Flame retardant (FR) intumescent additives and montmorillonite (MMT) organoclay incorporated nylon-6 nanocomposite (FR-NC-PA6) fibers with a diameter of about 200 nm were fabricated by electrospinning. Before electrospinning, dispersion and exfoliation of the FR additive and MMT in nylon-6 were achieved by twin-screw extrusion. Tensile, TGA and UL-94 flammability tests were first performed using injection-molded bulk samples. The tensile modulus of FR-NC-PA6 was 45% higher than that of neat PA6, but tensile strength and elongation at break decreased by 23% and 98.7%, respectively. It is worth noting that although the TGA results show that FR-NC-PA6 has a slightly earlier decomposition temperature than neat PA6, it did not drip under fire and had the best rating (V-0) in UL 94 test, while neat PA6 is only rated as V-2. SEM and EDX of char residues after the UL 94 test clearly show the oxygen-rich protective char layer on the surface. These results indicate the advantage of using clay and FR additive in bulk-form PA6. Flammability of electrospun nanocomposite fibers was characterized by Micro-combustion calorimeter (MCC), a small-scale test to screen flammability of polymer materials. The MCC results show that the nano-fillers in both bulk and fiber form could effectively improve flame retardant properties of the material. Electrospun fibers had similar combustion properties as bulk materials. In addition to FR applications, superhydrophobic surface was another area that was explored using the electrospun nanocomposite fibers. Static water contact angle (WCA) test showed that samples with 5wt% clay even without plasma treatment greatly improved the WCA to 140°, probably due to the barrier effect of nanoclay platelets. Plasma treatment was used to modify the surface energy, further improving WCA to as high as 160°. However, fiber structure was partially etched away when overexposed to the plasma. This etching effect increased the surface roughness. Clay incorporated samples had higher level of surface roughness and better resistance to plasma etching compared to neat nylon 6. / text

De récentes études ayant pointé les potentiels effets de perturbation endocrinienne d’esters organophosphorés (OPE), dont l’utilisation globale en tant que retardateurs de flamme et plastifiants est en constante augmentation, font apparaître le besoin d’une évaluation approfondie des risques. Malgré des efforts passés pour l'analyse de ces contaminants ré-émergents dans divers compartiments environnementaux abiotiques, peu d'informations sont disponibles pour le biote, en partie en raison de l'absence de stratégie analytique efficace. La thèse visait d'abord à développer une stratégie d'analyse robuste dédiée à l’analyse d’une large gamme d'OPE à l’état de traces dans le poisson et d’autres denrées alimentaires. La stratégie retenue est basée sur l'extraction liquide sélective sous pression et la chromatographie par perméation de gel. La détection a été réalisée par chromatographie en phase gazeuse couplée à la spectrométrie de masse en tandem, avec ionisation par impact électronique ou chimique à pression atmosphérique, cette dernière étant plus spécifique et innovante. Le second objectif visait à produire des données de prévalence originales et utiles à l'évaluation de l'exposition en France. Des jeux de poissons et de denrées emballées ont présenté des niveaux totaux inférieurs à 10 et jusqu'à 100 ng/g pf, respectivement. Une première exploitation des données sur poissons en termes d'évaluation quantitative de risque pour l’Homme a dévoilé des ratios de risques faibles au regard de données toxicologiques disponibles. Néanmoins, des données complémentaires sur l'exposition et la toxicologie seront indispensables pour conclure quant aux implications en santé publique. / As recent studies highlighted that several organophosphate esters (OPEs) exhibit potential endocrine disrupting effects, in-depth risk assessment is required, when their global use as flame retardants and plasticizers is considerably increased. Despite previous efforts on the analysis and exposure assessment of these re-emerging contaminants in various abiotic environmental compartments, still limited information is available in biota samples, partly due to the lack of efficient analytical strategies. The thesis aimed first at developing a robust analytical strategy dedicated to the determination of a wide range of OPEs at trace levels in fish and other foodstuffs. The developed strategy involved selective pressurized liquid extraction with Florisil® as lipid sorbent, followed by further purification step by gel permeation chromatography. The extract analysis was then performed by gas chromatography coupled to tandem mass spectrometry fitted with electron impact or atmospheric pressure chemical ionisation mode, the latter being a more specific and innovative approach. The second aim was to apply the developed strategy to produce original occurrence data that can be useful for exposure assessment at the French level. Fish sample sets exhibited levels below 10 ng/g fw while packaged foodstuffs presented levels up to 100 ng/g fw. A first interpretation of these data in terms of dietary human quantitative risk assessment through fish consumption tended to show low risk ratios in connection with available toxicological data. However, additional exposure and toxicological data is required before any conclusions regarding public health implication can be drawn

