THE SYNERGY OF MEDIA STRUCTURE AND CHARGE DISTRIBUTION IN A COMMERCIAL HVAC FILTRATION MEDIA

摘要

The synergy of web structure and charge distribution in electret filtration media is critical to the performance characteristics of the finished filter. We have conducted numerous field studies aimed at elucidating the functionality of electret charged continuous filament meltspun media in HVAC applications that included exposure to indoor and outdoor air, high and low humidity, and prolonged storage following manufacture. Each field study focuses on a particular aspect of filter media performance of concern to a potential enduser. The direct imaging of charge domains was accomplished through the use of a scanning electron microscope operated at very low primary beam voltage. The application of low energy electron imaging to filtration media has provided key insight into the distribution of charge in continuous filament meltspun filtration media. The images reveal a highly inhomogeneous distribution of charge within the filter web structure. An empirical model has been developed which describes the distribution of charge in electret filtration media as layers of alternating negative and positive charge domains. Electron microscopy imaging of electret charged filtration media are consistent with the model, as are observed surface potentials and net charges. The synergy of web structure and charge distribution has been demonstrated as key to the performance characteristics of electret HVAC media.