Photo-oxidatative degradation in isotactic polypropylene (PP) has been examined in samples made by both injection and compression moulding and using different moulding conditions. Samples were exposed to ultraviolet (UV) radiation in the laboratory for periods up to 48 weeks. The specimens were tested in tension and the fracture surfaces were inspected by scanning electron microscopy. The extent of chemical degradation was assessed by gel permeation chromatography and Fourier transform infrared spectroscopy. The structural characterization of the as-moulded and UV-exposed materials was conducted by differential scanning calorimetry, X-ray diffraction, pole figure analysis, and polarized light microscopy. Filled grades of PP containing talc were also investigated. The mechanical properties of degraded PP were shown to be highly dependent on aspects like the extent and depth-profile of degradation, the character of the polymer physical structure, and the presence of filler and nucleating agent. Injection moulded bars containing weld lines were also investigated, and their mechanical properties were generally poorer than those for equivalent samples without weld regions. With most samples studied here a partial recovery in tensile properties was observed after 6-9 weeks exposure. Analysis of the fracture surfaces indicated that in the specimens with better properties the surface cracks did not propagate into the undegraded interior. An increase in the polymer crystallinity was observed during exposure, caused by rearrangement of molecule segments released by oxidative scission in the non-crystalline region. This process, called chemi-crystallization, continues until a large number of chemical defects is present within the molecules, and it results in surface cracks formed spontaneously during exposure. In injection moulded samples the pattern of surface cracks featured circular arcs radiating from the injection gate and they were correlated with the flow lines generated during mould filling. The concentration of surface cracks in these samples varied with the location in the test bar, according to local variations in crystal orientation. The crystallization of photodegraded PP from the melt was investigated under isothermal and non-isothermal conditions. The kinetics of crystallization, degree of crystallinity, and morphology were shown to depend on the molecular weight and on the presence of chemical impurities within the molecules. The crystal y-phase was formed in specimens exposed for more than 18 weeks. Double peaks were normally observed in DSC heating experiments of unfilled polypropylene and were assigned to crystal re-organization during heating. The existence of different molecule species was detected by DSC and light microscopy, and might also have contributed to the melting behaviour.

The effect of light on a model colloidal beverage system under two different test conditions, refrigerated storage (14 d, 4°C) and accelerated storage at room temperature (12 hr, 25°C), was investigated. The addition of lutein to provide protection against photo-oxidation of susceptible compounds also was investigated. Fluorescent light-exposure (14 d, 4°C) of the control beverage system led to a decline in sensory quality based on triangle test results. Sensory quality also declined in the lutein-fortified beverage due to light-exposure. Sensory quality of light-exposed, lutein-fortified beverage compared to the light-protected control did not yield significant sensory differences for two out of three replications giving positive implications towards the use of lutein for photo-protection. Overall, panelists preferred beverages that were protected from light exposure with no specific preference towards control or lutein-fortified beverage, indicating lutein did not inhibit photo-chemical reactions leading to a decline in sensory quality. Chemical analysis showed limonene concentration was significantly higher in the lutein-fortified beverage compared to the control beverage after light exposure (14 d, 4°C). Hexanal concentration, however, was not closely correlated with sensory differences. Results of the accelerated storage (12 hr, 25°C) study showed that the most damaging wavelengths to lutein stability were UV (200-400 nm) and 463 nm wavelengths. Degradation of lutein at 463 nm was expected and can be attributed to lutein''s absorption of blue light at 450 nm. Hexanal formation was highest in the control beverage when exposed to full spectrum light and specifically UV (200-400 nm) wavelengths. Hexanal was also formed in the lutein-fortified beverage under full spectrum light and UV (200-400 nm) wavelength but to a significantly lesser degree. Limonene degraded significantly under all treatment conditions, with the most occurring during full spectrum light exposure. Lutein-fortification did not effectively protect limonene from degradation under these conditions. / Master of Science in Life Sciences

No description available.

