Charging mechanism of polymers under gaseous water molecule

Charge amount at low humidities is large compared to that at high humidities. However, its mechanism is still unclear. Here we propose a charging mechanism of contacting between polyethylene (PE) and polytetrafluoroethylene (PTFE) in vacuum or under gaseous water molecules, viz., isolated water molecules in the space, based on the charging mechanism using density functional theory (DFT) calculations. Nonetheless, net charge signs of PE(+) and PTFE(-) remained unaltered in vacuum and under gaseous water molecules, the concentration of net f-electron transfer was increased from -0.10375 in vacuum to -0.12125 in the presence of gaseous water molecules. This increase of net transferred f-electron is due to an increase of the average driving force from 0.03912 a.u. in vacuum to 0.04108 a.u. under gaseous water molecules. On the contrary, in the case of high humidity, a small amount of charge may be due to leak into thin water layer on the polymer surface. (c) 2024 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan All rights reserved.