Robert N. Phalen

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Dr. Robert N. Phalen is an Associate Professor of Occupational Safety and Health with specializations in industrial hygiene or safety. Dr. Phalen has expertise in the comprehensive practice of industrial hygiene, with specific expertise in exposure assessment, indoor air quality, noise, personal protective clothing and equipment, and ergonomics.


Recent Submissions

Now showing 1 - 10 of 10
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    Tensile Properties and Integrity of Cleanroom and Low-modulus Disposable Nitrile Gloves: A Comparison of Two Dissimilar Glove Types
    (Annals of Occupational Hygiene, 2012) Phalen, Robert
    Background: The selection of disposable nitrile exam gloves is complicated by (i) the availability of several types or formulations, (ii) product variability, and (iii) an inability of common quality control tests to detect small holes in the fingers. Differences in polymer formulation (e.g. filler and plasticizer/oil content) and tensile properties are expected to account for much of the observed variability in performance. Objectives: This study evaluated the tensile properties and integrity (leak failure rates) of two glove choices assumed to contain different amounts of plasticizers/oils. The primary aims were to determine if the tensile properties and integrity differed and if associations existed among these factors. Additional physical and chemical properties were evaluated. Methods: Six clean room and five low-modulus products were evaluated using the American Society for Testing and Materials Method D412 and a modified water-leak test to detect holes capable of passing a virus or chemical agent. Results: Significant differences in the leak failure rates and tensile properties existed between the two glove types (P ≤ 0.05). The clean room gloves were about three times more likely to have leak failures (chi-square; P = 0.001). No correlation was observed between leak failures and tensile properties. Solvent extract, an indication of added plasticizer/oil, was not associated with leak failures. However, gloves with a maximum modulus <4 MPa or area density (AD) <11 g cm−2 were about four times less likely to leak. Conclusions: On average, the low-modulus gloves were a better choice for protection against aqueous chemical or biological penetration. The observed variability between glove products indicated that glove selection cannot rely solely on glove type or manufacturer labeling. Measures of modulus and AD may aid in the selection process, in contrast with common measures of tensile strength and elongation at break.
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    Chemical Resistance of disposable nitrile gloves exposed to simulated movement
    (Journal of Occupational and Environmental Hygiene, 2012) Phalen, Robert
    Large discrepancies between laboratory permeation testing and field exposures have been reported, with indications that hand movement could account for a portion of these differences. This study evaluated the influence of simulated movement on chemical permeation of 30 different disposable nitrile glove products. Products were investigated out-of-box and with exposure to simulated whole-glove movement. Permeation testing was conducted using ethanol as a surrogate test chemical. A previously designed pneumatic system was used to simulate hand movement. No movement and movement tests were matched-paired to control for environmental conditions, as were statistical analyses. Permeation data were collected for a 30-min exposure period or until a breakthrough time (BT) and steady-state permeation rate (SSPR) could be determined. A third parameter, area under the curve at 30 min (AUC-30), was used to estimate potential worker exposure. With movement, a significant decrease in BT (p ≤ 0.05), ranging from 6-33%, was observed for 28 products. The average decrease in BT was 18% (p ≤ 0.001). With movement, a significant increase in SSPR (p ≤ 0.05), ranging from 1-78%, was observed with 25 products. The average increase in SSPR was 18% (p ≤ 0.001). Significant increases in AUC-30 (p ≤ 0.05), ranging from 23-277%, were also observed for all products where it could be calculated. On average, there was a 58% increase (p ≤ 0.001). The overall effect of movement on permeation through disposable nitrile gloves was significant. Simulated movement significantly shortened the BT, increased the SSPR, and increased the cumulative 30-min exposure up to three times. Product variability also accounted for large differences, up to 40 times, in permeation and cumulative exposure. Glove selection must take these factors into account. It cannot be assumed that all products will perform in a similar manner.
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    Evaluation of coarse and fine particulate sources using a portable aerosol monitor in a desert community
    (Bulletin of Environmental Contamination and Toxicology, 2012) Phalen, Robert
    The purpose of this study was to use a portable aerosol monitor as a preliminary screening tool to identify local sources of coarse (PM10–2.5) and fine (PM2.5) particulate matter within the Coachella Valley, a low-elevation desert community. The portable aerosol monitor proved to be useful in identifying particle sources unique to the region, namely, sand dunes with sparse ground cover (vegetation), a river wash, and diesel truck and freight train traffic. The general limitations relate to discrepancies in the fraction of PM10–2.5 when compared to regional air quality data and a lack of accurate mass-based data.
