In this article, the polyimide (PI) composite films with synergistically improving thermal conductivity were prepared by adding a few graphene nanoplatelets (GNP) and various hexagonal boron nitride (h-BN) contents into the PI matrix. The thermal conductivity of PI composite film with 1 wt% GNP and 30 wt% h-BN content was 1.21 W(m·k)− 1, which was higher than that of the PI composite film with 30 wt% h-BN content (0.45 W(m·k)− 1), the synergistic efficiency of GNP under various h-BN content (10 wt%, 20 wt%, and 30 wt%) were 1.70, 2.71, and 3.09, respectively. And it was found that the increased h-BN content can suppress the dielectric properties caused by GNP in the matrix. The dielectric permittivity and dielectric loss tangent of 1 wt% GNP/PI composite film were 10.69, 0.661 at 103 Hz, respectively, and that of the 30 wt% h-BN + GNP/PI composite film were 4.29 and 0.1367, respectively. Moreover, the mechanical properties of the PI composite film were suitable for practical applications. And the heat resistance index and the residual rate at 700°C of PI composite film increased to 326.8°C, 74.43%, respectively, and these of PI film were 292.6°C and 59.26%. Thus, it may provide a reference value for applying the filler hybridization/PI film in the electronic packaging materials.
In this study, a polyimide gel material with a high spatial network structure was synthesized. The pyrolysis process increased the material’s porous structure and specific surface area to improve the specific capacitance. The effects of pyrolysis temperature on morphology, structure, thermal, mechanical, and electrochemical properties were studied. The gel material is in the frozen state of the molecular chain from the frozen state to the moving state before 400°C. At the same time, pore structure formation with a weight loss rate of 11.9% in the decomposition state at 400°C–600°C, showing the breakage of the molecular chain and the decomposition of the polymer. With the increase of carbonized temperature, the pore structure becomes more compact while the pore size becomes smaller due to the reconstruction of the polymer structure. Meanwhile, due to the stable formation of carbon skeleton and the increase of carbon amount, the PI gel carbonized material’s thermal conductivity was improved to 1.458 [Formula: see text], which was 330% higher than that of pure PI gel (0.339 [Formula: see text]). Furthermore, the carbonized materials exhibit a specific capacitance of 66.17 [Formula: see text] and show good redox reversibility, apparent concentration polarization and good ion diffusion effect during charging and discharging, suggesting it is a promising electrode material for supercapacitors.
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