No description available.

abstract: Black carbon (BC) is the product of incomplete combustion of biomass and fossil fuels. It is found ubiquitously in nature and is relevant to studies in atmospheric science, soil science, oceanography, and anthropology. Black carbon is best described using a combustion continuum that sub-classifies BC into slightly charred biomass, char, charcoal and soot. These sub-classifications range in particle size, formation temperature, and relative reactivity. Interest in BC has increased because of its role in the long-term storage of organic matter and the biogeochemistry of urban areas. The global BC budget is unbalanced. Production of BC greatly outweighs decomposition of BC. This suggests that there are unknown or underestimated BC removal processes, and it is likely that some of these processes are occurring in soils. However, little is known about BC reactivity in soil and especially in desert soil. This work focuses on soot BC, which is formed at higher temperatures and has a lower relative reactivity than other forms of BC. Here, I assess the contribution of soot BC to central AZ soils and use the isotopic composition of soot BC to identify sources of soot BC. Soot BC is a significant (31%) fraction of the soil organic matter in central AZ and this work suggests that desert and urban soils may be a storage reservoir for soot BC. I further identify previously unknown removal processes of soot BC found naturally in soil and demonstrate that soil soot BC undergoes abiotic (photo-oxidation) and biotic reactions. Not only is soot BC degraded by these processes, but its chemical composition is altered, suggesting that soot BC contains some chemical moieties that are more reactive than others. Because soot BC demonstrates both refractory and reactive character, it is likely that the structure of soot BC; therefore, its interactions in the environment are complex and it is not simply a recalcitrant material. / Dissertation/Thesis / Ph.D. Chemistry 2013

Este trabalho é direcionado ao estudo dos efeitos da radiação UV sobre amostras de poliestireno (PS) e de copolímeros de estireno com proporções variáveis de 2-trimetilsililóxi-1,3-butadieno (TSB, I), 2-metóxi-1,3-butadieno (MEB, II) e 2-etóxi-1,3-butadieno (ETB, III), em solução aerada, visando principalmente à amplificação da degradação ambiental do PS quando exposto a condições de intemperismo natural. (Ver no arquivo em PDF). Os polímeros foram sintetizados via polimerização radicalar em solução, resultando em uma massa molar ponderai média (Mw) de cerca de 30,0 kg/mol para o homo e copolímeros. Estes produtos, após serem submetidos a um processo de hidrólise na presença de fluoreto de tetrabutilamônio (série TSB) ou HCI aquoso (séries MEB e ETB), resultaram em PS contendo grupos carbonila na cadeia principal sendo, a seguir, isolados e caracterizados por meio de técnicas analíticas como espectroscopia de infravermelho (IR), análise elementar, cromatografia de exclusão por tamanho (SEC), espalhamento de luz estático dependente do tempo (TDSLS), análise térmica (TG e DSC) e microscopia eletrônica de varredura (MEV). As soluções poliméricas foram irradiadas com lâmpada de mercúrio de baixa pressão (99,5% de emissão a 254 nm), na presença de ar e à temperatura ambiente, por um período de dez horas. As alterações sofridas pelos polímeros foram acompanhadas por meio de medidas de IR, TDSLS e SEC. Os espectros no infravermelho mostraram um aumento contínuo da intensidade de algumas bandas: na região entre 3800 - 3000 cm-1, houve um alargamento das bandas que pode ser atribuído à formação de grupos hidroxila e/ou hidroperóxido; na região de 1900 - 1500 cm-1, observou-se o aparecimento de um ombro em 1712 cm-1, que pode ser atribuído à formação de grupos cetona e aldeído como funções terminais na cadeia do polímero e, na região entre 1500 - 1000 cm-1, o alargamento das bandas foi atribuído à formação de grupos anidrido. Os estudos realizados por TDSLS revelaram claramente que os copolímeros degradam com mais rapidez que o PS puro, e as taxas de degradação aumentam proporcionalmente ao aumento no teor de carbonilas incorporadas ao polímero. Tal observação tem suporte nas massas molares ponderais médias obtidas via SEC (Mw) dos fragmentos resultantes da fotólise, com valores cada vez menores com o aumento dos efeitos da fotodegradação, iniciando com cerca de 34,0 kg/mol (TSB5), por exemplo, e decrescendo a valores de Mw tão baixos quanto 4,8 kg/mol (TSB15). Para finalizar, tentou-se verificar o comportamento dos polímeros quando expostos a condições reais de utilização, submetendo-se corpos de prova a um envelhecimento acelerado em câmara de intemperismo artificial e avaliando seu comportamento mecânico. Os resultados mostraram que, para homo e copolímeros, houve uma redução na resistência à tração com o aumento do tempo de exposição (0 a 600 horas), sendo este efeito muito mais acentuado para os copolímeros. / This work was directed to the study of the UV radiation effects upon samples of polystyrene (PS) and copolymers of styrene with different fractions of 2-trimethylsililoxy-1,3-butadiene (TSB, I), 2-methoxy-1 ,3-butadiene (MEB, II) and 2-ethoxy-1,3-butadiene (ETB, III), in normally aerated solution, aiming at the optimization of the PS degradation when exposed to weathering conditions. (See in the PDF file). The polymers were prepared by free-radical polymerization in solution, resulting in average molecular weight (Mw) of about 30.0 kg/mol for the homo and copolymers. The resulting polymers were submitted to hydrolysis in the presence of tetrabutylamonium fluoride (TSB series) or aqueous HCI (MEB and ETB series), resulting in PS containing carbonyls inserted in its backbone. The polymers were isolated and characterized by infrared spectroscopy (IR), elemental analysis, size exclusion chromatography (SEC), time dependent static light scattering (TDSLS), thermal analysis (TG and DSC) and scanning electron microscopy (SEM). The polymeric solutions were irradiated with a low pressure mercury lamp (99.5% emission at 254 nm), in the presence of air at room temperature, for a period of 10 hours. The polymer changes were followed by IR, TDSLS and SEC. The infrared spectra showed a continuous increase in the intensity of some bands: the broad band in the region of 3800 - 3000 cm-1 was assigned to the formation of hydroxides or hydroperoxides groups; the band at 1900 - 1500 cm-1 with a shoulder at 1712 cm-1 can be assigned to ketones or aldehydes, which appear as chain termination groups and the band at 1500 - 1000 cm-1 was attributed to the formation of anhydrides. The TDSLS studies clearly showed that the copolymers degradated much faster than the pure PS, and the degradation rates were directly related to the increase in the TSB, MEB and ETB contents of the polymer. This observation is supported by the decreasing molecular weight values obtained by SEC (Mw) for the resulting fragments from photolysis, when the carbonylic content of the polymer increased, starting at around 34.0 kg/mol (TSB5), for instance, decreasing to Mw values as low as 4.8 kg/mol (TSB15). Finally, we tried to found out the polymer behavior when exposed to the real outdoor conditions of use, by submitting samples to an accelerated aging process in a Weather-o-Meter chamber and evaluating its mechanical behavior afterwards. The results showed that for both, homo and copolymers, there was a reduction in the tensile strength with increasing in the exposition time (0 to 600 hours). This behavior is much stronger in the copolymers.