The fire behaviour of linear low-density polyethylene composites containing 10 wt.% of different carbon-based fillers was studied. Cone calorimeter tests conducted at a heat flux of 35 kW_m_2 showed that the expandable graphite sample reduced the peak heat release rate by about 50 % while the flake graphite increased the ignition time by about 80 %. Pyrolysis combustion flow calorimetry results were practically identical for all composites. This reveals shortcomings of this bench-scale flammability test method when the flame retardancy mechanisms relies on either the development of physical barrier layer at the surface of the burning sample or on reflecting the incident heat flux. Similarly, it was found that laser pyrolysis-thermogravimetric analysis generated outcomes that did not correlate with the cone calorimeter results at all. In particular, the composite based on expandable graphite performed poorly. The likely explanation is that the aspect ratios of the small samples were such that the barrier effects on which this system relies, was negated by edge effects. / Dissertation (MSc)--University of Pretoria, 2018. / Chemical Engineering / MSc / Unrestricted

Flame-retardant coatings have been serving their purpose since the romans ruled Europe. These products have been developed through the years, by mixing and synthetizing solutions, which have resulted in effective, although questionable, products due to their impact on the environment and our health. This matter has been addressed earlier, predominantly regarding fabrics. Now is the time to approach this issue by finding an environmentally and health friendly flame-retardant, that can be applied on wood. Phytic acid is a phosphorus based organic compound which is found abundant in nature and could potentially act as a non-toxic flame-retardant. The acid can form other complexes which could add additional flame-retardant mechanisms and desired characteristics of a flame-retardant. This potential flame-retardant was investigated using two different methods. The first method includes two test series which sought to explain how properties as concentration of phytic acid, pH and different additives affected flame-retardant behaviour. The first method was later changed and refined into the second method, to add higher reliability and validity to the conducted tests. The new method implemented additional analytical methods such as differential scanning calorimetry and nuclear magnetic resonance spectroscopy to investigate particular compounds. The results from the thermogravimetric analysis show that wood samples which were coated with the flame-retardant, had twice the mass percentage remaining compared to the untreated wood samples.

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<p>In the work underlying this thesis solid-phase microextraction (SPME) was evaluated as a passive sampling technique for organophosphate triesters in indoor air. These compounds are used on a large scale as flame-retarding and plastizicing additives in a variety of materials and products, and have proven to be common pollutants in indoor air. The main objective of this work was to develop an accurate method for measuring the volatile fraction. Such a method can be used in combination with active sampling to obtain information regarding the vapour/particulate distribution in different indoor environments. SPME was investigated under both equilibrium and non-equilibrium conditions and parameters associated with these different conditions were estimated. </p><p>In <b>Paper I</b>, time-weighted average (TWA) SPME under dynamic conditions was investigated in order to obtain a fast air sampling method for organophosphate triesters. Among the investigated SPME coatings, the absorptive PDMS polymer had the highest affinity for the organophosphate triesters and was consequently used in all further work. Since the sampling rate is dependent on the agitation conditions, the linear airflow rates had to be carefully considered. Sampling periods as short as 1 hour were shown to be sufficient for measurements in the ng-μg m^-3 range when using a PDMS 100-μm fibre and a linear flow rate above 7 cm s^-1 over the fibre. </p><p>SPME under equilibrium conditions is rather time-consuming, even under dynamic conditions, for slowly partitioning compounds such as organophosphate triesters. Nevertheless, this method has some significant advantages. For instance, the limit of detection is much lower compared to 1 h TWA sampling. Furthermore, the sampling time can be ignored as long as equilibrium has been attained. In <b>Paper II</b>, SPME under equilibrium conditions was investigated and evaluated for organophosphate triester vapours. Since temperature and humidity are closely associated with the distribution constant a simple study of the effect of these parameters was performed. The obtained distribution constants were used to determine the air levels in a common indoor environment. SPME and parallel active sampling on filters yielded similar results, indicating that the detected compounds were almost entirely associated with the vapour phase</p><p>To apply dynamic SPME method in the field a sampler device, which enables controlled linear airflow rates to be applied, was constructed and evaluated (<b>Paper III</b>). This device was developed for application of SPME and active sampling in parallel.</p><p>A GC/PICI-MS/MS method was developed and used in combination with active sampling of organophosphate triesters in indoor air (<b>Paper IV</b>). The combination of MS/MS and the soft ionization achieved with methanol as reagent gas yielded high selectivity and detection limits comparable to those provided by GC with nitrogen-phosphorus detection (NPD). The method limit of detection, when sampling 1.5 m³ of air, was in the range 0.1-1.4 ng m^-3. In <b>Paper V</b>, the developed MS method was used in combination with SPME for indoor air measurements.</p><p>The levels detected in the investigated indoor environments range from a few ng to μg m^-3. Tris(2-chloropropyl) phosphate was detected at a concentration as high as 7 μg m^-3 in a newly rebuilt lecture room.</p>

