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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

ADVANCED MATERIALS AND FABRICATION METHODS FOR FLAME RETARDANT APPLICATIONS

Wojtal, Patrick January 2016 (has links)
Investigation of flame retardant materials (FRM) identified materials as effective substitutes for halogenated FRM. Many promising materials were tested such as hydrotalcite-type Al–Mg–Zr complex hydroxide, huntite, aluminum hydroxide, hydrotalcite, magnesium carbonate hydroxide pentahydrate, magnesium sulfate heptahydrate, magnesium phosphate hydrate, magnesium chloride hexahydrate, sodium metasilicate pentahydrate, XZO 2022 (Mg3Al) and halloysite. Electrophoretic deposition (EPD) manufacturing technique has been developed for the fabrication of coatings containing the most promising FRM candidates. Identifying charging and dispersion agents, such as poly(4-vinylpyridine-co-butyl methacrylate), humic acid, 2,2′- biquinoline-4,4′-dicarboxylic acid, quaternized hydroxyethylcellulose ethoxylate, 3- phosphonopropionic acid, 16-phosphonohexadecanoic acid, octadecylphosphonic acid, celestine blue, chitosan, to facilitate EPD was of great importance for successful deposition of composite FRM films. The films were investigated using scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, thermogravimetric and differential thermal analysis, as well as Fourier Transform Infrared and Ultraviolet-Visible spectroscopy. / Thesis / Master of Science (MSc) / Technology is expanding, as is our understanding of the environmental and health impacts of chemicals. New flame retardant materials (FRM) must be developed to help protect against fire hazards in increasingly complex products, but care must be taken to avoid implementing dangerous chemicals. This work identifies new FRM which can be efficient replacements for widely used, but toxic FRM. FRM can be applied as a coating cheaply, quickly, and evenly onto substrates of even a complex shape. Techniques and additive chemicals are suggested to create advanced FRM coatings
2

Distribution of Polybrominated Diphenyl Ethers Among Demographic Categories

Merilis, Giorvanni 07 July 2017 (has links)
Polybrominated Diphenyl Ethers (PBDEs) are flame retardants widely used within the United States in various products such as plastics, electronics, textiles and furniture. With an increase in production and usage, PBDEs have recently emerged as a contaminant of concern. Due to their chemical structure, PBDEs have the propensity to bioaccumulate in mammals. In fact, elevated PBDE concentrations have been recorded in human breast milk. Due to the potential widespread exposure to PBDEs, this study investigates human blood concentrations of PBDEs generated through the 2003-2004 National Health and Nutrition Examination Survey. Through the use of statistical modeling, a comparison of mean PBDE concentrations in ng/g lipid is conducted based on age, gender and ethnicity. From a sample of 2337 individuals, the average blood concentration of PBDEs was approximately 81 ng/g lipid. The average PBDE concentration of males was significantly higher than females, using a 95% confidence level. In addition, PBDEs detected in human blood ranged approximately from 0.05 to 3676 ng/g lipid, with the highest concentrations found in black males. Also, a logistic regression analysis is conducted to determine whether an increase in background PBDE concentrations is a risk factor for obesity. Furthermore, the analyses of PBDEs are repeated for phthalates and polychlorinated Biphenyls for comparison. Finally, the measured concentrations of PBDEs are also compared to health outcome data known to show potential risk.
3

Leaching Potential of Metals and Brominated Flame Retardants in Obsolete Notebook Computers

Barnes, Otho 08 August 2009 (has links)
Due to the increasing use of electronic components and the accelerated rate in which these components become obsolete, there has been a dramatic increase of discarded electronic waste (E-waste). E-waste includes obsolete electronic products such as computers, scanners, cellular phones, etc. These electronic components are manufactured using a variety of hazardous materials. As these components are discarded, the toxic and hazardous substances may become mobile and could impact human health and the environment. The toxic substances of concern contained in E-waste include heavy metals and brominated flame retardants (BFRs). This study attempts to identify the leaching potential of BFRs and metals.
4