Este trabalho é direcionado ao estudo dos efeitos da radiação UV sobre amostras de poliestireno (PS) e de copolímeros de estireno com proporções variáveis de 2-trimetilsililóxi-1,3-butadieno (TSB, I), 2-metóxi-1,3-butadieno (MEB, II) e 2-etóxi-1,3-butadieno (ETB, III), em solução aerada, visando principalmente à amplificação da degradação ambiental do PS quando exposto a condições de intemperismo natural. (Ver no arquivo em PDF). Os polímeros foram sintetizados via polimerização radicalar em solução, resultando em uma massa molar ponderai média (Mw) de cerca de 30,0 kg/mol para o homo e copolímeros. Estes produtos, após serem submetidos a um processo de hidrólise na presença de fluoreto de tetrabutilamônio (série TSB) ou HCI aquoso (séries MEB e ETB), resultaram em PS contendo grupos carbonila na cadeia principal sendo, a seguir, isolados e caracterizados por meio de técnicas analíticas como espectroscopia de infravermelho (IR), análise elementar, cromatografia de exclusão por tamanho (SEC), espalhamento de luz estático dependente do tempo (TDSLS), análise térmica (TG e DSC) e microscopia eletrônica de varredura (MEV). As soluções poliméricas foram irradiadas com lâmpada de mercúrio de baixa pressão (99,5% de emissão a 254 nm), na presença de ar e à temperatura ambiente, por um período de dez horas. As alterações sofridas pelos polímeros foram acompanhadas por meio de medidas de IR, TDSLS e SEC. Os espectros no infravermelho mostraram um aumento contínuo da intensidade de algumas bandas: na região entre 3800 - 3000 cm-1, houve um alargamento das bandas que pode ser atribuído à formação de grupos hidroxila e/ou hidroperóxido; na região de 1900 - 1500 cm-1, observou-se o aparecimento de um ombro em 1712 cm-1, que pode ser atribuído à formação de grupos cetona e aldeído como funções terminais na cadeia do polímero e, na região entre 1500 - 1000 cm-1, o alargamento das bandas foi atribuído à formação de grupos anidrido. Os estudos realizados por TDSLS revelaram claramente que os copolímeros degradam com mais rapidez que o PS puro, e as taxas de degradação aumentam proporcionalmente ao aumento no teor de carbonilas incorporadas ao polímero. Tal observação tem suporte nas massas molares ponderais médias obtidas via SEC (Mw) dos fragmentos resultantes da fotólise, com valores cada vez menores com o aumento dos efeitos da fotodegradação, iniciando com cerca de 34,0 kg/mol (TSB5), por exemplo, e decrescendo a valores de Mw tão baixos quanto 4,8 kg/mol (TSB15). Para finalizar, tentou-se verificar o comportamento dos polímeros quando expostos a condições reais de utilização, submetendo-se corpos de prova a um envelhecimento acelerado em câmara de intemperismo artificial e avaliando seu comportamento mecânico. Os resultados mostraram que, para homo e copolímeros, houve uma redução na resistência à tração com o aumento do tempo de exposição (0 a 600 horas), sendo este efeito muito mais acentuado para os copolímeros. / This work was directed to the study of the UV radiation effects upon samples of polystyrene (PS) and copolymers of styrene with different fractions of 2-trimethylsililoxy-1,3-butadiene (TSB, I), 2-methoxy-1 ,3-butadiene (MEB, II) and 2-ethoxy-1,3-butadiene (ETB, III), in normally aerated solution, aiming at the optimization of the PS degradation when exposed to weathering conditions. (See in the PDF file). The polymers were prepared by free-radical polymerization in solution, resulting in average molecular weight (Mw) of about 30.0 kg/mol for the homo and copolymers. The resulting polymers were submitted to hydrolysis in the presence of tetrabutylamonium fluoride (TSB series) or aqueous HCI (MEB and ETB series), resulting in PS containing carbonyls inserted in its backbone. The polymers were isolated and characterized by infrared spectroscopy (IR), elemental analysis, size exclusion chromatography (SEC), time dependent static light scattering (TDSLS), thermal analysis (TG and DSC) and scanning electron microscopy (SEM). The polymeric solutions were irradiated with a low pressure mercury lamp (99.5% emission at 254 nm), in the presence of air at room temperature, for a period of 10 hours. The polymer changes were followed by IR, TDSLS and SEC. The infrared spectra showed a continuous increase in the intensity of some bands: the broad band in the region of 3800 - 3000 cm-1 was assigned to the formation of hydroxides or hydroperoxides groups; the band at 1900 - 1500 cm-1 with a shoulder at 1712 cm-1 can be assigned to ketones or aldehydes, which appear as chain termination groups and the band at 1500 - 1000 cm-1 was attributed to the formation of anhydrides. The TDSLS studies clearly showed that the copolymers degradated much faster than the pure PS, and the degradation rates were directly related to the increase in the TSB, MEB and ETB contents of the polymer. This observation is supported by the decreasing molecular weight values obtained by SEC (Mw) for the resulting fragments from photolysis, when the carbonylic content of the polymer increased, starting at around 34.0 kg/mol (TSB5), for instance, decreasing to Mw values as low as 4.8 kg/mol (TSB15). Finally, we tried to found out the polymer behavior when exposed to the real outdoor conditions of use, by submitting samples to an accelerated aging process in a Weather-o-Meter chamber and evaluating its mechanical behavior afterwards. The results showed that for both, homo and copolymers, there was a reduction in the tensile strength with increasing in the exposition time (0 to 600 hours). This behavior is much stronger in the copolymers.

