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The thermo-oxidative degradation of unstabilized polyamide 6 (PA-6) was investigated by a number of novel techniques in an attempt to achieve a better understanding of the mechanisms involved in the oxidative degradation of polymers. Particular attention was given to the influence of end groups on PA-6 oxidation by studying samples that terminated predominantly in carboxylic, amine or methyl end groups. The changes occurring in the oxidative stabilities and mechanisms of PA-6 as a result of altering the end groups of PA-6 were investigated by a technique termed CL-DSC, which simultaneously measures the chemiluminescence (CL) and heat flow (DSC) from a sample. When amine end groups were abundant in the PA-6 sample a chemically induced electron exchange luminescence (CIEEL) mechanism could occur directly and the CL intensity was proportional to the heat flow curve of the DSC. However, when amine end groups were absent it was the first derivative of the CL intensity that was proportional to the heat flow curve because the CIEEL mechanism could not operate until an easily oxidisable luminescent oxidation product was formed. Due to the dramatic effect end groups have on the oxidation mechanisms of PA-6 it was hypothesized that end groups could be sites analogous to the impurities in polyolefins that lead to heterogeneous oxidation. To test this hypothesis, CL Imaging was used to map the occurrence and extent of oxidation across samples of PA-6 to display the influence end groups have on the homogeneous or heterogeneous nature of PA-6 oxidation. Sequences of FTIES spectra collected at specified time intervals during the in situ oxidation of PA-6 samples terminating in the different end groups were turned into oxidation product profiles. The differences between spectra related to significant points on the oxidation profiles were compared in an attempt to elucidate the chemical or physical changes occurring in the samples during oxidation. To identify the species involved in the mechanistically different oxidation processes resulting from the different end groups, methods for the MALDI-TOF analysis of non-oxidized and oxidized PA- 6 samples were developed via trial and error. It was only possible to detect the occurrence of degradation products by MALDI-TOF MS after considerable oxidation as measured by chemiluminescence, by which time the species were the result of a number of oxidative processes. Therefore, identification of the species formed was not possible.

Carbon fiber (CF) 8-harness satin weave, T650/Neximid system of [(+45/-45)/(0/90)]2S and [(0/90)]4S layup was manufactured using resin transfer molding (RTM). The material was cut into 3-point bending specimens and treated for 24 hours in a burn oven at T=(320,350,375,400,450 & 500)°C. The material was tested according to ASTM E1640-13 using dynamic mechanical thermal analysis (DMTA). Un-treated material showed Tg levels of 384°C and 392°C for the respective layups. It was found that pre-Tg treatment between 320-375°C affected this material parameter up to similar levels as previous studies of post Tg exposure for 2h to ~420°C [4]. Subjecting the material for post-Tg exposure at 400°C showed a rapid change up to ~480°C for [(0/90)]4S laminate. Indications that this resin system could reach levels above 500°C was found for [(+45/-45)/(0/90)]2S layup. However, one of these specimens were unfit for testing. DMTA tested material for 400°C showed indications of degradation, found by a broadening of the tan delta peak. This can be put in relation to epoxy where a similar behavior appear after 24h exposure at 150°C. Furthermore, it was showed that poor quality laminate, elevated mass loss at this temperature. When the material was subjected to as high temperatures as 450°C only remaining fibers were found. At 500°C these were almost fully oxidized. 