Tribocharging phenomena in sliding contacts between polymeric materials

Abstract

The electric double layer is known to affect thin film lubrication. Other researchers have shown that tribocharging affects the breaking torque in a metal shaft - oil-lip seal system and that an external electric field may be employed to control this phenomenon. One main issue in all these studies is the characterization of the charging state of the bodies in contact. This is quite a difficult challenge when the contact occurs between two insulating materials. The aim of the present work was to validate an experimental procedure appropriate for ensuring the reproducibility of the tribocharging conditions in sliding contacts between polymeric materials. The experiments were performed with samples of polystyrene and poly-vinyl-chloride. Surface potential measurements were done in order to evaluate the tribocharging effects. The experiments pointed out that the amount of charge accumulated on the sliding bodies depends on the external force applied to the contact and the number of tribocharging cycles (i.e., two back-and-forth relative motions). However, this charge is non-uniformly distributed on the surface of the samples. This means that it will be difficult to use tribocharging effect for controlling the charging state and hence the lubrication of the contact between two insulating bodies.