Synchronously enhancing thermal conductivity and dielectric properties in epoxy composites via incorporation of functionalized boron nitride

Polymer-like dielectrics with superb thermal conductivity as well as high dielectric properties hold great promise for the modern electronic field. Nevertheless, integrating these properties into a single material simultaneously remains problematic due to their mutually limited physical connotations. In this study, we developed high-quality thermally conductive epoxy composites with excellent dielectric properties. This was achieved by incorporating surface-functionalized microscale hexagonal boron nitride (BN) along with N-[3-(Trimethoxysilyl)propyl]ethylene diamine (DN) and N-[3-(Trimethoxysilyl)propyl]aniline (PN). In the resulting epoxy composite, microscale BN serves as the primary building block for establishing the thermally conductive network, while silica particles act as bridges to regulate heat transfer and reduce interfacial phonon-scattering. The prepared composites were thoroughly examined across various filler contents (ranging from 10 to 80 wt%). Among them, the DNBN/epoxy composite exhibited higher thermal conductivity (in-plane: 47.03 W m-1 K-1) at 60 wt% filler content compared to BN/epoxy (39.40 W m-1 K-1) and PNBN/epoxy (33 W m-1 K-1) composites. These results highlight the usefulness of surface modification of BN in improving compatibility between fillers and epoxy, ultimately reducing composite viscosity. Furthermore, the DNBN/epoxy composite at 60 wt% demonstrated superb dielectric constant (∼6.15) without compromising on dissipation loss (∼0.06). The strategy adopted in this study offers significant insights into designing dielectric thermally conductive composites with superior performance outcomes.

Synergistic Improvement in the Thermal Conductivity of Hybrid Boron Nitride Nanotube/Nanosheet Epoxy Composites

Epoxy composites with excellent thermal properties are highly promising for thermal management applications in modern electronic devices. In this work, we report the enhancement of the thermal conductivity of two different nanocomposites, using epoxy resins LY564 (epoxy 1) and LY5052 (epoxy 2), by incorporating multiwalled boron nitride nanotubes (BNNT) and boron nitride nanosheets (BNNS) as fillers. The synergistic interaction between the 1D BNNT and 2D BNNS allows for improved thermal conductivity via several different mechanisms. The highest thermal conductivity was measured at a loading of 1/30 wt % of BNNT/BNNS, resulting in values of 2.6 and 3.4 Wm-1 K-1, respectively, for each epoxy matrix. This improvement is attributed to the formation of a three-dimensional heat flow path formed through intercalation of the nanotubes between the BNNS. The thermal conductivity of the epoxy 1 and 2 nanocomposites improved by 940 and 1500%, respectively, making them suitable as thermal interface materials in electronic applications requiring electrical resistivity.

Carbon Fiber/Phenolic Composites with High Thermal Conductivity Reinforced by a Three-Dimensional Carbon Fiber Felt Network Structure

The formation of highly thermally conductive composites with a three-dimensional (3D) oriented structure has become an important means to solve the heat dissipation problem of electronic components. In this paper, a carbon fiber (CF) felt with a 3D network structure was constructed through the airflow netting forming technology and needle punching. The carbon fiber/phenolic composites were then fabricated by CF felt and phenolic resin through vacuum impregnation and compression molding. The effects of CF felt content and porosity on the thermal conductivity of carbon fiber/phenolic composites were investigated. The enhancement of carbon skeleton content promotes the conduction of heat inside the composites, and the decrease of porosity also significantly improves the thermal conductivity of the composites. The results indicate that the composites exhibit a maximum in-plane thermal conductivity of 1.3 W/mK, which is about 650% that of pure phenolic resin, showing that the construction of 3D thermal network structure is conducive to the reinforcement of thermal conductivity of composites. The method can provide a certain theoretical basis for constructing a thermally conductive composite with a three-dimensional structure.

Epoxy Composites with High Thermal Conductivity by Constructing Three-Dimensional Carbon Fiber/Carbon/Nickel Networks Using an Electroplating Method