400°C data was predicted by the use of activation energy along with TG extrapolation. It was possible to show that ~1/8 out of this 8-layered structure, (½ of each surface layer), was degraded after 400°C exposure for 24h, resulting in diffusion limited oxidation (DLO). Last but not least, DLO assumptions was used to predict the storage modulus change for thermo-oxidative degradation of 400°C samples with Classic Laminate Theory (CLT). A ~4% stiffness decrease was predicted by this method. The drop is regarded as a loss in tensile stiffness of the outer damaged layer. This was compared by 3-point bending DMTA data showing a ~7% decrease. This model could thus be regarded as a contributing factor for the stiffness decrease of this complex degradation process. / Kolfiber, 8-harness satin väv, T650/NEXIMID system med [(+45/-45)/(0/90)]2S och [(0/90)]4S orientering, tillverkades via RTM. Från materialet tillverkades 3-punkts böjprover. Dessa behandlades i 24 timmar vid T=(320, 350, 375, 400, 450 & 500)°C, i en brännugn. Materialet testades i enighet med ASTM E1640-13 via DMTA. Obehandlat material visade Tg nivåer av 384°C och 392°C för de respektive uppläggningarna. Pre-Tg exponering, vid 320-375°C, påverkade Tg upp till liknande nivåer som tidigare studier, (post-Tg 2h), ~420°C [4]. När materialet utsätts för post Tg exponering under 24 timmar vid 400°C kunde man se en snabb förändring av Tg, upp till ~480°C för [(0/90)]4S laminatet. Från [(+45/-45)/(0/90)]2S laminatet kunde man dessutom se indikationer på att nivån kunde nå över 500°C. Däremot var en av dessa prov inte kvalificerad för test efter behandlingen. DMTA testat material för 400°C visade indikationer av nedbrytning, via en breddning av piken för tan-delta kurvan. Det var dessutom möjligt att se att laminat av sämre kvalitet påverkade viktminskningen signifikant högre vid denna exponering. När material utsattes för så höga temperaturer som 450°C var endas fiber kvar efter test, vilket vid 500°C nästan var fullt nedbrutna. 400°C data förutspåddes via extrapolering av TG och Arrhenius beräkning. Beräkningen ledde till en övre gräns för nedbrytningen. Vidare var det möjligt att visa att ~1/8 av dessa 8-lager bröts ner efter 24 timmars exponering vid 400°C. Nedbrytningen motsvarar ½ av vartdera ytlager via diffusions begränsad oxidation (DLO). Sist men inte minst, kunskapen om DLO användes för att förutspå styvhetsförändringen vid termo-oxiderande nedbrytning med hjälp av klassisk laminat teori (CLT). DLO antogs resultera i en volymfraktionsförändring i det yttersta lagret. Detta implementerades i CLT där man kunde beräkna en ~4% styvhetsminskning via denna modell där det yttre skadade lagret har en reducerad dragstyvhet. Från testade böjprover i DMTA kunde man se en verklig ~7% styvhetsminskning för samma exponeringsvillkor. Modellen kan därmed ses som en bidragande del av denna komplexa nedbrytningsprocess.

Extended Hückel methods are known to be a useful tool in understanding surface phenomena. Important quantities about atoms and chemical bonds can be obtained from this computationally simple method, although caution must be exercised in interpreting the results. Application of Extended Hückel calculations to large metal clusters reveals the role of d orbitals in solids. Basic ideas of constructing model compounds have been developed. Several model systems for surface chemisorption processes are constructed in order to understand the surface catalyzed oxidative degradation of polyperfluoroethers. The activation of oxygen molecules can be explained. The Lewis acid character of the iron fluoride surface can be predicted. Based on these results, mechanisms of the degradation processes are discussed.

"Modeling and Simulation of Oxidative Degradation of UHMWPE is studied in details.UHMWPE is commonly used in knee replacements or total hip replacements."

