Surface Energy Modification of Filter Media to achieve optimal Performance Characteristics in select Applications

The surface modification of modern filter media is examined from the perspective
of the energetic properties and how they influence select filtration applications. In
contrast to the known mechanical filtration mechanisms, which are mainly applicable
to the solid-liquid separations, new findings strongly suggest that direct interaction
forces between the filter and the functional fluids must be taken into account in order
to achieve sufficient efficiencies. Separation processes of liquid phases such as liquidliquid
coalescence (LLC) or the treatment of process gases with liquid-gas coalescence
(LGC) require special properties of filter media with regard to the degree of interaction
with these phases. These include but are not limited to surface energy, wettability,
chemical resistance, etc. The focus falls increasingly on eliminating the undesired
interactions of modern filters with the fluid to be filtered. Filtration with modern
fine filter media can result in undesired additive removal (ADDREM), particularly of
those additives that are not fully dissolved in carrier fluid. Specifically this refers to
the removal of antifoamants from gear oils, which lead to serious consequential damage
of those systems. The interfacial interactions between the filter media and the
functional fluids are also responsible for other effects such as the highly undesirable
phenomenon of electrostatic charging/discharging (ESC/ESD) during the filtration of
low-conductivity oils. In this work, the effect of the surface energy modification, in
particular, is examined in greater detail. Ultimately, the surface energy of modern
filter media is characterized and modified in order to optimize their performance in
select applications. The work also presents some examples that illustrate the importance
of surface energy in highly challenging filtration applications.