Thesis--Universität-Gesamthochschule-Paderborn.

Plastics play an enormous role in modern manufacturing, but the extraction and refining of raw materials, followed by the synthesis of plastics themselves, represents an enormous energy investment into a product that is all too often simply “thrown away” into a landfill after a single use. Microwave-assisted pyrolysis is a recycling technique that allows the recovery of chemical value from plastic waste by breaking down polymers into useful smaller hydrocarbons using microwave heat in the absence of oxygen. This dissertation examines the use of a catalytic activated carbon bed in this procedure, using high density polyethylene (HDPE) as a model plastic. Initial tests with the batch input of HDPE produced a condensed pyrolysis oil comprising 35.5–45.3% aromatics, with the remainder primarily short-chain aliphatics. This oil was approximately three times lighter than that produced in the absence of catalyst, with a narrower range of molecular masses that matched those of the liquid transport fuels petrol and diesel (C5–C21). The non-condensable gases that resulted were short-chain aliphatics that could be used as feedstock for the creation of new chemicals (such as virgin HDPE), or fuels such as natural gas and LPG. The development of apparatus capable of adding sample in a continuous fashion enabled the processing of larger quantities of HDPE, and resulted in condensed products with a significantly higher aromatic content (>80% at 450°C), and which encompassed a somewhat narrower range of molecular masses compared with those produced in the batch mode; this was due to differences in kinetics and residence time that resulted from the different modes of sample introduction. As a result of processing larger quantities of HDPE it became apparent that the activated carbon deactivated over time, with a bed able to process around 3.5 times its mass in HDPE at 450°C before any significant changes in output products occurred. The decomposition of HDPE proceeds via thermal scission and radical-mediated mechanisms; high energy surface active sites facilitate the transfer of hydrogen and radicals, and this enhances overall cracking and lowers the activation energy for the formation of aromatics. Analysis of material deposited on the surface of the activated carbon confirmed that deactivation occurred through coking, with both cracking and deactivation thought to be enhanced by the formation of microwave-induced microplasmas. Overall, the microwave-assisted pyrolysis of HDPE using activated carbon produces a much narrower range of more valuable products compared with non-catalytic processing. While the process is not likely to be economic in its current form owing to the relatively rapid deactivation of the activated carbon, future configurations incorporating online reactivation may be able to economically provide a second use cycle for these materials, avoiding expending energy to extract and process increasingly scarce new raw material from the surface of the earth.

This thesis deals with the relation between structure and resistance to failure by the mechanism of slow crack growth (SCG) in HDPE. In the theoretical part there are summarized previously acquired knowledge about the production of PE and about the relation between structure and resistance to failure by the SCG mechanism. In the experimental part, three samples of HDPE with the same melt index MI and the same content of copolymer 1- hexene were synthesized by using three chromium catalysts commonly used for polymerization in industry. There samples were analyzed by GPC-IR-MALS and TREF in order to determine the distribution of side chain branches. The results were discussed with respect to the time to failure FNCT.

Campylobacter spp. are the second leading bacterial cause of food borne illness in the U.S.  New antimicrobials that prevent bacterial attachment may be effective for reducing Campylobacter.  Delmopinol hydrochloride (delmopinol) is a cationic surfactant that is effective for treating and preventing gingivitis and periodontitis.  This study evaluated the effectiveness of delmopinol for reducing attachment of Campylobacter jejuni to chicken, stainless steel and high-density polyethylene. Chicken pieces, steel and HDPE coupons were spot-inoculated with 0.1 mL of a Campylobacter jejuni culture.  After 10 min, samples were sprayed with 0.5% or 1.0% delmopinol, 0.01% sodium hypochlorite, or distilled water.  Contact times were 1, 10, or 20 min prior to rinsing with buffered peptone water. Rinses were serially diluted onto Campy Cefex Agar for enumeration.  For additional samples, solutions were applied first, followed by inoculation with C. jejuni after 10 min.  Cultures remained undisturbed for 1, 10, or 20 min.  Then samples were rinsed and plated as above. When C. jejuni was inoculated before treatments, 1% delmopinol application led to mean log reductions of 1.26, 3.70, and 3.72 log CFU/mL, greater than distilled water, for chicken, steel and HDPE respectively. When C. jejuni was inoculated after spray treatments, 1% delmopinol reduced C. jejuni by 2.72, 3.20, and 3.99 mean log CFU/mL more than distilled water for chicken, steel and HDPE respectively.  Application of 1% delmopinol, either before or after bacteria inoculation, resulted in a significantly (p<0.05) greater log reduction than 0.01% sodium hypochlorite or distilled water. Delmopinol may be a promising antimicrobial treatment. / Master of Science in Life Sciences