Giftfria förskolor i Nordmalings kommun : En inventering av förskolor med åtgärdsförslag för att möjliggöra en minskning av barns negativa hälsoeffekter till följd av kemikalieexponering

Norman, Belinda January 2016 (has links)
Humans are exposed to chemicals every day in our indoor environment. Chemicals have contributed to increased prosperity but also caused negative health effects. Children are vulnerable to chemicals because of their development and they breathe and drink more in relation to their body weight. That is why it’s important to reduce chemical exposure in environment for children. Preschools have a central role when it comes to materials and products that may pose a risk for exposure. The municipality has an important role to achieve a nontoxic environment which is based on a Swedish environmental quality goal (Non-toxic environment). This study is a part of the prioritized local environmental work in the municipal of Nordmaling. An inventory has been done to find out what type of chemicals that may expose children to harmful effects in preschools of Nordmaling. Electronic as a toy, soft and smelling toys, plastic around food and drinks, foam play pads were common products found during the inventory. This materials containing phthalates, brominated flame retardants, perfluorinated compounds, bisphenol A, lead and cadmium that can expose children through leaching into the indoor environment. A guidance have been constructed to achieve a non-toxic environment based on the results from the inventory in a cost effective way. The conclusion of the report is clear, identified problem areas can quickly be accomplished with small measures and low costs. Increased awareness of harmful substances and good routines for purchases and cleaning can further reduce the exposure to chemicals in the preschools.
5

Indoor emissions and fate of flame retardants : A modelling approach

Liagkouridis, Ioannis January 2016 (has links)
A significant number of consumer goods and building materials act as emission sources of flame retardants (FRs) in the indoor environment. As a result, FRs have become ubiquitous indoors raising concerns about human exposure and possible health implications. Once released indoors, FRs can escape to the outdoors where they can persist, be transported over long distances and present a threat to the environment. Despite the increasing number of studies reporting the occurrence of FRs in the indoor environment, the understanding of i) how and to what extent these chemicals are released from indoor sources, and ii) their subsequent fate indoors remains limited. The overarching objective of this thesis was to improve this understanding by assessing the indoor emissions and fate of FRs using a combination of multimedia modelling strategies and experimental/empirical approaches. Paper I identifies a number of knowledge gaps and limitations regarding indoor emissions and fate of FRs and the available modelling approaches. These include a limited understanding of the key emission mechanisms for low volatility FRs, uncertainties regarding indoor air/surface partitioning, poor characterization of dust and film dynamics and a significant lack of knowledge regarding indoor reaction/degradation processes. In Paper II we highlighted the serious scarcity in physicochemical property data for the alternative FRs and demonstrated the applicability of a simple QSPR technique for selecting reliable property estimates for chemical assessments. A modelling fate assessment indicated a strong partitioning to indoor surfaces and dust for most of the alternative FRs. Indications for POP (persistent organic pollutant)-like persistence and LRT (long-range transport) and bioaccumulative potential in the outdoor environment were also identified for many alternative FRs. Using an inverse modelling approach in Paper III we estimated 2 to 3 orders of magnitude higher emissions of organophosphate FRs (0.52 and 0.32 ng.h-1) than brominated FRs (0.083 μg.h-1 and 0.41 μg.h-1) in Norwegian households. An emission-to-dust signal was also identified for organophosphate FRs suggesting that direct migration to dust may be a key fate process indoors. No evidence of a direct source-to-dust transfer mechanism was seen in Paper IV where the chemical transfer between a product treated with an organophosphate FR and dust in direct contact was experimentally investigated. It was concluded though that direct contact between an FR source and dust can result in contamination hotspots indoors. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.</p>
6

