This dissertation discusses the oxidation behavior of reactive membranes that were produced by solution casting and by melt extrusion. These films, containing styrene-butadiene-styrene (SBS) block copolymer that undergoes catalytic oxidation, are of potential use as an oxygen scavenging polymer (OSP) for barrier applications. A thin film kinetic model was developed to ascertain reaction parameters that were used to describe thick film oxidation behavior. Ultimately complex structures containing these scavengers need to be produced via melt-extrusion. Therefore, processing conditions were established to ensure that melt-processed films have the same oxidation kinetics and capacity as those prepared by solution casting. Blends containing a non-reactive styrene phase and an oxygen-scavenging SBS phase were extruded and, by uptake and permeation experiments, their oxidation behaviors were monitored. The flux behavior and time lag extension as a function of oxygen pressure, film thickness, SBS scavenger and photoinitator contents were measured and compared to the theoretical model. The permeation behavior of the reactive blend films containing SBS showed that time lags can be extended via an oxidative mechanism and barrier properties be improved compared to traditional packaging membrane of native polystyrene. / text

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The thermally induced reaction of halogenated ethylenes on the α-Cr₂O₃ (101̅2) single crystal surface results in the formation of gas phase hydrocarbons including acetylene, ethylene, butadiene, and dihydrogen, and deposition of surface chlorine adatoms. No surface carbon or combustion products are observed in any reactions indicating no thermally induced C-C bond cleavage occurs and surface lattice oxygen is not incorporated into surface intermediates. Thermal desorption spectroscopy indicates that in all halogenated ethylene reactions acetylene is the major product, regardless of the reaction scheme. The surface reactions of halogenated ethylenes are proposed to proceed through C-X (X=halogen) bond cleavage to form surface halogen adatoms and surface C2 hydrocarbon fragments. Halogen adatom deposition affects reaction barriers to hydrocarbon formation, and eventually shuts down surface chemistry. Photoemission and near edge x-ray absorption fine structure spectra show that all studied reactants undergo some C-X bond cleavage upon low temperature adsorption forming adsorbed C2 fragments and halogen adatoms. Photoemission for each reaction system shows at least two C1s features (283.0-286.0 eV) and two Cl2p features (2p_3/2=198.0-201.0 eV) with higher binding energy features associated with molecularly intact halogenated ethylenes and lower binding energy features associated with dissociated surface species. Near edge x-ray absorption fine structure spectra taken, corresponding to photoemission spectra, indicate the occurrence of C1s→π∗ transitions, indicating intact π-systems are present. Heating the surface results in a reduction in intensity of higher energy photoemission and near edge x-ray absorption fine structure indicative of a decrease in surface C-X bonds. / Ph. D.

Astronomical and cosmological observations reveal that the majority of the matter in our universe is made of an unknown, non-luminous substance called dark matter. Many experimental attempts are underway to directly detect particle dark matter, which is very difficult to measure due to the expected low interaction rate with normal matter. DEAP-3600 is a direct dark matter search experiment located two kilometres underground at SNOLAB, in Sudbury, Ontario. DEAP-3600 will make use of liquid argon as the detector material, which scintillates as charged particles pass through. The work presented here is an investigation of expected background sources in the DEAP detector. Because DEAP-3600 is a noble liquid-based experiment, a thin film of [1,1,4,4]-tetraphenyl-[1,3]-butadiene (TPB) is coated on the detector walls to shift the scintillation peak from the UV to visible regime for detection. However, alphas passing through TPB produce scintillation signals which can mimic recoil events. Because scintillation properties can change with temperature, we have conducted an investigation of alpha-induced TPB scintillation at temperatures ranging from 300 K to 3.4 K. We were able to characterize the light yield and decay times, and demonstrated that these background events should be distinguishable from true recoil events in liquid argon, thus enabling DEAP-3600 to achieve higher dark matter sensitivity. Additionally, we investigate the performance of the liquid argon purification systems, specifically the activated charcoal used for radon filtration. Previous measurements with the DEAP prototype experiment have demonstrated the necessity of removing radon from the argon prior to filling the detector, due to the release of contaminates from the argon storage systems. Charcoal radon filters are extremely efficient, however, if the emanation rate of the charcoal is too high, there is the possibility of re-contamination. We performed a measurement of the radon emanation rate of a charcoal sample using a radon emanation and extraction system at Queens University. We demonstrated that the emanation rate of the charcoal was consistent with zero. We also show that the number of residual radon atoms which reach the detector would not be an issue for DEAP-3600. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2013-10-10 18:36:40.2

Polybutadiene, the homopolymer of 1,3-butadiene, is a synthetic rubber especially important in the production of tires. Industrially, it is polymerized using multi-site catalysts that do not offer significant control over molecular weight distribution resulting in polymers with poor mechanical properties. Single-site polymerization of 1,3-butadiene results in narrow molecular weight distribution and thus increased impact resistance and durability. Complexes of chromium and neodymium bearing bis-phosphinimine pincer ligands have been synthesized and studied for their behavior in 1,3-butadiene polymerization in combination with methylaluminoxane. The complexes that were active produced highly cis-1,4-polybutadiene with high molecular weight and narrow polydispersities. The co-polymerization of acrylonitrile and 1,3-butadiene with the bis-phosphinimine chromium (III) complexes and methylaluminoxane to produce nitrile-butadiene rubber was also explored. The insertion of 1,3-butadiene into nickel-methyl and nickel-hydride complexes bearing the bis-phosphinimine pincer ligands was examined using nuclear magnetic resonance spectroscopy and will also be discussed.

