Multimodal Analysis of Surface Properties and Charge Dynamics in Teflon-FEP Electrets

This work investigates the electrostatic and dielectric behavior of Teflon-FEP electrets charged by corona discharge, revealing critical structure–property relationships that govern long-term charge stability. Surface charges ranging from 7.5 to 50 μC generated surface charge densities from 0.20 to 1.25 mC/m², corresponding to internal electric fields between 16.3 and 40.7 MV/m. Attenuated total reflection infrared spectroscopy (ATR-IR) revealed anisotropic attenuation of the C–F stretching modes at 1146 cm⁻¹ and 1209 cm⁻¹, indicating field-induced dipole alignment. Contact angle measurements showed a monotonic increase in the polar component of the surface energy from 2.8 to 12.1 mN/m, while the dispersive component remained nearly constant at ~20.4 mN/m. Atomic force microscopy (AFM) indicated a fivefold increase in root-mean-square roughness (from 5.6 to 27.3 nm), consistent with localized electrostriction and nanodomain formation. A logistic model (R² = 0.998) described the correlation between surface polarity and charge retention. Electrostatic force microscopy (EFM) further confirmed capacitive coupling between adjacent cylindrical domains, enhancing local electric-field gradients near the surface. Overall, these findings provide a robust framework for the tailored design of fluoropolymer electrets for high-performance acoustic sensors and dielectric systems.