Ultravioletiniai spinduliai veikia daugelį polimerų, tame tarpe ir polipropileną. Darbo tikslas buvo ištirti ultravioletinės spinduliuotės (=254 nm) poveikį polipropilenui. Medžiagos cheminės sudėties pokyčiui nustatyti buvo matuojami infraraudonųjų spindulių absorbcijos spektrai, o fizinių savybių pokytis – matuojant stiprumo ribą, regimosios šviesos praleidimo faktorių, induktyvumą bei kontūro elektrinę talpą. Nustatyta, kad polipropileną veikiant 254 nm bangos ilgio šviesa medžiaga palaipsniui oksiduojasi. UV spinduliuotė generuoja peroksidinių (>CH-O-OH), karbonilinių (>C=O) ir vinilinių (-CH=CH2) grupių susidarymą anglies grandinėse ir jų koncentracija didėja ilginant švitinimo trukmę. Po 160 val. švitinimo prasideda polimero degradacija: keičiasi jo struktūra, prarandamas skaidrumas, elastingumas, didėja trapumas bei mažėja polipropileno plėvelės storis. Polipropileno paviršiuje atsiranda įtrūkimų, plėvelė pageltonuoja. Magnetinių savybių matavimai rodo, kad oksiduojantis polipropilenui didėja laisvųjų radikalų koncentracija propileno grandinėse. Mikroskopiniai tyrimai parodė plėvelės paviršiuje susidariusias destrukcijos juostas. / Wide verily of polymers undergo physicochemical changes. The aim of the paper was to study the effect of ultraviolet radiation (λ= 254 nm) on polypropylene. The chemical changes were measured by the infrared absorption spectra, and the change the physical properties – by measurement of the strength limit, visible light transmittance, polypropilene inductance and capacitance. It is determined that PP exposed to ultraviolet light undergo photo-oxidation and photo-degradation. UV radiation generates formation of peroxide (>CH-O-OH), carbonyl (>C=O) and vinyl (-CH=CH2) groups in the carbon chaines with increasing their concentrations during exposure. After 160 hours UV exposure process of PP destruction gets up: the transparency, elasticity, polypropilene film thickness and strenght is declining. Microscopic demonstrated the cracks on the surface of the films after 160 hours of exposure.