Polybutadiene, the homopolymer of 1,3-butadiene, is a synthetic rubber especially important in the production of tires. Industrially, it is polymerized using multi-site catalysts that do not offer significant control over molecular weight distribution resulting in polymers with poor mechanical properties. Single-site polymerization of 1,3-butadiene results in narrow molecular weight distribution and thus increased impact resistance and durability. Complexes of chromium and neodymium bearing bis-phosphinimine pincer ligands have been synthesized and studied for their behavior in 1,3-butadiene polymerization in combination with methylaluminoxane. The complexes that were active produced highly cis-1,4-polybutadiene with high molecular weight and narrow polydispersities. The co-polymerization of acrylonitrile and 1,3-butadiene with the bis-phosphinimine chromium (III) complexes and methylaluminoxane to produce nitrile-butadiene rubber was also explored. The insertion of 1,3-butadiene into nickel-methyl and nickel-hydride complexes bearing the bis-phosphinimine pincer ligands was examined using nuclear magnetic resonance spectroscopy and will also be discussed.

The polymer materials industry is heavily dependent on the use of petroleum based plastics. This poses a problem, as the world is facing ongoing petroleum supply problems. A need exists for a bio-carbon based polymer material that has the performance and cost of currently used petroleum plastics. However, the overall performance of current bio-based plastics indicate that they must be somehow supplemented to achieve the properties of that of petroleum-based polymers. The low impact strength and thermal stability of poly(lactic acid), PLA are targets for improvement. One option is for development is through blending with acrylonitrile butadiene styrene (ABS). The viability and efficacy of using these two polymers as blending partners is investigated. The PLA used in these studies has unique and interesting crystallization properties. These have been examined and detailed in part 1. The second part of study includes neat polymer properties, miscibility analysis, and large scale process results. This results in an optimized blending ratio on which to go forward with development. The mechanical, thermal, and morphological properties are investigated in these studies. Significance of this research and development is widespread, as the material developed has the potential to reduce the use of petroleum-based carbon in plastics. / The financial support from the 2010 Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA)/University of Guelph -Bioeconomy for Industrial Uses Research Program, Natural Sciences and Engineering Research Council (NSERC) AUTO21 NCE project and Grain Farmers of Ontario (GFO), to carry out this research is gratefully acknowledged.

The objective of this study was to compare different modifiers in two asphalt cements, namely Cold Lake 80/100 obtained from the Edmonton, Alberta refinery of Imperial Oil Limited and a PG 58-28 obtained from a now closed refinery in the Montreal, Quebec area. The modifiers investigated were polyphosphoric acid (PPA), styrene-butadiene-styrene (SBS), and reactive ethylene terpolymer (Elvaloy® RET). The comparisons were done based on both unaged and laboratory-aged materials. The investigation covers high temperature grading using a dynamic shear rheometer (DSR), low temperature grading using a bending beam rheometer (BBR), ductile strain tolerance as measured in the double-edge-notched tension (DENT) test and percentage recovered strain using multiple shear creep recovery (MSCR) test. The Superpave® performance grade span was increased for all modifiers with substantial increases in the high temperature rutting parameter G*/sin while the BBR parameters, T(S = 300 MPa) and T(m = 0.3), remained largely unchanged. In the PG 58-28 base asphalt, Elvaloy® modifiers were able to reduce the intermediate Superpave® grade temperature by significant amounts. All polymer modifiers were good at improving the ductile strain tolerance as measured in the DENT test. In contrast, PPA alone reduces the strain tolerance due to the formation of extra asphaltenes and the likely gelation of the asphaltene-rich phase. Nearly all the modified samples passed the MSCR test except those with poor compatibility (i.e. SBS blended with Cold Lake without sulfur, Elvaloy® systems without acid catalyst, and pure PPA modified systems) or no modifier, which did not reach the required elastic recovery at high levels of non-recoverable compliance. In the BBR test done at low temperatures, all modified systems showed similar elastic recovery and viscous (non-recoverable) compliance. However, in the ductile-to-brittle range the Elvaloy® RET-modified binders showed a definite advantage of a few degrees over the unmodified base asphalts. Finally, chemical aging tendencies, as measured by weight gain and carbonyl formation, turned out to be very similar for all the investigated compositions. / Thesis (Master, Chemistry) -- Queen's University, 2010-12-13 13:29:45.173

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 61-63). Also available on the Internet.