Textile & Clothing

Electret fibres for high-performance filter media – technical implementation

The project results supply a process that facilitates conversion of commercially available filter material into an electret. The latter provides a greater degree of protection from harmful exhaust air constituents produced by industrial processes. The new filter media allow a more efficient separation of micro-particles, prevent release of respirable particles and require substantially less energy.


One focus of work health and safety and environmental protection in the producing and heavy-duty industries is the removal of harmful dust and suspended substance particles from exhaust air. At present, purification media consist primarily of textile fabrics and non-wovens or electric filters. However, these have substantial drawbacks: they can release respirable particles, consume high amounts of energy, display high pressure loss due to the fine-mesh structure and require large package spaces due to the filter layers' surface area and thickness. Therefore, materials with special adsorptive properties based on the electret effect have been the object of recent research. This effect causes a permanent formation of electric charges in ferroelectric materials and plastics that achieves an electrostatic attraction otherwise produced only by electric filters. This project aimed to create fibres with electret properties to exploit this effect that will facilitate production of textiles and use in multivalent filter applications.

The collaborative project aimed to convert commercially available filter materials into electret filters through coating with a suitable substance and application of conventional corona technology.


  • Filter tests verify the effectiveness of the additionally obtained electrostatic forces.
  • The substance most suitable for inducing electret capacity is polyethylene hard paraffin wax.
  • Measurements remained reproducible over a period of up to one year.
  • In general, a positive corona results in a better separating performance in the micro-particle size range.
  • The electret effect is not destroyed by cleaning.
  • The electret filters generally retain their high separation capacity even after up to 20 cycles, while the original filters display substantially lower separation. Reactivation of the electret effect thus seems possible in principle.

More Project Informations

Project title:  Verbundprojekt: Integrierter Umweltschutz in der Textilindustrie - Plasmagestützte Herstellung von Elektretfasern für Hochleistungs-Filtermedien

Project number:  0339888, 0339890, 0339891

Project period:  2000 - 2004

Project region:  Germany (Hesse, Baden-Württemberg)

Project contact:

Herr Gorsler

This email address is being protected from spambots. You need JavaScript enabled to view it.

+49 (0)6641 / 970-51

+49 (0)6641 / 970-50

Herr Junker

+49 (0)7261 / 9283-42

+49 (0)7261 / 9283-99

Herr Dr. Stegmaier

+49 (0)711 / 9340-217

+49 (0)711 / 9340-297

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Source: German National Library of Science and Technology Hannover (TIB)