Mechanically robust polyimide/MXene/wood composite film for electromagnetic interference shielding and flame retardancy

Two-dimensional MXene materials have exhibited considerable promise for electromagnetic interference (EMI) shielding due to their excellent electrical conductivity. However, achieving excellent mechanical properties and high EMI shielding effectiveness (SE) simultaneously in such composite materials with the lowest content of MXene remains a continuing challenge. Herein, delignified wood (DW) aerogel with porous structure was obtained by the sodium chlorite method, and the ternary composite film of polyimide (PI)/MXene/DW was fabricated by sequential vacuum impregnation of MXene and polyamide acid solution, followed by hot pressing and thermal imidization. The introduction of PI significantly improves the mechanical properties of the composite film, exhibiting the tensile strength and modulus of 88.97 MPa and 2.93 GPa, respectively. The composite film exhibits the EMI SE of 15.2 dB in the X-band range with the MXene content of only 7 wt% and the thickness of 0.3 mm, corresponding to a high SE/ t of 50.7 dB/mm. Moreover, the composite film shows stable EMI shielding performance even after exposing in a variety of harsh environments and good flame retardancy properties. Therefore, the resulting composite film exhibits excellent EMI shielding and flame retardancy performance, which provides the potential applications in aerospace and related fields.