Materials analysis and image-based modelling of transmissibility and strain behaviour in approved face mask microstructures

Abstract

Comparisons are made between six different approved face masks concerning their particle transmissibility allied to mechanical properties. The latter involves material testing and stretch or strain behaviour under load. SEM and X-ray elemental analyses showed contrasting structures between random and ordered fibre orientations. These constitute the mask designs where transmissibility is to be minimised. Airflow velocity measurement enabled filtration to be measured between the different mask designs, from two to six layers of different fabrics in combination. SEM provided the fibre diameter and pore size of each mask layer, up to a maximum of six. Stretching each complete mask showed its elasticity and recovery behaviour on an energy basis. The energy conversion involved in mask straining involves areas enclosed within steady and cyclic load-extension plots. Thus, the work done in extending a mask and the energy recovered from its release identified a hysteresis associated with an irrecoverable permanent stretch to the mask fabric. Failure of individual layers, which occurred successively in extended stretch tests, appeared as a drop in a load-extension response. That change is associated with permanent damage to each mask and friction contact within the rearrangement of loose fibre weaves. Masks with the greatest number of layers reduced particle transmissibility. However, woven or ordered mask fabrics in two layers with different orientations provided comparable performance. Simulation of each mechanical response, velocity streamlining and fibre distribution within the mask layers are also presented.

Evaluating Droplet Survivability on Face Masks with X-ray Microtomography

“…Regarding the surface elemental composition represented in Figure C,F, the EDS technique detected that the most abundant element in all of the layers is carbon (C), denoted by red. This is associated with a hydrocarbon chain since polypropylene is the most common material for face mask manufacturing . From this analysis, it is also important to point out two other elements in the elemental mapping.…”

“…This is associated with a hydrocarbon chain since polypropylene is the most common material for face mask manufacturing. 50 From this analysis, it is also important to point out two other elements in the elemental mapping. For the surgical face mask's outer layer, there is the presence of the element titanium (Ti), in light blue (Figure 3C).…”

Design and Evaluation of Face Mask Filtration: Mechanisms, Formulas, and Fluid Dynamics Simulations

“…In our previous study [5], we analyzed the air velocity profile distribution based on the k-ε turbulence model for the six different face masks. In this study, we analyzed the air velocity profile distribution of these masks using the quadrant-based average velocity model (Equation ( 10)).…”

“…PPE is no longer mandatory, but its use is still encouraged in many countries around the world [3,4]. One of the parameters used to determine the performance of a face mask is its filtration efficiency [5]. Filtration efficiency is defined as the ability of a face mask to protect the wearer from the passage of airborne particles [6].…”

“…Approved masks can have up to six layers (FFP3) constructed in this manner, but normally fewer layers are employed. A range of masks with these properties were investigated [5,9]. This model has the advantage of a mathematical analysis of the average central air flow velocity in connection with filtration efficiency determination.…”