Investigating the Structural, Thermal, Electric, Dielectric, and EMI Shielding Properties of Porous Thermoplastic Polyurethane Reinforced with Carbon Fiber/Magnetite Fillers

In this study, Fe₃O₄-chopped carbon fiber (CF) fillers with varying CF:Fe₃O₄ weight ratios (1:0.5, 1:0.75, and 1:1) were fabricated using the wet chemical reduction method. Different weight percentages (1, 3, 7 wt.%) of the CF/Fe₃O₄ fillers were used to fabricate lightweight, flexible, and porous thermoplastic polyurethane (p-TPU) composites for electromagnetic interference (EMI) shielding applications. Due to its poor electrical and magnetic properties, the TPU matrix alone exhibited negligible shielding effectiveness. The electromagnetic interference (EMI) performance of TPU composites is greatly affected by the amount of filler materials, the CF/Fe₃O₄ ratio, and the porous structure, which in turn influence the interfacial interactions between filler and p-TPU matrix. Effective electromagnetic attenuation is achieved by conductive CF network, interfacial polarization at CF/Fe₃O₄/TPU interfaces, and multiple internal reflections promoted by microstructural heterogeneity and porosity. A maximum EMI shielding effectiveness (SE_T) of 22.28 dB was achieved for a CF/Fe₃O₄/p-TPU composite with a filler load of 7 wt.%, a CF:Fe₃O₄ ratio of 1:1, and a porosity of 15%.