrated. Results have shown that an increase in extrusion speed, as well as lower land lengths, induces higher extrudate swelling, with the consequent reduction of the electrical conductivity. Additionally, filaments with lower diameter values, which result in a higher surface-to-cross-section ratio, have considerably lower electrical conductivities. These factors tune the values of the volume and surface electrical conductivity between 10−4–100 S/m and 10−8–10−3 S/sq, respectively. The volume and surface electrical conductivity considerably diminished after 3D printing. They increased when using higher printing layer thickness and width and were ranging between 10−7–10−4 S/m and 10−8–10−5 S/sq, respectively. This is attributed to the higher cross section area of the individual printed lines. The effect of different post processing (acetone vapor polishing, plasma and neosanding, which is a novel finishing process) on 3D printed parts in morphology and surface electrical conductivity was also analyzed.

J of Applied Polymer Sci

“…In addition, the BN was horizontally oriented under the external force field of the processing, which greatly reduced the thermal conductivity in the vertical direction. 32 Compared with the platelet-like fillers, the adding of spherical filler does not induce to large increase the viscosity of polymer composites due to small contact area between spherical fillers, even at very high loading. 33 Can flake boron nitride be combined with a kind of spherical filler?…”

Section: Introductionmentioning

confidence: 99%

“…The increase of viscosity will limit the amount of h‐BN in polymer, which results in limiting the improvement of thermal conductivity of composites. In addition, the BN was horizontally oriented under the external force field of the processing, which greatly reduced the thermal conductivity in the vertical direction 32 . Compared with the platelet‐like fillers, the adding of spherical filler does not induce to large increase the viscosity of polymer composites due to small contact area between spherical fillers, even at very high loading 33 .…”

Section: Introductionmentioning

confidence: 99%

Spherical hybrid filler BN@Al₂O₃ via chemical adhesive for enhancing thermal conductivity and processability of silicon rubber

Guan

Chen

et al. 2021

Hexagonal boron nitride (h-BN) is an ideal candidate material for electrical and electronic systems due to its excellent performance. However, the addition of platelet-like h-BN leads to a dramatic increase of viscosity of composites and anisotropic thermal conductivity of composites. Herein, modified h-BN (m-BN) was coated onto spherical α-Al 2 O 3 via chemical adhesive, and coreshell structured hybrid spherical filler (m-BN@Al 2 O 3 ) was prepared. Furthermore, the microstructure, rheology, mechanical properties, and thermal conductivity of hybrid filler/polydimethylsiloxane (PDMS) were studied. At 60 vol % filler loading, the thermal conductivity of m-BN@Al 2 O 3 /PDMS is up to 2.23 WÁm À1 ÁK À1 , which is 86% higher than that of Al 2 O 3 /PDMS and the ratio of in-plane diffusivity to through-plane diffusivity decreases from 2.0 to 1.0. At meanwhile, the viscosity of m-BN@Al 2 O 3 /PDMS is about one fourth of the viscosity of m-BN/Al 2 O 3 /PDMS. This simple and versatile strategy opens a pavement for enhancing the thermal conductivity of polymer and has great potential in high-frequency communication.