With sufficient time, a high density polyethylene geomembrane will degrade and lose its engineering properties until ruptures signal the end of its service-life. This thesis examines the longevity of nine different geomembranes; five of them were of different thickness manufactured from the same resin. The degradation of properties and time to failure are investigated for geomembranes: in immersion tests; as a part of a landfill composite liner; and, exposed to the elements. The different thermal and stress histories associated with manufacturing geomembranes of different thickness are shown to affect their morphological structure; consequently, their stress crack resistance. When immersed in synthetic leachate, it was found that: (a) thicker geomembranes have a longer antioxidants depletion time but the effect of thickness decreases with temperature and is less than expected; (b) inferences of geomembrane’s longevity based on its initial properties may be misleading because a geomembrane may chemically degrade (as manifested by the change in melt index) despite the presence of a significant amount of stabilizers (as manifested by the measured high pressure oxidative induction time); and, (c) stress crack resistance may change before antioxidant depletion or chemical degradation takes place, likely, due to changes in geomembrane morphological structure with the maximum decrease being observed at 55oC. Reductions also were measured for geomembrane immersed in air and water at 55oC. The geomembrane aged in a simulated landfill liner at 85oC is shown to have service-life as little as three years with 30,000 to >2.0 million ruptures/hectare at failure. For exposed geomembranes in Alumbrera (Argentina), samples were exhumed from two mine facilities after ~16 years of exposure. The antioxidants in exposed samples depleted to residual and the stress crack resistance had dropped to as low as 70 hours. Samples were exhumed from a different exposed geomembrane in a test site in Godfrey (Canada) after six years of exposure. The antioxidants were partially depleted, with depletion to residual projected to take at least 20 years; however, despite no evidence of chemical ageing, the stress crack resistance had decreased from 330 to 190 hours, likely due to changes in the morphological structure of the geomembrane. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2014-02-28 04:59:20.834

Made available in DSpace on 2014-12-17T15:41:43Z (GMT). No. of bitstreams: 1 LuziaPFCG.pdf: 2749949 bytes, checksum: 3f79f78a7f602972e60d8e39c6c0e5d4 (MD5) Previous issue date: 2007-11-19 / The biodiesel is defined as the mono-alkyl ester derived from long-chain fatty acids, from renewable sources such as vegetable oils or animal fat, whose use is associated with the replacement of fossil fuels in diesel engine cycle. The biodiesel is susceptible to oxidation when exposed to air and this process of oxidation affects the quality of fuel, mainly due to long periods of storage. Because of this, the oxidation stability has been the focus of numerous researches since it directly affects the producers, distributors and users of fuel. One of the possibilities to increase the resistance of biodiesel is the autoxidation treatment with inhibitors of oxidation. The antioxidants can be used as potential inhibitors of the effects of oxidation on the kinematic viscosity and the index of acidity of biodiesel, thereby increasing oxidative stability. This work aims to examine the efficiency of antioxidants, α-tocopherol and butylated hydroxy-toluene (BHT), added the biodiesel content of remembrance through Pressurized-Differential Scanning Calorimetry (P-DSC), Thermogravimetry (TG) and Petrology. The results showed that the use of antioxidant BHT, at the concentration of 2000ppm, increased resistance to oxidation of the biodiesel and oxidative induction time (OIT), which is a better result as antioxidant than the α-tocopherol. With the thermogravimetric analysis, it was observed that the biodiesel presented an initial decomposition temperature of lower tendency than that of oil, demonstrating to be more volatile, bearing great similarity to the diesel and being characterized as an alternative fuel. The rheological analysis indicated that each sample of biodiesel behaved as a Newtonian fluid / O biodiesel ? definido como o derivado mono-alquil ?ster de ?cidos graxos de cadeia longa, proveniente de fontes renov?veis como ?leos vegetais ou gordura animal, cuja utiliza??o est? associada ? substitui??o de combust?veis f?sseis em motores ciclo diesel. O biodiesel ? suscept?vel ? oxida??o quando exposto ao ar e este processo de oxida??o afeta a qualidade do combust?vel, principalmente em decorr?ncia de longos per?odos de armazenamento. Em fun??o disso, a estabilidade ? oxida??o tem sido foco de in?meras pesquisas, pois afeta diretamente os produtores de combust?veis, distribuidores e usu?rios. Um das possibilidades de aumentar a resist?ncia do biodiesel ? autoxida??o ? o tratamento com inibidores de oxida??o. Os antioxidantes podem ser utilizados como poss?veis inibidores dos efeitos da oxida??o sobre a viscosidade cinem?tica e o ?ndice de acidez do biodiesel, aumentando assim estabilidade oxidativa. Este trabalho teve objetivo de examinar a efici?ncia dos antioxidantes, α-tocoferol e o hidr?xi-tolueno butilado (BHT), adicionado no biodiesel met?lico de mamona, atrav?s da Calorimetria Explorat?ria Diferencial sob Press?o (P-DSC), Termogravimetria (TG) e PetroOXY. Os resultados obtidos mostraram que o uso do antioxidante BHT, na concentra??o de 2000ppm, aumentou a resist?ncia ? oxida??o do biodiesel e tempo de indu??o oxidativa (OIT), revelando-se um melhor resultado como antioxidante do que o α-tocoferol. Na analise termogravim?trica, observou-se que o biodiesel apresentou uma temperatura de decomposi??o inicial menor que a do ?leo, demonstrando ser mais vol?til, aproximando-se do diesel e se caracterizando com combust?vel alternativo. As an?lises reol?gicas indicaram que cada amostra do biodiesel comportou-se como fluido newtoniano