Today, a majority of the world’s energy need is supplied through sources that are finite and, at the current usage rates, will be consumed shortly. The high energy demand and pollution problems caused by the widespread use of fossil fuels make it increasingly necessary to develop renewable energy sources of limitless duration with smaller environmental impact than the traditional energy sources. Three fuels – rapeseed methyl ester (RME), Fischer-Tropsch (FT) diesel and FT jet fuel – derived from biomass, coal or gas were evaluated in this project. The fuel properties evaluated are in most cases listed in standards, often with recommendations, developed for biodiesel, petroleum diesel and jet fuel. Biodiesel is monoalkyl esters, e.g. RME, produced by transesterification of triglycerides in vegetable oil and an alcohol to esters and glycerin. This produce a fuel that is suitable as a direct substitution for petroleum diesel. Biodiesel may be used in pure form or in a blend with petrodiesel. Oxidative degradation and weak low temperature performance of biodiesel are properties of concern when substituting petrodiesel with biodiesel, as was shown in this project. The experiments show that oxidative stability can be improved with a synthetic antioxidant, e.g. butylated hydroxytoluene (BHT). The FT process converts syngas (a mixture of hydrogen and carbon monoxide) to a range of hydrocarbons. Syngas can be generated from a variety of carbon sources, e.g. coal, natural gas and biomass. The high-temperature (300-350 °C) FT process with iron-based catalysts is used for the production of gasoline and linear low molecular mass olefins (alkenes). The lowtemperature (200-240 °C) FT process with either iron or cobalt catalysts is used for the production of high molecular mass linear waxes. By applying various downstream processes, fuels suitable for substitution of petrodiesel and conventional jet fuel can be obtained. The FT fuels have lower densities than the conventional fuels. However, conclusions from this project are that most of the properties of FT fuels are better, or equal, than conventional petroleum fuels.

ABSTRACT PHOTO-OXIDATIVE DEGRADATION OF ABS COPOLYMER G&uuml / zel, Aylin M.S., Department of Polymer Science and Technology Supervisor: Prof. Dr. Teoman Tin&ccedil / er Co-Supervisor: Prof. Dr. Cevdet Kaynak September 2009, 55 pages Acrylonitrile-butadiene-styrene (ABS) polymer is one of the most popular copolymer having an elastomeric butadiene phase dispersed in rigid amorphous styrene and semi-crystalline acrylonitrile. Due to double bonds in the polybutadiene phase, ABS copolymers are very sensitive to photo-oxidative degradation. Photo-oxidation of butadiene rubber phase results in the formation of chromorphores and these chromorphores act as initiators in photo-oxidative degradation and after a while ABS starts yellowing. In this work, the relationship between the UV light and the yellowing of ABS samples was also investigated with respect to time. In this study, pure, light stabilized and commercial ABS samples were aged under UV light. As the UV light intensity increased from 800 to 2800 &amp / #61549 / W/cm2, yellowing of the samples were increased for pure ABS. This increase in yellowing of the samples was about 27 times higher compared to lower energy. In this study, UV stabilizers IRGANOX 1076 (sterically hindered phenolic antioxidant), IRGAFOS 168 (hydrolycally stable phosphite stabilizer) and TINUVIN P (hydroxyphenol benzotriazole) were used alone or in combination with each other. Pure ABS samples, commercial ABS samples and UV stabilized ABS samples were aged under the same UV light. UV aging degradation was followed by measuring the yellowness of the samples at certain time intervals. Yellowness of the samples was followed by using Coloreye XTH Spectrometer. Degradation in ABS, however, was followed by using FTIR with an increase in the peak area of carbonyl groups in the ABS matrix. Both color analysis and the FTIR analysis showed that combination of the IRGANOX 1076 and IRGAFOS 168 stabilizers gave the best stabilization. This revealed that combination of phenol and phosphate containing stabilizer is the most useful combination to prevent photo-oxidative degradation of ABS copolymer. Additionally, vegetable oil was applied to the surface of a new set of ABS samples and these samples were aged for 700 h. Yellowing tendency of these samples was compared with the yellowing tendency of ABS samples that are directly aged for 500 h. It was clearly observed that samples with oil smeared had more resistance to UV radiation with respect to others. This shows that oil acts protective layer to the UV light and oxygen and slow down the photo-oxidative degradation. Lastly some commercial ABS samples were compared to each other with respect to their yellowing tendency. Commercial ABS samples coded as K, L, A, B, C and D were aged under UV light at about 500 h. Sample A showed the best resistance against the yellowing among the other commercial ABS samples.

