Light‐Permeable Air Filter with Self‐Polarized Nylon‐11 Nanofibers for Enhanced Trapping of Particulate Matters

Abstract

Recently, there is a growing demand of high‐performance, lightweight, and light‐permeable air filters due to severe air pollution. Nanofiber air filters have been actively investigated to filter out ultrafine particulate matters (PMs) in air. Among various polymer nanofibers, Nylon‐6 nanofibers have been widely adopted to fabricate air filters owing to their mechanical strength and chemical stability. However, the filtering efficiency of the Nylon‐6 air filter is relatively low when it has high light transmittance. Thus, a relatively thick nanofiber layer is required to ensure the filtering efficiency, leading to a high pressure drop and low light transmittance. Herein, the fabrication and performance of an air filter made of ferroelectric Nylon‐11 nanofibers is introduced. The air filters fabricated with ferroelectric Nylon‐11 demonstrate much improved PM filtering efficiency due to their spontaneous polarization. Specifically, for inorganic PMs, a higher filtration efficiency of ≈70% is obtained for trapping PM2.5 using the filter with 80% light transmittance, which is ≈20% higher compared to that of the Nylon‐6 air filter with the same light transmittance. Particularly, the Nylon‐11 air filter exhibits higher quality factors for both organic and inorganic PMs owing to its high filtering efficiency and breathability. The approach introduced herein is a simple route for fabricating high‐performance air filters.

Stretchable and Compressible Si3N4 Nanofiber Sponge with Aligned Microstructure for Highly Efficient Particulate Matter Filtration under High‐Velocity Airflow

“…Additionally, we compared the filtration efficiency, airflow velocity, ratio of pressure drop to airflow velocity (υ/ΔP; the larger the value, the smaller the pressure drop under the same gas flow rate), QF, and working temperature with those of other light filtration materials, such as commercial glass fibers, reported electrospun or blow spinning fibers, and ceramic nanofiber-based filters. As presented in Figure 4k, compared to electrospun or blow spinning fiber filter materials, [10,12,13,16,[28][29][30][31][32][33][34][35] our Si 3 N 4 NFS has a higher working temperature owing to its ceramic nature. Compared to ceramic-based filters, [14,[17][18][19][20][21]36] our Si 3 N 4 NFS showed better tolerance toward high airflow velocity, sharing almost the same high efficiency but significantly lower pressure drop under the same airflow velocity.…”

“…[13] The other is a fibrous air filter, which exhibits a highly porous microstructure that is assembled by micrometer-sized fibers or nanofibers and captures PMs via a series of mechanisms such as physical interception, adhesion, and electrostatic interaction. [14][15][16] Compared with micrometer-sized fibrous air filters, nanofiber-based filters have higher PM trapping efficiency owing to their smaller pores and higher porosity. Nanofibrous air filters also have a low pressure drop because of the similar size of the nanofiber diameter and the average path of air molecules.…”

Global View and Trends in Electrospun Nanofiber Membranes for Particulate Matter Filtration: A Review

“…[ 44 ] Ferroelectric Nylon‐11 nanofibers demonstrated a filtration efficiency of ≈70% is obtained for PM 2.5 capture with 80% light transmittance. [ 48 ] An electrically activated surface covered with 2D nanonets achieves 99.998% efficiency for PM 0.3 maintaining low air resistance of 93 Pa and transmittance of 91% [ 54 ] and also, similar transparent electret nanofibers have been reported. [ 63,108 ] Free‐standing PU nanofiber/nets filters exhibit PM 1−0.5 filtration efficiency of >99.00%, PM 2.5−1 filtration efficiency of >99.73%, maintaining high light transmittance of ≈70%, and PM 0.3 filtration efficiency of >99.97% with ≈40%.…”

“…Their fabrication process is simpler and their efficiency relies only on physical mechanisms (related to the fiber diameter (FD), membrane porosity, thickness, and particle size) and the surface energy associated to the material chemistry, that is, based on interactions between the PM functional groups and the filter material, thereby, polymers with higher dipole moments are preferred [ 36,37 ] or interactions due to material electrical properties. Some materials reported by different authors in single polymer nanofibers are: polyacrylonitrile (PAN), [ 38–45 ] different polyamide (PA) types like PA‐56, PA‐6 and Nylon‐11, [ 46–48 ] polyvinyl alcohol (PVA), [ 39 ] poly(methyl methacrylate) (PMMA), [ 49 ] polyurethane (PU), [ 50 ] polyvinylidene fluoride (PVDF), [ 39,40,51–54 ] Polytetrafluoroethylene (PTFE), [ 13 ] cellulose acetate (CA), [ 55–58 ] meta‐aramid, [ 10 ] polylactic acid (PLA), [ 59 ] polycaprolactone (PCL), [ 60,61 ] polyetherimide (PEI), [ 62 ] polyimide (PI), [ 63 ] polyethylene terephthalate (PET). [ 8 ]…”

Ferroelectric PVDF nanofiber membrane for high-efficiency PM0.3 air filtration with low air flow resistance

“…The electrospinning method enables facile nanofiber (NF) membrane fabrication with an ultrathin diameter (10–1000 nm) under a high electric field [33] , [34] , [35] , which is considered to be an advanced physical filter that adopts the slip effect region of the air flow. Other strategies have been extensively implemented to increase the capture of fine dust, including chemical functionalization [36] and filter charging [37] . Among them is ferro/piezo-electricity, which employs a unique electroactive property with stable spontaneous polarization to efficiently trap microdust with a large built-in electric field ( Scheme 1 c ) and prevent the inhalation of PM.…”