Nanoporous Materials for Carbon Dioxide Separation and Storage

Varela Guerrero, Victor 2011 May 1900 (has links)
Global climate change is one of the most challenging problems that human beings are facing. The large anthropogenic emission of CO2 in the atmosphere is one of the major causes for the climate change. Coal-fired power plants are the single-largest anthropogenic emission sources globally, accounting for approximately one third of the total CO2 emissions. It is therefore necessary to reduce CO2 emission from coal-fired power plants. Current technologies for the post-combustion CO2 capture from flue gas streams can be broadly classified into the three categories: absorption, adsorption, and membrane processes. Despite challenges, CO2 capture by adsorption using solid sorbents and membranes offers opportunities for energy-efficient capture and storage of CO2. Nanoporous materials have attracted tremendous interest in research and development due to their potential in conventional applications such as catalysis, ion-exchange, and gas separation as well as in advanced applications such as sensors, delivery, and micro-devices. In the first part of this dissertation, we will study the synthesis of membranes using an emerging class of nanoporous materials, metal-organic frameworks (MOFs) for carbon dioxide (CO2) separations. Due to the unique chemistry of MOFs which is very different from that of zeolites, the techniques developed for the synthesis of zeolite membranes cannot be used directly. In order to overcome this challenge, a couple of novel techniques were developed: 1) "thermal seeding" for the secondary growth and 2) "surface modification" for the in situ growth. Membranes of HKUST-1 and ZIF-8, two of the most important MOFs, were prepared on porous α-alumina supports using thermal seeding and the surface modification techniques, respectively. The second part of this dissertation demonstrates a simple and commercially viable application of nanoporous materials (zeolite 5A and amine-functionalized mesoporus silica), storing CO2 as a micro-fire extinguishers in polymers. Materialist is observed that by dispersing these highly CO2-philic nanoporous materials in polymer matrices, the propagation of flame was greatly retarded and extinguished. This flame retarding behavior is attributed to the fact that CO2 released from the sorbents (zeolite 5A and mesoporous silica), blocks the flow of oxygen, therefore causing the fire to be effectively extinguished. Our results suggest that the binding strength of CO2 on sorbents play an important role. If the binding strength of CO2 is too low, CO2 releases too early, thereby ineffective in retarding the flame.
7

Effects of Four New Brominated Flame Retardants on Hepatic Messenger RNA Expression, In Vitro Toxicity and In Ovo Toxicity in the Domestic Chicken (Gallus gallus)

Egloff, Caroline 09 May 2011 (has links)
Brominated flame retardants (BFR) such as hexachlorocyclopentadienyl-dibromocyclooctane (HCDBCO), bis(2-ethylhexyl)tetrabromophthalate (BEHTBP), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) and decabromodiphenylethane (DBDPE) are contaminants of environmental concern. These BFRs are replacement alternatives for some of the major production BFRs, which have been restricted from the marketplace due to their adverse health effects. Their presence in environmental matrices, including wild birds, suggests they should be tested for possible toxic effects. BFR alternatives have been detected in the eggs of colonial fish-eating birds, suggesting maternal transfer during ovogenesis and the potential for these chemicals to bioaccumulate through the food chain. However, information regarding the toxicity of HCDBCO, BEHTBP, BTBPE and DBDPE exposure in birds is lacking. This thesis consisted of a combined in vitro/in ovo approach to determine: 1) the concentration-dependent effects of these four BFR alternatives in chicken embryonic hepatocytes (CEH), and 2) the dose-dependent effects of HCDBCO and BTBPE in chicken embryos following injection into the air cell of eggs prior to incubation. Changes in the mRNA expression levels of genes previously found to be responsive to other BFRs were assessed in CEH and liver tissue, in addition to examining overt toxicity (i.e. cytotoxicity, pipping success). None of the BFRs tested were cytotoxic up to 60 µM HCDBCO, 60 µM BEHTBP, 1.4 µM BTBPE or 0.2 µM DBDPE in CEH. Injection doses up to 50 µg/g egg HCDBCO and 10 µg/g egg BTBPE had no effect on embryonic pipping success. The accumulation of HCDBCO and BTBPE was variable in liver and did not follow a linear uptake pattern with respect to injection dose, due in part to difficulties with the solubility of these chemicals in the dimethyl sulfoxide (DMSO) vehicle. In, CEH, HCDBCO caused a decrease in CYP1A4/5 mRNA at all concentrations tested, while CYP2H1 and CYP3A37 were induced only at 10 µM. In contrast, only TTR mRNA was down-regulated in hepatic tissue at all injection concentrations of HCDBCO. The highest concentration of BTBPE induced CYP1A4/5 mRNA to 115- and 18-fold in CEH, and 6.5- and 1.8-fold in liver tissue. In vitro and in ovo exposure to BTBPE caused a concentration-dependent decrease in DIO3 mRNA, while CYP3A37 was down-regulated 2-fold at 10 µg/g in liver tissue. In CEH, DBDPE induced CYP1A4/5 mRNA to a maximum of 29- and 59-fold at 0.2 µM, and increases in DIO1 mRNA and decreases in CYP3A37 mRNA were also observed. None of the gene targets were responsive to BEHTBP exposure in CEH. This is the first study to report on the toxicological and molecular effects of HCDBCO, BEHTBP, BTBPE and DBDPE in an avian species. Using this combined in vitro/in ovo approach has permitted the characterization of these four BFR alternatives by defining possible mechanisms of biological action in a model avian species, the chicken.
8