<p>Following the phase out of polybrominated diphenyl ethers (PBDEs), manufacturers turned to several alternative flame retardants (FRs) to meet flammability standards. Organophosphate FRs (OPFRs), and in particular tris (1,3-dichloropropyl) phosphate (TDCPP), have been increasingly detected in textiles and foam padding used in a variety of consumer products including camping equipment, upholstered furniture, and baby products. Like PBDEs, OPFRs are additive, meaning that they are not chemically bound to the treated material and can more readily leach out into the surrounding environment. Indeed, OPFRs have been detected in numerous environmental and biological matrices, often at concentrations similar to or exceeding that of PBDEs.</p><p>Although OPFRs have been in use for several decades, relatively little is known regarding their potential for adverse human and environmental health consequences. However, based on their structural similarity to OP pesticides, they may have analogous mechanisms of toxicity. OP pesticide toxicity is classically associated with cholinesterase inhibition, resulting in cholinergic intoxication syndrome. OPFRs have been shown to be ineffective cholinesterase inhibitors, however chlorpyrifos (CPF) and other OP pesticides have been shown to elicit adverse effects on developing organisms through other mechanisms.</p><p>The main objective of this research project was to evaluate the toxicity of four structurally similar OPFRs (TDCPP; tris (2,3-dibromopropyl) phosphate, (TDBPP); tris (1-chloropropyl) phosphate (TCPP) and tris (2-chloroethyl) phosphate (TCEP)) in comparison to chlorpyrifos (CPF), a well-studied OP pesticide. A combination of in vitro and in vivo models was used to elucidate potential mechanisms as well as functional consequences of exposure in developing organisms. </p><p>In the first research aim, a series of in vitro experiments with neurotypic PC12 cells was used to evaluate the effects of four structurally similar OPFRs (TDCPP, TDBPP, TCEP, or TCPP) and CPF on neurodevelopment. The effects of TDCPP were also compared to that of BDE-47, a major component of the commercial PentaBDE mixture. In general, TDCPP elicited similar or greater effects when compared to an equimolar concentration of CPF. All OPFRs tested produced similar decrements in cell number and altered phenotypic differentiation, while BDE-47 had no effect on cell number, cell growth, or neurite growth. </p><p>For the second research aim, zebrafish (Danio rerio) were used to evaluate the effects of the same suite of chemicals on early development. TDCPP, TDBPP, and CPF elicited overt toxicity (e.g., malformations or death) within the concentration range tested (0.033-100 µM). TDBPP was the most potent with 100% mortality by 6 days post fertilization (dpf) at &#8805;3.3 µM. CPF and TDCPP showed equivalent toxicity with malformations observed in at 10 µM and significant mortality (&#8805;75%) at &#8805;33 µM. There was no overt toxicity among TCEP- and TCPP-exposed fish. All test chemicals affected larval swimming behavior on 6 dpf at concentrations below the overt toxicity threshold. Parent chemical was detected in all in embryonic (1 dpf) and larval (5 dpf) tissues. TDCPP and TDBPP showed rapid and extensive metabolism.</p><p>Finally, for the third aim, juvenile (45-55 dpf) zebrafish were exposed to CPF (1 µg/g food) or TDCPP (Low TDCPP = 1 µg/g food; High TDCPP = 40 µg/g food) via diet for 28 days followed by a 7 day depuration period where all treatments received clean food. A dietary exposure was chosen to more closely recapitulate exposure in humans. Samples were collected at seven time points throughout the experiment: days 0, 7, 14, 21, 28, 30, 35. Whole tissues were collected for tissue accumulation and histopathology endpoints. Viscera and brain were dissected and flash frozen separately for DNA damage analyses. </p><p>Tissue measurements of CPF, TDCPP, and the metabolite bis (1,3-dichloropropyl) phosphate (BDCPP) were often below the method detection limit, however when present there was a trend towards increased accumulation with treatment and time. On Day 7 Low TDCPP caused a dramatic but transient increase in DNA damage in both viscera and brain that returned to control levels by Day 14. Similar results have been seen previously with other genotoxicants and may be due to CPF and High TDCPP inducing an adaptive response prior to the 7 day sampling point. All treatments shifted the neurohypophysis to adenohypophysis ratio (NH/AH; Day 7 only) and significantly increased thyroid follicle activation (Day 14). Finally High TDCPP affected gonad maturation, causing a significant increase in ovary follicle development (Day 14) and a transient but marked decrease in testes maturity (Day 7). Taken together these data suggest that dietary exposure to TDCPP and CPF elicits DNA damage in brain and viscera and alters endocrine function in juvenile zebrafish. Importantly, analyses were restricted to the first three time points (Days 0, 7, and 14) due to the emergence a disease among the experimental colony. Although these samples were collected prior to the disease becoming apparent, it remains a potential confounder of the current results.</p> / Dissertation