<p>Today, a majority of the world’s energy need is supplied through sources that are finite and, at the current usage rates, will be consumed shortly. The high energy demand and pollution problems caused by the widespread use of fossil fuels make it increasingly necessary to develop renewable energy sources of limitless duration with smaller environmental impact than the traditional energy sources.</p><p>Three fuels – rapeseed methyl ester (RME), Fischer-Tropsch (FT) diesel and FT jet fuel – derived from biomass, coal or gas were evaluated in this project. The fuel properties evaluated are in most cases listed in standards, often with recommendations, developed for biodiesel, petroleum diesel and jet fuel.</p><p>Biodiesel is monoalkyl esters, e.g. RME, produced by transesterification of triglycerides in vegetable oil and an alcohol to esters and glycerin. This produce a fuel that is suitable as a direct substitution for petroleum diesel. Biodiesel may be used in pure form or in a blend with petrodiesel. Oxidative degradation and weak low temperature performance of biodiesel are properties of concern when substituting petrodiesel with biodiesel, as was shown in this project. The experiments show that oxidative stability can be improved with a synthetic antioxidant, e.g. butylated hydroxytoluene (BHT).</p><p>The FT process converts syngas (a mixture of hydrogen and carbon monoxide) to a range of hydrocarbons. Syngas can be generated from a variety of carbon sources, e.g. coal, natural gas and biomass. The high-temperature (300-350 °C) FT process with iron-based catalysts is used for the production of gasoline and linear low molecular mass olefins (alkenes). The lowtemperature (200-240 °C) FT process with either iron or cobalt catalysts is used for the production of high molecular mass linear waxes. By applying various downstream processes, fuels suitable for substitution of petrodiesel and conventional jet fuel can be obtained. The FT fuels have lower densities than the conventional fuels. However, conclusions from this project are that most of the properties of FT fuels are better, or equal, than conventional petroleum fuels.</p>

Compósitos de Poli (óxido de etileno) (PEO) com diferentes concentrações de argila montmorilonita SWy-1 foram preparados pelo método de intercalação em solução. Os filmes obtidos foram caracterizados por difração de raios X (DRX), microscopia eletrônica de varredura (MEV) e espectrocopia de infravermelho com transformada de Fourier (FTIR). Os resultados de DRX mostraram que os compósitos obtidos foram do tipo intercalados. As imagens de MEV indicaram a existência de agregados de argila SWy-1 dispersos na matriz polimérica. A influência da argila na estabilidade térmica e na cristalização do PEO foi estudada por termogravimetria (TG) e calorimetria exploratória diferencial (DSC). As curvas TG mostraram que a temperatura inicial de degradação térmica (Ti) diminui com o aumento da concentração de SWy-1. Além disso, uma pequena diminuição na amplitude do pico de fusão do PEO foi observado nos resultados de DSC. Os filmes de PEO e dos compósitos de PEO/SWy-1 foram irradiados com luz UV e a fotooxidação foi acompanhada por cromatografia de exclusão por tamanho (SEC). Os resultados de SEC mostraram que a taxa de oxidação do PEO puro foi mais rápida em comparação aos compósitos de PEO/SWy-1. Nesse caso a argila pode ser considerada como um estabilizante contra a irradiação UV. O efeito de estabilizantes do tipo absorverdores de UV (moléculas derivadas da 2-hidroxibenzofenona) e do tipo HALS (Tinuvin 770), quando adicionados ao PEO e ao compósito de PEO/SWy-1, também foi analisado por SEC após a fotooxidação dos filmes. Os resultados mostraram que a adição do estabilizante Tinuvin 770 proporcionou maior estabilidade a matriz polimérica durante o processo degradativo, comparado ao estabilizante 2-hidroxibenzofenona. / Poly(ethylene oxide) (PEO) composites with different concentrations of SWy-1 montmorillonite clay were prepared by solution intercalation method. The thin films obtained were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The XRD results showed that the composites obtained were of the type intercalated. The SEM images have indicated that there are SWy-1 clay aggregates scattered in the polymer matrix. The influence of clay on thermal stability, melting and polymer crystallization processes was studied by thermogravimetric analysis (TG) and differential scanning calorimetric (DSC). The TG curves showed that the initial thermal degradation temperature (Ti) decrease with increasing concentration of SWy-1. Besides, a small decrease in the amplitude of the melting peak of PEO was observed in the DSC results. The thin films of PEO and PEO/SWy-1 composites were exposed to UV irradiation and the photodegradation was accompanied by size exclusion chromatography (SEC). The SEC results showed that the rate of oxidation of pristine PEO was faster compared to PEO/SWy-1 composites. In this case the clay can be considered as a stabilizer against UV irradiation. The effect of UV absorbers (2-hydroxybenzophenone derivated molecules) and HALS (Tinuvin 770) stabilizers, when added to PEO and PEP/SWy-1 composites, also were studied by SEC after the thin films photodegradation. The results allowed to conclude that the polymer matrix became more stable for degradation with adition of Tinuvin 770 stabilizer when compared to 2-hydroxybenzophenone.

