Effect of pore structure regulation on the properties of 3D cellulose nanofiber electret filtration materials

The properties, electret property and purification performance, of electret filter materials are closely associated with its pore structure, but the effect mechanism of pore structure on its electret property has not been clarified. Herein, the pore structure of 3D electret fiber materials which were prepared by freeze-drying technology and corona polarization technology based on dialdehyde cellulose nanofibers (DAMCC) and ethyl cellulose nanofibers (EC) was regulated by changing the DAMCC/EC mass ratio, solvent system, pre-freezing temperature and fiber concentration to explore the influence of pore structure on its electret properties and purification performance. The results show that the charge trapping and storage properties can be altered by the regulation of pore structure, and the 3D fiber material, prepared under the conditions of DAMCC/EC nanofiber mass ratio of 1/2, TBA content of 10 %, pre-freezing temperature of −40 °C and fiber concentration of 1.5 w/v%, presents a cellular porous structure with a complete fiber mesh wall. This structure is not only beneficial to the migration of space charge to the interior of the fiber material, but also can effectively prevent the escape behavior of space charge inside the material by extending the tortuous pore channel length, thereby improving the initial and stable surface potentials from 0.72 kV and 0.02 kV to 1.19 kV and 0.47 kV respectively. Moreover, the purification time of 3D electret fiber materials can be reduced from 51 min to 13 min owe to the improvement of electret property and pore structure. These will provide guidance for the investigation of pore structure regulation to alter the properties of electret fiber material for air purification.