Överums Bruk AB tillverkar jordbruksmaskiner såsom konstgödselrampspridaren Wing Jet. Wing Jet har idag en konstgödselbehållare tillverkad i rostfritt stål och företaget önskar veta om det är möjligt och lämpligt att tillverka behållaren i plast/plastkomposit i syfte att minska produktionskostnaden av behållaren samt dess vikt. Detta arbete är begränsat till behållaren, övriga konstgödselspridaren ska inte behöva några förändringar för att byta den rostfria behållaren till en i plast/plastkomposit och det ingår inte i arbetet att tillverka en prototyp. Rotationsgjutning och handuppläggningsmetoden (glasfiberarmering) är två tillverkningsmetoder som är lämpliga att använda vid tillverkning av så stora objekt. Simuleringar av en rotationsgjuten behållare i materialet högdensitetspolyeten (HDPE) i programmet SolidWorks Simulation Standard resulterar i maximala effektivspänningar strax över materialets brottgräns då ett tryck baserat på ekvationer från europastandarden Eurocode 1-4: 2006 (Silor) anläggs på behållarens insida. Det uppstår dock deformationer på flera centimeter vilket i sig inte är ett problem, men det gör behållaren mindre estetiskt tilltalande (släta sidor buktar utåt). Behållarens vikt minskar till ca hälften av dagens och den är billigare att tillverka. Material och tillverkningsmetoder som resulterar i en behållare med högre styvhet i avseende att minska deformationen är rekommenderat att undersökas som vidare arbete. Exempel på detta är glasfiberarmerad polyester eller epoxi och ”sandwich”-konstruktioner. En sandwich-konstruktion består av två (eller fler) lager av ett material med en kärna, av t.ex. ett skum, mellan. Genomförda simuleringar är linjärelastiska, medan plaster allmänt är olinjära, så olinjära simuleringar bör genomföras innan prototyp tillverkas. / Överums Bruk AB manufactures agricultural equipment such as the fertilizer spreader Wing Jet. Wing Jet has a container which today is manufactured from stainless steel and the company wishes to know if it is possible and suitable to manufacture the container from plastic/plastic composite with the purpose to lessen the containers production costs and weight. This work is limited to the container, the rest of the fertilizer spreader should not need any changes to switch the stainless steel container for a plastic/plastic composite one and the work does not include manufacturing a prototype. Rotational molding and hand lay-up (glass-fibre reinforcement) are two manufacturing processes which are suitable to use when manufacturing such large objects. Simulations of a rotational molded container in the material high density polyethylene (HDPE) in the program SolidWorks Simulation Standard results in maximum effective stresses just above the materials tensile strength when a pressure based on equations from the European standard Eurocode 1-4: 2006 (Silos and Tanks) are applied on the containers inside. However, deformations of several centimeters occurs which in itself is not a problem, though it makes the container less esthetically appealing (smooth sides bulges outward). The containers weight decreases to approximately half of that of today and it is cheaper to manufacture. Materials and manufacturing processes which results in a container with higher stiffness in the purpose of lessen the deformation is recommended to investigate as future work. Examples of this are glass-fibre reinforced polyester or epoxy and “sandwich”-constructions. A sandwich-construction is comprised of two (or more) layers of a material with a core, of e.g. foam, between. The simulations carried out are linear elastic, whereas plastics generally are non-linear, so non-linear simulations should be carried out before a prototype in manufactured.

Techn. Universiẗat, Diss., 2003--Braunschweig.

No description available.

