Flexible Hierarchical Polyimide/Polypyrrole/Carbon Nanofiber Composite Films for Tunable Electromagnetic Interference Shielding

With the booming of telecommunication and microelectronics, it is essential to develop electromagnetic interference (EMI) shielding materials with low reflectivity characteristics to avoid the secondary pollution from electromagnetic waves (EMWs). Herein, we fabricated a series of hierarchical polypyrrole/carbon nanofiber (PPy/CF) composites with multilayer PPy films. The EMI shielding performance can be adjusted by attaching different layered PPy films. The EMI shielding efficiency (SE) of PPy/CF composite films can reach to 74.59 dB with an electrical conductivity of 3.02 x 10(-3) S/mm. Moreover, in order to make the composite film have excellent strength and flexibility, we specially designed an acetone-soluble polyimide (PI) resin to encapsulate PPy/CF. After packaging with PI, the composite films are imparted with high flexibility and mechanical properties with the tensile strength and modulus of 4.65 and 153.03 MPa, respectively. Moreover, the resultant PI/PPy/CF composite films also possess favorable Joule heating performance and sensing monitoring. The Joule heating temperature of PI/PPy/CF films reaches 131.0 C-degrees within 15 s when the applied voltage is 5 V. The fabricated composite films are promising for applications in the fields of aerospace, telecommunication, and microelectronic engineering and multifunctional wearable devices.