Effects of Volatile Compounds on Breakdown Field Strength Measurements of Polymers

This study investigates the effects of absorbed water and volatile compounds on measurements of the electrostatic breakdown field strength. Comparisons are made between sets of pristine samples, ones that underwent a thorough vacuum bake out, and ones subsequently exposed to humid conditions to determine how quickly the samples reverted to an unbaked state. Specifically, we compared signatures related to electrostatic breakdown (electrostatic breakdown field strength, frequency of pre-breakdown arcing, and flashover) and images of the arc damage sites. The work reports results for three prototypical polymeric dielectric materials: low density polyethylene (LDPE), polyether-etherketone (PEEK), and Nylon 66, listed in order of decreasing hydrophobicity. Electrostatic breakdown strength was seen to change linearly with effective exposure time; hydrophobic LDPE and intermediate PEEK increased, while more hydrophilic Nylon 66 decreased. Similar trends were observed for the number of pre-breakdown arcs (DC partial discharges) versus effective exposure time.