Self-Induced Localized Electric-Field-Enhanced Electrostatic Electron Emission in Polypropylene Surface-Based Roll-to-Roll Manufacturing

The roll-to-roll (RtR) Manufacturing can produce a large amount of electrostatic charges. In terms of industrial safety, a large amount of energy can be released via electrostatic discharge (ESD) that can cause severe shocks, which can be a risk to automated machines, operators, and merchandise. In this study, the ESD associated with the existing nonwoven Polypropylene (PP) manufacturing is minimized by designing and introducing a sharp-edge metal bar with a radius of curvature of 100 μm as a passive electrostatic charge dissipation system next to the PP winding stock roll. The coulombic force from the deposited charges on PP can induce a highly localized electric field (up to ~10⁶ V/cm) between the grounded metal edge and the nanoscale surface of the nonwoven PP fabric that reduces the potential barrier, causing electrostatic electron/ion emission or discharge from the insulating PP winding surface to the ambient air, especially along the metal edge. Further, the level of static charge associated with the RtR process is characterized using a noncontact electrostatic field (E-field) meter without contaminating and interrupting the production lines. Furthermore, the three-dimensional finite element method (FEM) is used to obtain an accurate electrostatic charge distribution based on the actual size of the winding stock roll, providing a comprehensive understanding of the self-induced E-field-assisted ESD during operation. The experiment and simulation indicate that 75% of the effective stored charge density is transferred through the air. Therefore, the induced field emission structure is cost effective for dissipating the electrostatic charges and minimizing the ESD hazards.