Document Type

Thesis

Date of Degree

Spring 2015

Degree Name

MS (Master of Science)

Degree In

Occupational and Environmental Health

First Advisor

Thomas M. Peters

Abstract

Porous polyurethane foam was evaluated as a potential replacement substrate for the eight nylon meshes currently being used in the diffusion stage of the Nanoparticle Respiratory Deposition (NRD) Sampler. A semi-empirical particle deposition model and preliminary tests were used to select the dimensions of foam substrate needed to match the collection of the NRD sampler at recommended sampling conditions. The foam substrate consisted of a cylinder nominally 25-mm diameter by 40 mm in depth, housed in a conductive plastic cassette cowl (internal diameter of 23 mm) compatible with the existing NRD sampler. Pristine foam was evaluated for metals content via acid-assisted microwave digestion and inductively coupled plasma-optical emissions spectroscopy (ICP-OES) chemical analysis. Foam collection efficiency was evaluated using salt (NaCl) and metal fume test aerosols in independent tests. Foam collection efficiency was compared to the nanoparticulate matter (NPM) criterion (established to reflect the total deposition in the human respiratory system for particles smaller than 300 nm) and theoretical modeling.

The collection efficiency of NaCl particles was similar to the NPM criterion (R2 = 0.98) and the model underestimated the experimental efficiency (R2 = 0.38). Increased collection efficiency of metal fume was observed for particles larger than 70 nm presumably due to increased interception effects of fractal shaped particles. The pressure drop across the pristine foam was 1/12th that of the nylon meshes. Foam and nylon meshes were loaded with metal fume particles to evaluate performance under simulated field conditions. Changes in collection efficiency and pressure drop were used as measures of performance. Foam had substantially lower changes in collection efficiency and pressure drop with ~ 19 mg metal fume loaded compared to the nylon meshes with ~ 3 mg metal fume loaded.

Public Abstract

Porous polyurethane foam was evaluated as a potential replacement for the eight nylon meshes currently used to collect nanoparticles in the Nanoparticle Respiratory Deposition (NRD) Sampler. A model for estimating particle collection in porous foam and preliminary tests were used to select the dimensions of foam needed to match specifications of the NRD. The foam was cut and placed in to a housing as to be compatible with the existing NRD sampler. Pristine foam was evaluated for background metals content via chemical analysis. The foam collection efficiency of nanoparticles was evaluated using salt and metal fume particles in independent tests. The foam collection efficiency was compared to collection efficiency criterion used to develop the NRD sampler and a model for estimating particle collection in porous foam.

The foam collection efficiency of salt particles was similar to NRD sampler design criterion but the model underestimated the experimental collection efficiency. The foam collection efficiency of metal fume was increased compared to the salt for larger nanoparticles presumably as a result of differences in particle shape that influenced particle collection. The pressure drop was lower across the pristine foam than the nylon meshes. Foam and nylon meshes were loaded with metal fume particles to evaluate performance under simulated field conditions. Changes in collection efficiency and pressure drop were used as measures of performance. Foam preformed substantially better than the nylon meshes when loaded with metal fume particles.

Keywords

publicabstract, Exposure, Foam, Industrial Hygiene, Nanoparticle, Personal Sampler, Sampling

Pages

ix, 87 pages

Bibliography

Includes bibliographical references (pages 84-87).

Copyright

Copyright 2015 Levi Walden Dyer Mines

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