Reusing Face Covering Masks: Probing the Impact of Heat Treatment

Abstract

The COVID-19 pandemic resulted in imminent shortages of personal protective equipment such as face masks. To address the shortage, new sterilization or decontamination procedures for masks are quickly being developed and employed. Dry heat and steam sterilization processes are easily scalable and allow treatment of large sample sizes, thus potentially presenting fast and efficient decontamination routes, which could significantly ease the rapidly increasing need for protective masks globally during a pandemic like COVID-19. In this study, a suite of structural and chemical characterization techniques, including scanning electron microscopy (SEM), contact angle, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman were utilized to probe the heat treatment impact on commercially available 3M 8210 N95 Particulate Respirator and VWR Advanced Protection surgical mask. Unique to this study is the use of the synchrotron-based In situ and Operando Soft X-ray Spectroscopy (IOS) beamline (23-ID-2) housed at the National Synchrotron Light Source II at Brookhaven National Laboratory for near-edge X-ray absorption spectroscopy (NEXAFS).

Figure 1

SEM images of individual layers in pristine, dry heat, and steam-treated N95 respirators (A) and VWR surgical masks (B).

Figure 2

Contact angle as a function of time for the 1st layer (A), heat-treated 1st layer (B), steam-treated 1st layer (C), 2nd layer (D), heat-treated 2nd layer (E), steam-treated 2nd layer (F), 3rd layer (G), heat-treated 3rd layer (H), and steam-treated 3rd layer (I) of 3M Particulate Respirator 8210 N95.

Figure 3

Contact angle and volume change as a function of time for the 1st layer (A), heat-treated 1st layer (B), steam-treated 1st layer (C), 2nd layer (D), heat-treated 2nd layer (E), steam-treated 2nd layer (F), 3rd layer (G), heat-treated 3rd layer (H), and steam-treated 3rd layer (I) of VWR Advanced Protection surgical mask.

Figure 4

XRD spectra of four layers in N95 respirators (A–D) and three layers in VWR surgical masks (E–G) before and after dry heat and steam heat treatments.

Figure 5

Raman spectra of four layers in N95 respirators (A–D) and three layers in VWR surgical masks (E–G) before and after dry heat and steam heat treatments.

Figure 6

C 1s XPS spectra of pristine, dry-heat-treated, and steam-treated N95 respirators.

Figure 7

C 1s XPS spectra of pristine, dry-heat-treated, and steam-treated VWR surgical masks.

Figure 8

C K-edge NEXAFS spectra of N95 layer 1–4 collected in PFY (A–D) and TEY (E–H) modes, respectively, where all spectra were normalized by setting the flat low energy region (∼280 eV) to zero and the peak maxima to one.

Figure 9

C K-edge NEXAFS spectra of VWR surgical mask layer 1–3 collected in PFY (A–C) and TEY (D–F) modes, respectively, where all spectra were normalized by setting the flat low energy region (∼280 eV) to zero and the peak maxima to one.