No contexto em que vivemos é crescente a necessidade de reciclar materiais, principalmente, devido a questões que envolvam a redução dos impactos ambientais, como, por exemplo, a reciclagem de materiais para fabricação de produtos tecnológicos. Equipamentos eletroeletrônicos possuem grande potencial para reciclagem e são descartados diariamente. A degradação por foto-oxidação é um fator que pode influenciar nas propriedades dos polímeros que compõe um equipamento eletroeletrônico, e em sua reciclagem, mesmo em ambientes internos, pois o UVA tem capacidade de transpor janelas de vidro. Este estudo analisou alguns aspectos da foto-oxidação do poliestireno de alto impacto (PS-HI) reciclado de carcaças de impressoras, exposto à radiação UVA com base nas normas de envelhecimento ASTM G24 e G154. Amostras de PS-HI virgem e reciclado foram injetadas e expostas ao envelhecimento acelerado em laboratório por meio de grades, com a exposição total das amostras, e em máscara, com o direcionamento da radiação UVA em ponto determinado das amostras. As consequências da foto-oxidação nas propriedades das amostras foram caracterizadas por: Colorimetria, Espectroscopia de Infravermelho, Microscopia Eletrônica de Varredura e Análise Térmica Dinâmico Mecânico, com o objetivo de avaliar a degradação foto-oxidativa do poliestireno de alto impacto reciclado e caracterizar e as diferenças entre a exposição total e direcionada. Os resultados apontaram que as amostras recicladas expostas a radiação UVA não apresentaram mudanças consideráveis em relação as suas propriedades ou processabilidade quando comparado com o material virgem, pois a foto-oxidação ficou concentrada na superfície das amostras. / In today’s context it is increasingly necessary to recycle materials, such as the ones used in the manufacturing of technological products, mainly due to issues involving the reduction of environmental impact. Electronic devices are discarded daily and they have a great potential for recycling. Degradation by photo-oxidation is a factor that can influence the properties and the recycling of polymers that make up pieces of electronic equipment. This factor exists even indoors, because UVA is able to travel across glass windows. This study analyzes some aspects of the photo-oxidation of high impact polystyrene (HIPS) recycled from printer carcasses that were exposed to UVA under the ASTM G24 and G154 aging standards. Virgin and recycled HIPS samples were injected and exposed to an accelerated aging process in the laboratory through the use of pallets, with the total exposure of the samples, and masks with the targeted UVA exposure at certain points of the samples. The consequences of the photo-oxidation on the properties of the samples were characterized by: colorimetry, infrared spectroscopy, scanning electron microscopy and Dynamic Mechanical Thermal Analysis with the objectives of evaluating the degradation of recycled HIPS caused by photo-oxidation and characterizing the differences between pallet and mask exposure. The results showed that when compared to the virgin material, the recycled samples that were exposed to UVA radiation did not undergo significant changes regarding the properties and processability because the photo-oxidation effect remained focused on the areas near the surface of the samples.