Heat dissipation problem is the primary factor restricting the service life of an electronic component. The thermal conductivity of materials has become a bottleneck that hinders the development of the electronic information industry (such as light-emitting diodes, 5G mobile phones). Therefore, the research on improving the thermal conductivity of materials has a very important theoretical value and a practical application value. Whether the thermally conductive filler in polymer composites can form a highly thermal conductive pathway is a key issue at this stage. The carbon fiber/carbon felt (CF/C felt) prepared in the study has a three-dimensional continuous network structure. The nickel-coated carbon fiber/carbon felt (CF/C/Ni felt) was fabricated by an electroplating deposition method. Three-dimensional CF/C/Ni/epoxy composites were manufactured by vacuum-assisted liquid-phase impregnation. By forming connection points between the adjacent carbon fibers, the thermal conduction path inside the felt can be improved so as to improve the thermal conductivity of the CF/C/Ni/epoxy composite. The thermal conductivity of the CF/C/Ni/epoxy composite (in-plane K∥) is up to 2.13 W/(m K) with 14.0 wt % CF/C and 3.70 wt % Ni particles (60 min electroplating deposition). This paper provides a theoretical basis for the development of high thermal conductivity and high-performance composite materials urgently needed in industrial production and high-tech fields.

Advances in Liquid Crystalline Epoxy Resins for High Thermal Conductivity

Epoxy resin (EP) is one of the most famous thermoset materials. In general, because EP has a three-dimensional random network, it possesses thermal properties similar to those of a typical heat insulator. Recently, there has been substantial interest in controlling the network structure of EP to create new functionalities. Indeed, the modified EP, represented as liquid crystalline epoxy (LCE), is considered promising for producing novel functionalities, which cannot be obtained from conventional EPs, by replacing the random network structure with an oriented one. In this paper, we review the current progress in the field of LCEs and their application to highly thermally conductive composite materials.

Inorganic-Organic Hybrid Janus Fillers for Improving the Thermal Conductivity of Polymer Composites

Janus fillers represent a combination of inorganic thermally conductive silver nanoparticles and organic polystyrene brushes on one entity but different sides. They are of practical importance for polymer composites with high thermal conductivity because of the improved dispersion and reduced interfacial heat resistance. Moreover, benefiting from the sheetlike structure and single-side deposition of inorganic particles, Janus fillers tend to align such that the heat pathway is constructed in the composite films, when fabricated by layer-by-layer doctor blading. As a result, the in-plane thermal conductivity of the polymer composite is as high as 4.57 W m^-1 K^-1, with only 10 vol % Janus filler loading.

Mussel-Inspired and Magnetic Co-functionalization of Hexagonal Boron Nitride in Poly(vinylidene fluoride) Composites Toward Enhanced Thermal and Mechanical Performance for Heat Exchangers

Thermal-conductive polymer composites have developed to be a hotspot in academic and industrial fields recently. Both efficient heat transport and superior mechanical properties are of critical significance for high-performance thermal-conductive devices. In this paper, magnetic hexagonal boron nitride (mhBN) with excellent interfacial compatibility is successfully synthesized by dopamine and magnetic co-functionalization, and mhBN-poly(vinylidene fluoride) (mhBN-PVDF) composites with a combination of high thermal conductivity and outstanding mechanical property are achieved due to the integration of excellent interfacial interaction and aligned filler architecture into one material's system. The thermal conductivity increases from 0.35 W/(m K) for the 20 wt % pure BN-PVDF to 0.82 W/(m K) after the dopamine modification and further to 1.43 W/(m K) after alignment. The effective medium approximation model demonstrates that the optimization of mhBN orientation and decrease of thermal resistance are two major factors for the enhancement of thermal conductivity. Moreover, the mhBN-PVDF composites also exhibit excellent tensile strength (168.5 MPa at 15 wt % content) and impact strength (20-30 kJ/m²). The significantly enhanced thermal and mechanical properties result in the excellent heat exchange ability and durability in the heat exchange test, which is important for potential application in the heat exchange industry.

Effective Assembly of Nano-Ceramic Materials for High and Anisotropic Thermal Conductivity in a Polymer Composite

Recently, anisotropic heat dissipation and its management have drawn attention as a promising technique for highly integrated electrical devices. Among many potentially challenging materials such as carbon nanotube, graphene, metal particles, and inorganic ceramics commonly used for high thermally conductive fillers in a composite form, nanoscale ceramic fillers are considered ideal candidates due to their thermal conductivity, electrical insulation, and low thermal expansion coefficient. However, enhancing the thermal conductivity of a randomly dispersed ceramic-polymer composite is limited by its discontinuous filler contact and thermal expansion coefficient mismatch. Thus, recent research has focused on how to assemble and generate highly networked filler contacts to make effective pathways for heat flow, with minimized concentration of the filler in the composite. In this review, we will introduce several essential strategies to assemble fillers with a two- or three-dimensional networked composite for highly enhanced anisotropic heat dissipation. Moreover, this review elucidates filler alignment effects compared to randomly dispersed ceramic composites.