Submicronic Filtering Media Based on Electrospun Recycled PET Nanofibers: Development, Characterization, and Method to Manufacture Surgical Masks

Abstract

The disposal of single-use personal protective equipment has brought a notable environmental impact in the context of the COVID-19 pandemic. During these last two years, part of the global research efforts has been focused on preventing contagion using nanotechnology. This work explores the production of filter materials with electrohydrodynamic techniques using recycled polyethylene terephthalate (PET). PET was chosen because it is one of the materials most commonly present in everyday waste (such as in food packaging, bags, or bottles), being the most frequently used thermoplastic polymer in the world. The influence of the electrospinning parameters on the filtering capacity of the resulting fabric was analyzed against both aerosolized submicron particles and microparticulated matter. Finally, we present a new scalable and straightforward method for manufacturing surgical masks by electrospinning and we validate their performance by simulating the standard conditions to which they are subjected to during use. The masks were successfully reprocessed to ensure that the proposed method is able to reduce the environmental impact of disposable face masks.

Keywords: COVID-19; PET; aerosol; electrospinning; face mask; fibers; filtration; nanotechnology.

Figure 1

Schematic representation of the PET-based face mask production.

Figure 2

Schematic representation of the equipment used for the particle penetration tests.

Figure 3

SEM micrographs and fiber size distribution histogram of electrospun fibers (n = 100) as a function of the polymer concentration (10, 15, 20 and 25 wt.%) in the solution electrospun at 5.0 mL/h flow rate.

Figure 4

(a) Morphology of the electrospun fibers as a function of the polymer concentration (10, 15, and 20 wt.% PET) and the solution output flow (0.5, 1.0, 2.5, and 5.0 mL/h) and (b) variation of the diameter of electrospun fibers (n = 100) depending on the output flow of the ejected solution.

Figure 5

Filtration efficiency using different parameters during electrospinning with a 25 wt.% PET solution. The noise to signal ratio of the curves increases from 0.6 µm because the equipment used is not designed to analyze coarse particles. Particle concentration >0.6 µm (∼1 × 10${}^5$ particles/cm${}^3$) is reduced compared to that of particles between 0.1 and 0.6 µm (∼2.5 × 10${}^5$–7 × 10${}^5$ particles/cm${}^3$).

Figure 6

(a) Filtering efficiency against submicronic particles (0.01–1.0 $\mathsf{\mu }$m) and pressure drop against different combinations of fiber diameters obtained by electrospinning solutions of 15 and 25 wt.% PET at different ratios and (b) solutions of 15–25 wt.% PET (3:1) at different fabric density.

Figure 7

Evaluation of the reproducibility of the electrospinning process at similar atmospheric conditions (RH of 36–42% and a T of 20.7–22.4 ${}^{°}$C) in triplicate.

Figure 8

Loss of filtering efficiency after 2 (a) and 4 (b) months of samples stored at room temperature against 0.01–10.0 $\mathsf{\mu }$m.

Figure 9

(a) PET-based surgical mask developed in this work (top) and a commercial surgical mask (bottom). (b) Macroscopic detail of the layers that make up the PET-based mask and (c) SEM views of the external layers and (d) the filter. (e) Macroscopic detail of the layers that make up the commercial surgical mask and (f) SEM views of the external layers and (g) the filter placed in the middle.

Figure 10

(a) Filtration efficiency of a PET-based surgical mask prepared in this work compared to a commercial surgical mask. The polydispersity range of particles used in the EN 14683:2019 surgical mask test is marked in red, and the range used in the EN 149:2001 standard, applicable to FFP2 (similar to KN95) and FFP3 (similar to KN99) masks, is marked in yellow. Labels for filtration efficiency at specific diameters (100, 300, 500, and 700 nm) can be seen on the graph. (b) The contact angle of the materials obtained compared to a commercial surgical mask.

Figure 11

(a) Filtration efficiency of a PET-based FFP2/KN95-type filter prepared in this work compared to a commercial filter mask. The polydispersity range of particles used in the EN 149:2001 standard, applicable to FFP2 (similar to KN95) and FFP3 (similar to KN99) masks, is marked in yellow. (b) SEM micrographs and fiber size distribution histogram of electrospun and commercial fibers (n = 100).

Figure 12

(a) Filtration efficiency of an initial PET fabric sample versus recycled (re-electrospun) PET fabric from an equivalent surgical mask and (b) SEM views of the PET fibers after reprocessing.

Figure 13

Schematic representation of the PET-based surgical mask concept.