Effects of Four New Brominated Flame Retardants on Hepatic Messenger RNA Expression, In Vitro Toxicity and In Ovo Toxicity in the Domestic Chicken (Gallus gallus)

Egloff, Caroline 09 May 2011 (has links)
Brominated flame retardants (BFR) such as hexachlorocyclopentadienyl-dibromocyclooctane (HCDBCO), bis(2-ethylhexyl)tetrabromophthalate (BEHTBP), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) and decabromodiphenylethane (DBDPE) are contaminants of environmental concern. These BFRs are replacement alternatives for some of the major production BFRs, which have been restricted from the marketplace due to their adverse health effects. Their presence in environmental matrices, including wild birds, suggests they should be tested for possible toxic effects. BFR alternatives have been detected in the eggs of colonial fish-eating birds, suggesting maternal transfer during ovogenesis and the potential for these chemicals to bioaccumulate through the food chain. However, information regarding the toxicity of HCDBCO, BEHTBP, BTBPE and DBDPE exposure in birds is lacking. This thesis consisted of a combined in vitro/in ovo approach to determine: 1) the concentration-dependent effects of these four BFR alternatives in chicken embryonic hepatocytes (CEH), and 2) the dose-dependent effects of HCDBCO and BTBPE in chicken embryos following injection into the air cell of eggs prior to incubation. Changes in the mRNA expression levels of genes previously found to be responsive to other BFRs were assessed in CEH and liver tissue, in addition to examining overt toxicity (i.e. cytotoxicity, pipping success). None of the BFRs tested were cytotoxic up to 60 µM HCDBCO, 60 µM BEHTBP, 1.4 µM BTBPE or 0.2 µM DBDPE in CEH. Injection doses up to 50 µg/g egg HCDBCO and 10 µg/g egg BTBPE had no effect on embryonic pipping success. The accumulation of HCDBCO and BTBPE was variable in liver and did not follow a linear uptake pattern with respect to injection dose, due in part to difficulties with the solubility of these chemicals in the dimethyl sulfoxide (DMSO) vehicle. In, CEH, HCDBCO caused a decrease in CYP1A4/5 mRNA at all concentrations tested, while CYP2H1 and CYP3A37 were induced only at 10 µM. In contrast, only TTR mRNA was down-regulated in hepatic tissue at all injection concentrations of HCDBCO. The highest concentration of BTBPE induced CYP1A4/5 mRNA to 115- and 18-fold in CEH, and 6.5- and 1.8-fold in liver tissue. In vitro and in ovo exposure to BTBPE caused a concentration-dependent decrease in DIO3 mRNA, while CYP3A37 was down-regulated 2-fold at 10 µg/g in liver tissue. In CEH, DBDPE induced CYP1A4/5 mRNA to a maximum of 29- and 59-fold at 0.2 µM, and increases in DIO1 mRNA and decreases in CYP3A37 mRNA were also observed. None of the gene targets were responsive to BEHTBP exposure in CEH. This is the first study to report on the toxicological and molecular effects of HCDBCO, BEHTBP, BTBPE and DBDPE in an avian species. Using this combined in vitro/in ovo approach has permitted the characterization of these four BFR alternatives by defining possible mechanisms of biological action in a model avian species, the chicken.
9

