Effect of electrical field treatment on thermal conductivity and mechanical strength of carbon nanofiber/polymer composite sheets with high filler content.

Electrical field treatment (EFT) using alternating current was investigated for the possibility that it could enhance the out‐of‐plane effective thermal conductivity (TC) of carbon nanofiber (CNF)/polymer composite sheets with high concentrations of filler. Two types of polymers were used as the base: fluorinated polyimide (PI) and silicone rubber. For the CNF/fluorinated PI, the influence of frequency was clarified at 2 kV of amplitude voltage when using a CNF concentration up to 15.0 vol%. As a result, the effective TC was clearly increased by EFT, and the degree of the enhancement of effective TC was obviously greater at 0.01 Hz than at either 100 or 1 × 106 Hz. Moreover, the effective TCs of two types of CNF/silicone rubber were also enhanced by EFT with 2 kV and 0.01 Hz for concentrations of CNF up to 5.2 vol%, although there is a large difference in the preparation methods between CNF/fluorinated PI and CNF/silicone rubber. Furthermore, the tensile strength of the sheets prepared with EFT implied a change in the orientational structure of CNF inside the silicone rubber matrix, although the effect of EFT on the tensile strength was smaller compared with that on the effective TC. [ABSTRACT FROM AUTHOR]