Improved electrical performance of BOPP films by acidic treatment at an elevated temperature

The low surface charge stability of Biaxially Oriented Polypropylene (BOPP) film has resulted in its inability to satisfy advanced electrical requirements. In this work, physico-chemical surface modifications of the films were made to verify the effect of these modifications on its electrical properties. The chemical treatment was performed on BOPP films on single side by orthophosphoric acid (H₃PO₄) with various concentrations at 110 °C by 4 h. The Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy and the Scanning Electron Microscopy (SEM) were utilized to identify the chemical bonding and surface morphology variations during the treatments, respectively. Electrical performance was evaluated by Dielectric Relaxation Spectroscopy (DRS) and Isothermal Surface-Potential Decay (ISPD). The results confirmed that the improved charge stability, lower surface energy, lower permittivity ε_r and dielectric loss tanδ with higher acid concentrations. Molecular Dynamics (MDs) simulation was conducted via 3D maps of total electron density (TED) and molecular electrostatic potential (MEP), HOMO-LUMO energy levels analysis and the Density of States (DOS) in order to clarify the mechanism behind. The results obtained from both investigation methods were highly identical in terms of the effect of (H₃PO₄) on the charge stability due to the formation of shallower electron traps as well as the influence of morphological differences resulting from surface treatment.