Flexible microfibrillated cellulose/carbon nanotube multilayered composite films with electromagnetic interference shielding and thermal conductivity

Ultrathin, lightweight, and flexible materials with outstanding electromagnetic interference (EMI) and thermal conductivity (TC) performances simultaneously are urgently needed to effectively minimize the EMI issue and dissipate the accumulative heat. Herein, we prepared sustainable microfibrillated cellulose (MFC) reinforced carbon nanotubes (CNT) composite films (MFC/CNT) with an alternating multilayered structure by the facile vacuum filtration method. The effects of different structures on the mechanical, EMI shielding, and TC properties of composite films were comprehensively compared. All the mechanical, EMI shielding, and TC properties of the alternating multilayered MFC@CNT films were higher than those of homogeneous blend film. The tensile strength and fracture strain of the optimal film (M4C3, alternating structure with 4 layers of MFC and 3 layers of CNT) were 33.31 MPa and 5.86%, respectively. The corresponding EMI shielding efficiency (EMI SE) and specific EMI SE (SSE/t) values reached 26.67 dB and 9944 dB cm2/g at a thickness of 36 μm. Simultaneously, the optimal film also had a high anisotropic TC, the cross-plane and in-plane TC were 0.24 and 8.50 W/mK, respectively. This work provides guidance for fabricating high-performance CNT-based composite materials through structural design.