Depuis quelques années, les polyoléfines et en particulier le Polyéthylène présentent un intérêt économique qui se traduit par un marché en croissance constante. Cependant, il est souvent nécessaire d’améliorer leurs propriétés d’usage notamment pour des problématiques liées à l’industrie automobile. Dans ce contexte, une amélioration des propriétés thermomécaniques et barrière aux vapeurs et liquides du Polyéthylène sur une gamme de température étendue constitue un nouveau challenge scientifique et environnemental. Dans cette étude, nous avons tout d’abord étudié l’impact de charges inorganiques et d’un recuit à 125°C sous air sur les propriétés thermomécaniques d’un HDPE. Le deuxième axe de recherche s’est concentré sur l’amélioration des propriétés barrière aux essences de ce polymère en favorisant les charges lamellaires pour leur haut facteur de forme induisant un effet de tortuosité élevé. L’impact de ce type de charges sur les phénomènes de sorption et d’extraction a été étudié dans le but de définir une formulation à base HDPE optimale pour limiter la perte physique d’oligomères et d’antioxydants. Le but de ces travaux étant de mieux comprendre les différents mécanismes mis en jeu, nous avons cherché à établir les relations Structure / Morphologie / Propriétés pour les deux axes d’étude développés / In the recent years, the use of polyolefin and especially Polyethylene are of economic interest resulting in a growing attention concerning the improvement of its properties of use, especially for automotive application. In this context, the reinforcement of its thermomechanical properties and the improvement of its barrier properties to different fuels over an extended temperature range constitute a major scientific and environmental challenge. In this study, we first decided to analyze the impact of silica particles and of an annealing at 125°C under air atmosphere on thermomechanical properties of a HDPE. The second area of research was focused on the improvement of its barrier properties to fuels by the addition of lamellar charges known for their high aspect ratio inducing a tortuosity effect. The impact of these particles on sorption and extraction phenomena was also studied to determine an optimal HDPE-based formulation in order to limit the physical loss of oligomers and antioxidants. The guideline of this project was the determination of Structure / Morphology / Properties relationships to have a better understanding of the involved mechanisms

There is a high dependency on accurate finite element models in the packaging industry for concept selection, design and virtual validation of packages. One of themost used materials for these packages is High-Density Polyethylene (HDPE). Thismaterial is highly anisotropic, strain rate dependent and has different behavior intension and compression.The objective of this thesis is to improve the existing constitutive model of HDPEthrough additional material characterization experiments and validate those models.For this purpose, strain rate dependencies of the material on elastic and hardeningresponse are included in the constitutive model. In addition to that, the compressivebehavior of HDPE was incorporated in the model as well. The anisotropy of HDPEwas modeled using the Hill48 yield criterion which was characterized by performingmultiple uniaxial tensile tests in the three directions: Machine Direction (MD), 45◦and Cross Direction (CD).Validation was done on the coupon test and compression test on the package.The result displayed that the results from the physical test are comparable with theresults obtained from the FE-models.From the tensile tests, the deformation of HDPE in MD and 45◦ was successfullycaptured and validated. While for the CD direction, the deformation could be captured but not validated against FE-model. Furthermore, the test results displayedthat the material HDPE exhibits a significant degree of anisotropy. In conclusion,the project contributed knowledge and understanding of how a Tetra Pak® packagebehaved during top load compression / Det finns ett stort behov av exakta finita element-modeller inom förpackningsindustrin för konceptval, design och virtuell validering av paket. Ett av de mest användamaterialen för dessa förpackningar är Högdensitetspolyeten (HDPE). Detta materialär mycket anisotropiskt, töjningshastighetsberoende och har olika beteende i dragoch tryckspänning.Syftet med detta projektet är att förbättra den befintliga konstitutiva modellenav HDPE genom ytterligare materialkaraktärisering för experimenten och valideradessa modeller. För detta ändamål ingår töjningshastighet hos materialet för elasticitet och spänning-töjningskurva i den konstitutiva modellen. Utöver det användsäven HDPE:s tryckbeteende i modellen. Anisotropin av HDPE modellerades medanvändning av Hill48 som kännetecknades av att utföra flera enaxliga dragtester itre riktningar: Machine Direction (MD), 45◦ och Cross Direction (CD).Validering gjordes på dragprovstestet och trycktestet på förpackningen. Resultatet visade att resultaten från det fysiska testet är jämförbara med resultaten frånFE-modellerna.Från dragprovstesterna fångades och validerades deformationen av HDPE i MDoch 45◦framgångsrikt. Medan för CD-riktningen kunde deformationen fångas meninte valideras mot FE-modellen. Testresultaten visade också att materialet HDPEuppvisar en betydande grad av anisotropi. Sammanfattningsvis bidrog projektet medkunskap och förståelse för hur ett Tetra Pak®-paket betedde sig under trycktest