O PVC é um dos principais polímeros termoplásticos da atualidade graças à sua grande versatilidade. Entretanto, uma de suas características é a baixa estabilidade térmica, sendo necessário o emprego de aditivos em sua estrutura. Uma das maiores preocupações mundiais é a segurança, sendo que muitos produtos levam proteção anti-chama em sua composição. Entre os vários agentes retardadores de chama a grafite aparece como um material promissor e pouco estudado. No presente trabalho foi estudada uma série de grafites com propriedades anti-chama oriundas de óxido de grafite \"flake\". O óxido de grafite foi submetido a vários tratamentos térmicos em atmosfera para a obtenção de grafites expandidas. O comportamento anti-chama dessas grafites foi testado adicionando-se 20% em peso no PVC. Membranas desses compósitos foram preparadas utilizando-se um \"doctor blade\". Os compósitos de grafites produzidas foram caracterizados por microscopia de varredura eletrônica e análise térmica. Isotermas de adsorção/dessorção de N2 também foram coletadas para determinação de área superficial específica e distribuição de poros. A grafite com melhores propriedades anti-chama foi aquela obtida em temperatura mais elevada, 900oC, ou seja, a grafite com mais elevada área superficial específica e com maior capacidade de produção de fuligem. / PVC is one of the most important thermoplastic polymers because of its versatility. However, like other polymers, for many technological uses, there is a need to enhance its thermal stability. Security is a global concern, so, the use of some fire retardants is required in polymer composites. Expanded graphite appears as a cleaner type of fire retardants, not well known yet. In the present work, expanded graphite obtained from the graphite oxide was studied. It were prepared PVC composite-membranes with 20 weight % of expanded graphite employing Doctor Blade. The samples were characterized by scanning electron microscope, thermogravimetric analysis and N2 adsorption/desorption isotherms were also collected for the determination of specific surface area and porous distribuition. The results show that the best fire retardant behaviour was achieved by the expanded graphite at 900oC, the graphite with the higher specific surface area and with the largest capacity of soot production.

Fungal contamination of buildings poses numerous challenges to researchers, building owners and occupants. Public health agencies promote prevention and remediation of mold and water damage, but lack sensitive methods to detect hidden mold growth and a complete understanding of the biological mechanisms that make occupying moldy buildings a hazard. The wide spread use of the fire retardant antimony trioxide (Sb2O3) on building materials and furnishings makes it inevitable that mold growth on treated materials will occur in some buildings with water damage. Several authors have speculation that microbial growth on materials treated with antimony trioxide could mobilize antimony through a volatile intermediate, trimethylstibine. The purpose of this study was to determine if fungal growth on a commonly used building material that contains antimony trioxide, fiberglass ductboard, results in the mobilization and release of antimony compounds. Additionally, CO2 generation rates were determined during fungal growth on fiberglass ductboard and gypsum wallboard. Results demonstrated a significant reduction of antimony concentration in fiberglass ductboard after fungal growth had occurred. Antimony emission rates and resulting concentrations of antimony oxide aerosols were estimated using an indoor mass balance mathematical model. Concentrations of CO2 were also modeled within a wall cavity and static HVAC ducts to determine if fungal growth could elevate CO2 levels above ambient concentrations. Although volatile phase antimony was not detected in chamber experiments, probably due to rapid oxidation and high humidity, mobilization of antimony trioxide from fiberglass ductboard components was demonstrated in several experiments. Indoor Air modeling of a residence suggest that concentrations of antimony could, under worst case conditions, exceed the reference concentration (RfC) of antimony trioxide by 10 to 1,000 times. These results suggest that biomethylation and mobilization of antimony by mold growth on building materials could result in elevated occupant exposures to antimony compounds. Antimony is a known respiratory irritant that can be similar to arsenic in its toxicity. Modeling results also suggest that elevated carbon dioxide concentrations due to fungal metabolic respiration are variable and dependent on environmental conditions. Measuring elevated carbon dioxide concentrations to detect hidden fungal growth was determined to not be a predictive assessment tool.