Charge characteristics of co-electrospun nanofiber membranes and their application in high-humidity environment

Abstract

Enhancing the charge density and charge stability is an important approach to improve the filtration performance of electrospun nanofiber air filters. In the present study, the polymers with different electron transport capabilities were co-electrospun in pairs to prepare charge-enhanced nanofiber membranes. The results showed that the average surface potential of the interfacial regions of polyamide 6 (PA6) and polyvinyl chloride (PVC) nanofibers was 165 mV, which was substantially higher than the non-intersection area of nanofibers. The charges induced by the contact-induced electrification between nanofibers accumulated in the intersection area of the hybrid nanofibers, which contributed to the high surface potential of the nanofiber membranes. Moreover, the co-electrospinning of polymers allowed the positively charged PA 6 nanofibers and negatively charged PVC nanofibers to coexist in the nanofiber membranes. Benefiting from these charge characteristics, the co-electrospun PA 6/PVC nanofiber membranes exhibited an average filtration efficiency of 99.73 % for 50–500 nm particles at the face velocity of 5.3 cm/s, and the pressure drop was 130 Pa. A hydrophilic fiber layer was employed to mitigate the influence of humidity on the charge decay and pressure drop growth of thenanofiber membrane. The growth rate of pressure drop of the protected nanofiber membrane was as low as 0.95 Pa/min under the challenge of water droplets. In contrast, the growth rate of pressure drop for common membrane based filters was in the range of 5–120 Pa/min. Additionally, the color of the hydrophilic layer changed corresponding to the water content in the air filters, which could serve as an indicator for the filter service life visible to naked eyes. This study provides a new approach for charging nanofiber membranes and improving their filtration performance stability in practical applications.