A reciclagem de refugos é um processo estratégico que viabiliza a expansão do mercado de plásticos, podendo gerar novos produtos. A obtenção de blendas poliméricas é uma alternativa nesse processo, já que é conhecida a perda de propriedades mecânicas dos termoplásticos nas etapas de reprocessamento. Neste trabalho, o polietileno de alta densidade (PEAD) reciclado teve adições de borracha do monômero etileno-propileno-dieno (EPDM) puro em baixos teores (1 %, 5 % e 10 %), cujo objetivo foi formar blendas miscíveis e um produto final mais resistente ao impacto. O PEAD foi submetido a quatro ciclos de moagem, extrusão e injeção (reprocessamento) e misturado ao EPDM puro por extrusão sem o uso de qualquer aditivo. Os grânulos da blenda formada foram usados para confeccionar os corpos-de-prova por injeção para seu uso nas distintas metodologias analíticas. O processo de irradiação gama foi aplicado nas doses de 50 kGy e 100 kGy e os parâmetros físico-químicos e mecânicos dessas amostras foram comparados aos das não irradiadas. Tanto as blendas irradiadas como as não irradiadas mostraramse visualmente e microscopicamente homogêneas, indicando a compatibilidade da mistura, que também é verificada por seu comportamento térmico. Os parâmetros mecânicos provenientes dos ensaios de tração e flexão, foram semelhantes nas amostras do termoplástico virgem e do reciclado; o processo de irradiação nas blendas gerou sua reticulação, sendo esta verificada não só pelo aumento dos valores desses parâmetros como também pelo aumento da fração gel. A resistência ao impacto aumentou cerca de duas vezes e meia nas amostras com maior teor de EPDM e cerca de 6 a 7 vezes nestas mesmas amostras irradiadas a 50 kGy e 100 kGy respectivamente. O novo material obtido tem fortes indicativos para a sua utilização na pequena e média indústria de plástico, uma vez que já com 1 % de EPDM apresentam melhores características mecânicas em relação ao termoplástico reciclado quatro vezes e essas características foram incrementadas após o processo de irradiação gama. / Waste recycling is a process that allows for advances in plastics industry, particularly when new products are developed. Thus polymer blending is an alternative to recycling processes, since degradation of the mechanical properties of thermoplastics occurs during the reprocessing stages of the material. In this work, high density polyethylene (HDPE) was recycled and mixed to ethylene propylene diene pristine rubber (EPDM) in low concentrations (1%, 5 % and 10 %) to obtain a miscible blend and a final product with high resistance to impact. Pristine HDPE was submitted to four cycles of milling, extrusion and injection (reprocessing) and then mixed with EPDM by extrusion, free of any additives whatsoever. The resulting material was then injected to obtain standard samples submitted to several analytical methods during this research. Also, gamma irradiation process was performed with 50 kGy and 100 kGy absorbed doses; the physical-chemical and the mechanical parameters of these samples were compared to non-irradiated samples. Irradiated and non-irradiated blends were visually and microscopically homogeneous. This indicates a compatible mixture, something which was also verified from analysis of their thermal behavior; mechanical parameters such as stress-strain and flexural curves were similar for pristine and recycled HDPE thermoplastic. On the other hand, the irradiation process on blends generates thermoplastic molecular cross-linking which is verified from increased strength values of mechanical and gel fraction tests. Impact resistance had a 2.5 fold increase with samples with higher EPDM content and about 6-7 fold increase on irradiated samples with 50-100 kGy respectively. These new materials are aimed to small and medium-scale industries, for adding as low as 1% EPDM to the blends sharply improves their mechanical characteristics when compared to recycled thermoplastic. Also, these characteristics improve even further when these materials are gamma irradiated.