Enhancement in the Electrical Properties and Electromagnetic Interference Shielding Performance of Acrylonitrile–Butadiene–Styrene/Carbon Nanotubes Foams via the Introduction of Bimodal Cell Structures

The cell structures of conductive polymer‐based composite foams significantly influence their electrical properties and electromagnetic interference (EMI) shielding effectiveness (SE), necessitating a thorough understanding of how these properties improve with evolving cell structures. In this study, supercritical CO 2 foaming technique was manipulated to fabricate acrylonitrile–butadiene–styrene (ABS)/carbon nanotubes (CNTs) foams. The constant‐temperature mode was used to prepare unimodal foams (UF), while the bimodal foams (BF) were produced by varying‐temperature mode. The foaming properties, electrical conductivity, complex permittivity, and EMI SE of ABS/CNTs foams with various cell structures are methodically investigated at identical volume expansion ratio and CNTs content. The electrical conductivity of bimodal ABS/CNTs foam with CNTs content of 20% (BF‐C20) is 0.2191 S cm −1 , higher than that of unimodal ABS/CNTs foam with CNTs content of 20% (UF‐C20) (0.1765 S cm −1 ) owing to the introduction of bimodal cell structures. Complex permittivity results manifest that at 8.2 GHz, the ε ′ and ε ″ of BF‐C20 are 67.7 and 74.5, respectively, which are higher than 57.9 and 52.9 of UF‐C20. Among all ABS/CNTs foams, the total EMI SE of BF‐C20 attains the highest EMI shielding value, which reaches 30.2 dB. Furthermore, the absolute shielding effectiveness of BF‐C20 is 188.5 dB (g cm −2 ) −1 , which is 17.3% higher than that of UF‐C20.