Bionic Engineering Strategy for Preparing Flexible Carbon Paper From Waste Polypropylene: Excellent Electromagnetic Shielding Performance and Multifunctional Integration

ABSTRACT Flexible paper‐based carbon materials are considered an advantageous choice for meeting the intelligent requirements of electromagnetic interference (EMI) shielding materials. Inspired by nacre structures, an economical and efficient multifunctional polypropylene‐based flexible carbon paper (PP‐CP) was prepared in this study using recycled polypropylene (rPP) and waste pre‐oxidized fibers as precursors. Based on the “heterogeneous swelling” effect of PP matrix during the liquid phase sulfonation process, a high‐strength flexible interpenetrating network structure was constructed from PP‐derived carbon and short‐cut carbon fibers (SCF). A synergistic 3D conductive network formed by SCF and PP‐derived microcracks resulted in a high electrical conductivity of 7735 S m ^{− 1} . The highest EMI shielding effectiveness (EMI SE) of 58.8 dB and thickness‐averaged specific SE (SSE/t) of 6642 dB·cm ² /g in the X‐band was exhibited by the PP‐CP, along with excellent joule heating, hydrophobicity, and breathability. The outstanding multifunctional integration features of PP‐CP meet the needs of next‐generation wearable electronic devices, while also paving a new path for the sustainable utilization of PP and carbon fiber resources.