Prevention of Electrostatic Charge Generation in Filtration of Low-Conductivity Oils by Surface Modification of Modern Filter Media

The electrostatic charging behavior of filter elements operating in various hydraulic and lubricating
fluids has been re-examined from the perspective of fundamental material properties of the two
materials participating in the event. In contrast to the previously proposed mechanisms that
focused predominantly on fluid and material conductivities, new evidence strongly suggests that
the relative placement of the substrates in the triboelectric series must be taken into account. The
positions occupied in the triboelectric series account for the donor/acceptor tendencies exhibited
by the materials when brought close together in close proximity ( 10 nm). Nevertheless, this
behavior is only an outward manifestation of the deeper underlying characteristics that include
material surface energies and, looking even deeper, the associated electron work functions of the
interacting materials. Herein we provide several examples of the enhanced understanding of the
electrostatic charging/discharging (ESC/ESD) phenomena as they occur in the course of filtration
of hydraulic and lubricating fluids through modern filter elements constructed of synthetic glass
fiber and polymer materials.