Over the past two decades a body of evidence concerning residual biological contamination on cleaned surgical instruments has accumulated. This is substantiated by the number of yearly surgery cancellations due to visible residue on instruments in surgical packs and incidences of iatrogenic Creutzfeldt-Jakob disease (iCJD). It is therefore imperative to develop a method of protein detection for use in clinical sterile services departments (SSDs) for monitoring of decontamination quality. This Thesis describes the development and use of an epifluorescence surface scanner (EFScan) technology in the assessment of proteinaceous residue on surgical instruments, by detecting protein pre-labelled with fluorescein isothiocyanate (FITC), and exploratory studies on the feasibility of label-free detection, using intrinsic protein fluorescence. Measurements using FITC labelling showed that residual protein on the order of micrograms can be found on new, single-use instruments (i.e. prior to use). This is comparable to the amount of residual protein found on retired, reusable instruments. To confirm the suitability of fluorescence techniques in the detection and quantification of proteinaceous residue, a blind, pilot study was carried out in conjunction with groups from Queen Mary University and the University of Southampton. Each University used a different labelling and detection method, and results showed good agreement between these methods. This showed that fluorescence is a suitable technique for the detection and quantification of proteinaceous contamination on surgical instruments. The next step in the project focussed on detection of contamination via intrinsic protein fluorescence from tryptophan residues, with a view to elimination of the labelling step. Intrinsic fluorescence of proteins in solution is widely characterised; however, fluorescence characteristics of solid or surface-bound protein have been little studied. Therefore, the characterisation of solid protein fluorescence and the emission characteristics of protein adsorbed onto stainless steel was undertaken. Analysis of the commonly used protein standard bovine serum albumin (BSA) showed that the two tryptophan residues it contains are highly susceptible to photo-oxidation in the solid state, resulting in conversion to the fluorescent photoproducts n-formylkynurenine (NFK) and kynurenine. Therefore, BSA is not suitable for use as a standard in the development of intrinsic fluorescence detection of surface-bound protein. The 72-tryptophan protein fibrinogen, as well as a series of other multi-tryptophan proteins, were assessed and it was found that photo-oxidation of the tryptophan residues did not occur on the irradiation timescale of 1 hour utilized. Therefore, it was concluded that lysozyme or gamma-globulins, a prominent group of serum proteins, would be more suitable candidates as a standard in subsequent research into the intrinsic detection and quantification of proteinaceous contamination. A third study explored the potential use of fluorescence in the early diagnosis of cataract. This involved the fluorescence characterisation of healthy porcine lenses and the use of UV irradiation of the lens to attempt to create cataract in vitro. There was found to be a large variation in fluorescence characteristics from lens to lens, suggesting that fluorophore concentrations can vary significantly. This implies that identification of a suitable standard for the early detection of cataract may be problematic. Attempts to create cataract resulted in the photo-oxidation pathway which had been observed in BSA, and although NFK and kynurenine play a role in cataractogenesis, the accumulation of these photoproducts is not analogous to a natural cataract. It was found that these products could be destroyed by irradiation of the lens at appropriate photo-bleaching wavelengths. However, this also destroyed intrinsic, protective fluorophores within the lens, suggesting that a light-based method of cataract treatment may not be achievable.

No description available.