Improvement of thermal conductivities and simulation model for glass fabrics reinforced epoxy laminated composites via introducing hetero-structured BNN-30@BNNS fillers

Abstract

Hetero-structured thermally conductive spherical boron nitride and boron nitride nanosheets (BNN-30@BNNS) fillers were prepared via electrostatic self-assembly method. And the corresponding thermally conductive & electrically insulating BNN-30@BNNS/Si-GFs/E-44 laminated composites were then fabricated via hot compression. BNN-30@BNNS-III (fBNN-30/fBNNS, 1/2, wt/wt) fillers presented the optimal synergistic improvement effects on the thermal conductivities of epoxy composites. When the mass fraction of BNN-30@BNNS-III was 15 wt%, λ value of the BNN-30@BNNS-III/E-44 composites was up to 0.61 W m−1K−1, increased by 2.8 times compared with pure E-44 (λ = 0.22 W m−1K−1), also higher than that of the 15 wt% BNN-30/E-44 (0.56 W m−1K−1), 15 wt% BNNS/E-44 (0.42 W m−1K−1), and 15 wt% (BNN-30/BNNS)/E-44 (direct blending BNN-30/BNNS hybrid fillers, 1/2, wt/wt, 0.49 W m−1K−1) composites. The λ in-plane (λ//) and λ cross-plane (λ┴) of 15 wt% BNN-30@BNNS-III/Si-GFs/E-44 laminated composites significantly reached 2.75 W m−1K−1 and 1.32 W m−1K−1, 186.5 % and 187.0 % higher than those of Si-GFs/E-44 laminated composites (λ// = 0.96 W m−1K−1 and λ┴ = 0.46 W m−1K−1). Established models can well simulate heat transfer efficiency in the BNN-30@BNNS-III/Si-GFs/E-44 laminated composites. Under the condition of point heat source, the introduction of BNN-30@BNNS-III fillers were conducive to accelerating heat flow transfer. BNN-30@BNNS-III/Si-GFs/E-44 laminated composites also demonstrated outstanding electrical insulating properties (cross-plane withstanding voltage, breakdown strength, surface & volume resistivity of 51.3 kV, 23.8 kV mm−1, 3.7 × 1014 Ω & 3.4 × 1014 Ω·cm, favorable mechanical properties (flexural strength of 401.0 MPa and ILSS of 22.3 MPa), excellent dielectric properties (ε of 4.92 and tanδ of 0.008) and terrific thermal properties (Tg of 167.3 °C and THRI of 199.2 °C).