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    Changes in chemical permeation of disposable latex, nitrile and vinyl gloves exposed to simulated movement
    (Journal of Occupational and Environmental Hygiene, 2014) Phalen, Robert
    Glove movement can affect chemical permeation of organic compounds through polymer glove products. However, conflicting reports make it difficult to compare the effects of movement on chemical permeation through commonly available glove types. The aim of this study was to evaluate the effect of movement on chemical permeation of an organic solvent through disposable latex, nitrile, and vinyl gloves. Simulated whole-glove permeation testing was conducted using ethyl alcohol and a previously designed permeation test system. With exposure to movement, a significant decrease (p ≤ 0.001) in breakthrough time (BT) was observed for the latex (-23%) and nitrile gloves (-31%). With exposure to movement, only the nitrile glove exhibited a significant increase (p ≤ 0.001) in steady-state permeation rate (+47%) and cumulative permeation at 30 min (+111%). Even though the nitrile glove provided optimum chemical resistance against ethyl alcohol, it was most affected by movement. With exposure to movement, the latex glove was an equivalent option for overall worker protection, because it was less affected by movement and the permeation rate was lower than that of the nitrile glove. In contrast, the vinyl glove was the least affected by movement, but did not provide adequate chemical resistance to ethyl alcohol in comparison with the nitrile and latex gloves. Glove selection should take movement and polymer type into account. Some glove polymer types are less affected by movement, most notably the latex glove in this test. With nitrile gloves, at least a factor of three should be used when attempting to assign a protection factor when repetitive hand motions are anticipated. Ultimately, the latex gloves outperformed nitrile and vinyl in these tests, which evaluated the effect of movement on chemical permeation. Future research should aim to resolve some of the observed discrepancies in test results with latex and vinyl gloves.
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    Study of the Mechanism on the Permeation of Ethanol in Nitrile Rubber Gloves Using Positron Annihilation Lifetime Spectroscopy
    (Journal of Applied Polymer Science, 2015) Phalen, Robert
    Positron annihilation lifetime spectroscopy (PALS) was applied to study the mechanism of ethanol diffusion through commercial nitrile rubber gloves. Even though the untreated raw samples were very different in their colors and area densities (g/cm2), the correlation between the ethanol diffusion coefficient from permeation test and the free volume from PALS measurement is well consistent with the Vrentas‐Duda model. Via combining the PALS technique and the Vrentas‐Duda theory, it is revealed that (a) the diffusion coefficient is correlated to the number of free volume holes rather than the average size of holes, (b) the diffusion process is not regulated by the size of ethanol molecule but by the size of critical volume for polymer segments to migrate, (c) nitrile group does not present in the free volume hole where the diffusion of ethanol molecule takes place, but is embedded in polymer matrix, and therefore, does not directly interact with ethanol molecule, and (d) nitrile group affects the average size, but not the number of free volume holes. The experiment demonstrates that the PALS technique, being mainly used in pure academic researches, might have application in the glove industry due to its ability in measuring terminal free volume quantities, which are directly related to the permeation of small organic molecules through protective gloves.
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    Polymer Properties Associated with Chemical Permeation Performance of Disposable Nitrile Rubber Gloves
    (Journal of Applied Polymer Science, 2015) Phalen, Robert
    Unlike other chemical protective clothing and devices, disposable gloves are not reliably certified to exceed chemical permeation performance standards. In light of generalized chemical compatibility charts, significant variability in performance exists between similar products on the market. This study evaluates whether nitrile rubber composition and uniformity are better associated with the observed product variability in chemical resistance than the available mechanical testing (e.g., tensile strength) done on these products. The independent variables evaluated include two physical, three mechanical, and four compositional parameters. Based on correlation and multiple regression analyses, the factors associated with variation in permeation of ethanol are area density, acrylonitrile content, carboxylation of the base polymer, the amount of extractable oils and oily plasticizers, and polymer uniformity. Increases in area density, acrylonitrile content, and carboxylation improve chemical resistance. Decreases in extractable oils and polymer variability (uniformity) also improve chemical resistance. On average, these combined factors accounted for about 53–67% of the observed variability in permeation, which were moderate but not strong associations. In contrast, tensile strength accounted for about 1% of the observed variability, a negligible effect. These results support the notion that standardized tests and certification criteria need to address polymer composition and uniformity to reduce gaps in performance. However, in light of the lack of strong correlations, further evaluation with tighter control over chemical composition is warranted.
