Flexible regenerated cellulose composite films with sandwich structures for high-performance electromagnetic interference shielding

Electromagnetic radiation pollution has become increasingly serious in the electronic, industrial, civil, and military fields. Lightweight, flexible, and high-performance electromagnetic shielding films have recently become popular research topics. Herein, regenerated cellulose (RC) was used as the matrix, multi-walled carbon nanotube (MWCNTs) and Fe3O4 nanoparticles were used as fillers, the sandwich-structured composite films (SCFs) containing MWCNTs/RC film as the surface layer and Fe3O4/RC film as the interlayer were successfully prepared via immersion phase conversion and mechanical pressing methods. SCFs exhibited a conductivity of 2.0 S m−1 and an excellent electromagnetic interference shielding effectiveness of 25.6 dB, which were 147% and 32% higher than those of the monolayer composite films at the same filler contents, respectively. The shielding mechanism was mainly attributed to electromagnetic dual energy dissipation and a “reflection–absorption–reflection” effect of the sandwich structure on electromagnetic waves. In addition, the maximum tensile strength of SCFs reached 18.0 MPa, which was attributed to the addition of MWCNTs and the construction of the sandwich structure.