Epoxy composite with high thermal conductivity by constructing 3D-oriented carbon fiber and BN network structure

Environment-friendly, high-performance cellulose nanofiber-vanillin epoxy nanocomposite with excellent mechanical, thermal insulation and UV shielding properties

With the increased demand for biobased epoxy thermosets as an alternative to petroleum-based materials in various fields, developing environment-friendly and high-performance natural fiber-biobased epoxy nanocomposites is crucial for industrial applications. Herein, an environment-friendly nanocomposite is reported by introducing cellulose nanofiber (CNF) in situ interaction with lignin-derived vanillin epoxy (VE) monomer and 4, 4´-diaminodiphenyl methane (DDM) hardener that serves as a multifunctional platform. The CNF-VE nanocomposite is fabricated by simply dispersing the CNF suspension to the VE and DDM hardener solution through the in-situ reaction, and its mechanical properties and thermal insulation behavior, wettability, chemical resistance, and optical properties are evaluated with the CNF weight percent variation. The well-dispersed CNF-VE nanocomposite exhibited high tensile strength (∼127.78 ± 3.99 MPa) and strain-at-break (∼16.49 ± 0.61 %), haziness (∼50 %) and UV-shielding properties. The in situ loading of CNF forms covalent crosslinking with the VE and favors improving the mechanical properties along with the homogeneous dispersion of CNF. The CNF-VE nanocomposite also shows lower thermal conductivity (0.26 Wm-1K-1) than glass. The environment-friendly and high-performance nanocomposite provides multiple platforms and can be used for building materials.

A study on the viscosity reduction mechanism of high-filled silicone potting adhesive by the formation of Al2O3 clusters

Heat dissipation has become a key problem for highly integrated and miniaturized electronic components. High thermal conductivity, good flowability and low coefficient of linear thermal expansion (CLTE) are indispensable performance parameters in the field of electronic potting composite materials. In this study, spherical alumina (Al₂O₃) was surface modified by γ-(2,3-epoxypropoxy) propyltrimethoxy silane (KH560) and γ-aminopropyltriethoxy silane (KH550) and labelled as Al₂O₃-epoxy and Al₂O₃–NH₂, respectively. Al₂O₃-epoxy and Al₂O₃–NH₂ powders were equally filled in vinyl silicone oil to prepare a high Al₂O₃ loading (89 wt%) precursor of silicone potting adhesive. The viscosity of the precursor rapidly decreased with increasing reaction time of Al₂O₃-epoxy and Al₂O₃–NH₂ at 140 °C. The viscosity reduction mechanism may be due to the formation of some Al₂O₃ clusters by the reaction of Al₂O₃-epoxy with Al₂O₃–NH₂, which results in some vinyl silicone oil segments being held in the channel of particles through capillary phenomenon, leading to the friction among Al₂O₃ clusters decreasing considerably. Laser particle size analysis and scanning electron microscopy (SEM) results confirmed the existence of Al₂O₃ clusters. Energy dispersive spectroscopy (EDS) and dynamic viscoelasticity experiments revealed that some segments of vinyl silicone oils were held by Al₂O₃ clusters. When Al₂O₃-epoxy and Al₂O₃–NH₂ reacted for 4 h, the thermal conductivity, CLTE and volume electrical resistivity of the silicone potting adhesive reached 2.73 W m⁻¹ k⁻¹, 75.8 ppm/°C and 4.6 × 10¹³ Ω cm, respectively. A new strategy for preparing electronic potting materials with high thermal conductivity, good flowability and low CLTE is presented.

Surface-modified Al₂O₃-epoxy reacts with Al₂O₃–NH₂ to form clusters that reduce the viscosity of electronic potting composites.