Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Engineering Science

Program

Mechanical and Materials Engineering

Supervisor

Straatman, Anthony G.

2nd Supervisor

Ogden, Kelly

Co-Supervisor

Abstract

This thesis documents the characterization of flexible polyurethane foam (FPF) to be used as a personal protective equipment material. Polyurethane samples were tested experimentally to calculate the physical properties which were later re-created using a numerical model. A discrete element modeling software was used to generate the geometry to mimic the physical properties of FPF. The pore level numerical model was used to calculate the possible rate of particle penetration for a range (0.2 -200) µm of particle sizes. A parametric study was done using the polyurethane foam parameters to understand the breathing dynamics under steady conditions. The possible particle penetration rate of a facile mask made of flexible polyurethane foam was detailed for different breathing conditions. The results show that a non-medical polyurethane foam mask can drastically reduce the risk of particle penetration for particles larger than 10µm. The process exemplifies a realistic study of facial masks to understand the dynamics and efficiency inside the interested material for any specific particle size and condition. A process to estimate the overall effectiveness of FPF mask when exposed to a cloud of different size particles is also demonstrated. The results indicate that a heavier breathing cycle will create a higher-pressure variation inside the mask surface in a few specific spots through which particles are most likely to penetrate. On the contrary, a normal breathing will create a moderately uniform pressure distribution inside the face mask which will draw in fewer particles when compared to the former cycle.

Summary for Lay Audience

Flexible polyurethane foam is an open cell foam that has recently been using as a personal protective equipment material. A type of flexible polyurethane foam specially designed to be used as a non-medical facial mask manufactured by FXI has been tested for its effectiveness in this study. To understand the physical properties of the foam and how fluid flow influences the foam sample, a set of experiments were conducted for a range of flow rates. To extensively study the FPF foam sample, a numerical model was required. The experimental results were than used to calibrate a numerical representative element volume (REV) that was developed in a way to replicate the physical foam samples. The pore level numerical model was used to understand the flow behavior inside the pores and an estimation of permeability and loss coefficient was done. A parametric study was introduced to understand the capability of FPF mask material in practical situations. A human face anatomy with a simple spherical mask covering was used as the numerical model under two different breathing conditions. The results from this parametric study were used to further understand the influence of particle penetration on a FPF mask. A total of 8 different particle sizes (0.2, 0.3, 0.5,0.7, 1,2,10,200) µm that present in atmospheric air was introduced in the air flow to investigate the filtration effectiveness of FPF. Filtration efficiency was estimated for each particle size on a pore level study using a possible range of velocities found during two different breathing cycle. The results show that a heavier breathing cycle generates more pressure inside the mask surface. The particle filtration test results conclude that the efficiency rate increases with velocity. However, there is a fluctuation of 3-5% in filtration efficiency for low velocities in the range (0.01-0.05) m/s. The filtration efficiency results can be used to precisely estimate an overall effectiveness of a mask for different velocities when exposed to a cloud of particles containing any range of particles sizes. The process and methodology used in this study can be adapted to be used for any material and shape of mask or personal protective equipment. This research investigates the function and effectiveness of porous material (Flexible polyurethane foam) through experiments, pore level numerical study with a parametric analysis to understand a real time situation.

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