Anisotropic Electromagnetic Shielding Performance of Polymer‐Based Composites Controlled by Aligned Graphene Nanoplates

ABSTRACT To control the orientation of graphene nanoplates (GNPs) in a polymer matrix and obtain polymer‐based composites with anisotropic electromagnetic shielding performance, polyurethane‐based composite films filled with GNPs and carbonyl iron powder (CIP) were fabricated using solution mixing and the solvent evaporation method. They were then thermally pressed and mechanically cut to form composite sheet plates. The as‐prepared composite films' and sheet plates' microstructures, electrical conductivities, magnetic permeabilities, and electromagnetic interference (EMI) shielding properties were characterized. The GNPs were oriented to form laminated structures in the films, and their orientation angles in the sheet plates were controlled by changing the layer angles during cutting. As the layer angle increased, the EMI shielding effectiveness (SE), including reflection and absorption, of the composite sheet plates decreased gradually, and CIP addition improved the absorption SE to varying degrees in different layer angles. The difference in the SE among various layer angles was attributed to different surface impedance matching and internal transmission channels of electromagnetic waves, which related to the orientation of the stacked GNPs. Furthermore, the SEs of the sheet plates having different layer angles were influenced by test angles to different degrees. In particular, the difference in total SE under various test angles reaching 36.2 dB when the layer angle was 90°. Owing to the anisotropic EMI SEs of the composite sheet plates, electromagnetic shielding properties were effectively controlled by the internal GNPs' state, which may be useful in the development of polymer‐based electromagnetic shielding composites with absorption‐dominated or controllable shielding performance.