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    Study of highly porous polymers for H2 fuel storage using positron annihilation lifetime spectroscopy
    (International Journal of Hydrogen Energy, 2015) Phalen, Robert
    Positron annihilation lifetime spectroscopy (PALS) was applied to study the porosity of four highly porous polymers: Amberlite XAD 4, Amberlite XAD 16, Haysep S and Hypersol-Macronet MN 200, all of which have been evaluated for H2 fuel storage. PALS revealed two types of pores, with average sizes around 2.0 Å and 6.0 Å. It was also determined that the smaller pores have a larger adsorption potential, while the larger pores constitute most of the fractional free volume. At low temperature (77 K), large pores trap most H2 molecules in the condensed gas state, rather than adsorb H2 molecules on their internal wall, as characterized by the Brunauer–Emmett–Teller (BET) method. In addition, it was found that 1) the fractional free volume (fv) of large pores, 2) the uniformity of large pores, and 3) the relative percentage of small pores are all key factors in storing H2 molecules at a low temperature. Ultimately, the PALS technique, one of the most powerful tools in characterizing micropores at the Å scale, can provide more informational (e.g. pore size, number, distribution) and accurate (e.g. fractional free volume rather than specific surface area) knowledge on the porosity of materials potentially used for H2 fuel storage in the future.
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    Revising the formulization of the Narayanaswamy equation using the Adam-Gibbs theory
    (Journal of Non-Crystalline Polymers, 2016) Phalen, Robert
    Hodge's formulization of the Tool-Narayanaswamy-Moynihan (TNM) equation from the Adam-Gibbs (AG) theory was re-evaluated. The non-linearity parameter (x) and the apparent activation energy (Δh*) of the TMN equation were re-derived. Compared with the original derivations, the revised values of x and Δh* were better correlated with experimental results. Of particular importance, the revised theoretical x correctly predicts the experimental trend of x for the cooling rate of polystyrene, whereas the original derivation predicted an opposite trend. Furthermore, the new derivation establishes a strong relationship between the fragility coefficient (m) and the x of a material. The relationship correlates well with the experimental values for a wide range of materials. Ultimately, the revised equations for x and Δh* more precisely reveal the theoretical foundation of the phenomenological TNM equation, as it relates to structural relaxation of polymeric materials.
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    Evaluating polymer degradation with complex mixtures using a simplified surface area method
    (Journal of Occupational and Environmental Hygiene, 2017) Phalen, Robert
    Chemical-resistant gloves, designed to protect workers from chemical hazards, are made from a variety of polymer materials such as plastic, rubber, and synthetic rubber. One material does not provide protection against all chemicals, thus proper polymer selection is critical. Standardized testing, such as chemical degradation tests, are used to aid in the selection process. The current methods of degradation ratings based on changes in weight or tensile properties can be expensive and data often do not exist for complex chemical mixtures. There are hundreds of thousands of chemical products on the market that do not have chemical resistance data for polymer selection. The method described in this study provides an inexpensive alternative to gravimetric analysis. This method uses surface area change to evaluate degradation of a polymer material. Degradation tests for 5 polymer types against 50 complex mixtures were conducted using both gravimetric and surface area methods. The percent change data were compared between the two methods. The resulting regression line was y = 0.48x + 0.019, in units of percent, and the Pearson correlation coefficient was r = 0.9537 (p ≤ 0.05), which indicated a strong correlation between percent weight change and percent surface area change. On average, the percent change for surface area was about half that of the weight change. Using this information, an equivalent rating system was developed for determining the chemical degradation of polymer gloves using surface area.
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    Introduction to Air Pollution Science: A Public Health Perspective
    (Jones and Bartlett and American Public Health Association Press, 2011-11-10) Phalen, Robert
    This unique textbook examines the basic health and environmental issues associated with air pollution including the relevant toxicology and epidemiology. It provides a foundation for the sampling and analysis of air pollutants as well as an understanding of international air quality regulations. Written for upper-level undergraduate and introductory graduate courses in air pollution, the book is also a valuable desk reference for practicing professionals who need to have a broad understanding of the topic.