Phthalates and polybrominated diphenyl ethers in retail stores

Urquidi, Jorge Rodolfo 24 April 2013 (has links)
Retail stores are an environment with a rich diversity of toxic chemicals typically found in consumer products. Among these chemicals, semi-volatile organic compounds (SVOCs) are an important class with great health concerns. Phthalates and polybrominated diphenyl ethers (PBDEs) are high production volume SVOC chemicals pervasively used in plastics and other consumer products. Exposure to them may cause serious adverse health effects, including endocrine disruption. They, however, have not been widely studied in retail environments. In this study, indoor air samples were collected from 15 retail stores in Austin, TX and University Park, PA. Some of these stores were revisited on different temperate seasons to account for weather variability. Indoor concentrations of the most ubiquitous pollutants were correlated with several building characteristics, including retailer type, temperature, and building use characteristics. Collected data shows a wider variety of phthalates and PBDEs, as well as higher indoor airborne concentrations for large department stores as compared to grocery stores, which typically have fewer sources in comparison. / text
10

Environmental Fate and Toxicity of Three Brominated Flame Retardants in Aquatic Mesocosms

de Jourdan, Benjamin, Hanson, Mark, Muir, Derek, Sibley, Paul, Solomon, Keith 10 September 2012 (has links)
Tradtional brominated flame retardants (BFRs), namely the polybrominated diphenyl ethers (PBDEs), have persistent, bioaccumulative, and toxic properties that have resulted in the phase out of their production and their be banned in certain jurisdictions. To meet regulatory flame retardancy requirements, non-PBDE BFRs have entered the marketplace. Much remains unknown regarding the environmental fate and toxicity of these emerging BFRs. The objective of this thesis was to use outdoor mesocosms to examine the fate and toxicity of three emerging BFRs; bis(tribromophenoxy)ethane (BTBPE), tetrabromobisphenol A bis(dibromopropyl ether) (TBBPA-DBPE), and BZ-54, which consists of two BFRs, ethylhexyl-tetrabromobenzoate (EHTeBB) and bis(ethylhexyl)tetrabromophthalate (BEHTBP). While it was difficult to accurately determine degradation rates because of fluctuating concentrations, the estimated half-lives indicated these compounds are persistent (> 60 days in sediments). The partitioning of the compounds between the particulates and the sediment resulted in differential degradation rates (greater in the particulates), and products formed; those formed on the particulates were consistent with photodegradation products. The effects of these emerging BFRs on Hyalella azteca and the benthic macroinvertebrate community were assessed through the use of in situ exposure and sampling techniques. The in situ Hyalella cages showed a high degree of variability for most endpoints, regardless of their placement (e.g., water column vs. sediment) in the mesocosm. BTBPE accumulated in the H. azteca (0.03 – 1.4 ng/g ww), however this was not associated with any changes in growth or reproduction. There was high variability in abundance and diversity between the mesocosms, which limited the ability to detect statistically significant differences. Interestingly, the BZ-54 treated mesocosms had the greatest abundance, and the least amount of community diversity. This thesis examined the bioaccumulation potential of these compounds in fathead minnow (Pimephales promelas), as well as the associated effects on growth and development as measured through physical and biochemical endpoints. There was considerable uptake and persistence of BTBPE and TBBPA-DBPE, as well as indication of metabolism of these compounds, but limited physical effects observed. There were indications of increased oxidative stress in the BZ-54 treatment, and increased induction of vitellogenin in fathead minnow from the BTBPE treatment. / Environment Canada's Chemicals Management Plan

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