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Studies on vinyl cations and unsaturated carbenes.Liang, Wei Chuan January 1972 (has links)
No description available.
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Studies on vinyl cations and unsaturated carbenes.Liang, Wei Chuan January 1972 (has links)
No description available.
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Reactions of organolithiums with a variety of vinyl chlorides /Valcho, Joseph James January 1975 (has links)
No description available.
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Structure and Properties Of dimethacrylate-Styrene Resins and NetworksBurts, Ellen 04 December 2000 (has links)
One of the major classes of polymer matrix resins under consideration for structural composite applications in the infrastructure and construction industries is the dimethacrylate matrix resin. An investigation of the relationships between the chemical structures and properties of these dimethacrylate/styrene networks has been conducted. Oligomer number average molecular weights of the polyhydroxyether ranging from 700 to 1200g/mole were studied with systematically varied styrene concentrations to assess the effects of crosslink density and chemical composition on glass transition temperatures, toughness, tensile properties and matrix strain. Network densities have been estimated from measurements of the rubbery moduli at Tg + 40°C. Within this rather small range in vinyl ester molecular weight, toughness of the resultant networks improved tremendously as the vinyl ester oligomer Mn was increased from 700g/mole to 1200g/mole due to improvements in the resistance to crack propagation. As styrene concentration was increased along all series' of materials, brittleness increased even though the molecular weight between crosslinks increased. This was attributed to the inherent relative brittleness of the polystyrene chemical structure relative to the polyhydroxyether component. This may also be related to the reactivity ratios dictating styrene and vinyl ester sequence length and warrants further investigation. As expected, the volume contraction upon cure also decreased significantly as styrene was decreased, and thus residual cure stresses may be reduced in fiber-reinforced composites. Vickers microhardness values decreased for each of the series when molecular weight increased and styrene content decreased.
Two different cure procedures were compared to assess the effects of conversion on the physical and mechanical properties. All mechanical properties investigated (i.e. fracture toughness, tensile strength, and microhardness) were dependent on the cure procedure. Materials cured at 140°C were harder, more brittle, had lower elongations and higher rubbery moduli than those cured at 25°C followed by a 93°C postcure. A maximum in the degree of conversion occurred with increasing polymerization temperature and can be explained by the competition between the chemical reaction and molecular mobility. The overall shrinkage per moles of vinyl groups converted was the same when the materials were cured at 25°C or 140°C. However, in the room temperature cured samples, there was essentially no further densification of the network during postcure, regardless of the postcure temperature. A mono-methacrylate analogue of the dimethacrylate terminated poly(hydroxyether) oligomer was synthesized and copolymerized with styrene to study the effects of chain transfer during elevated temperature reactions. / Ph. D.
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New developments in Ramberg-Bäcklund and episulfone chemistryJohnson, Paul January 1999 (has links)
No description available.
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Enhancing Fracture Toughness and Thermo-Mechanical Properties of Vinyl-ester Composites Using a Hybrid Inclusion of CNT and GNPUnknown Date (has links)
We report a method of increasing fracture toughness (KIc) and strain energy release rate (GIc) of vinyl-ester (VE) matrix by adopting a hybrid (dual) reinforcement strategy. The idea of using this strategy was to trigger intrinsic polymer-nanoparticle interaction such as carbon nanotube (CNT) pull-out and interface sliding to enhance energy absorption during fracture. Additionally, we included a second reinforcement, graphene nanoplatelets (GNP), to promote crack-deflection, crack bridging and cross-linking density. Both reinforcements were dispersed into the polymer in three states: non-functionalized (nf>); functionalized with COOH (f>); surface-treated with Triton X-100 (TX100). We embarked on numerous experiments with many combinations of these variables. We measured KIc and GIc using ASTM D5045-14. We conducted an exhaustive iterative investigation with three systems (f>CNT-VE; f>GNP-VE; f>CNT-f>GNP-VE) to determine the best weight-percentage for the nanocomposite system that produced the highest KIc and GIc values when compared to neat-VE. We found that 0.5wt% f>CNT with 0.25wt% f>GNP in the VE matrix resulted in the highest fracture toughness values and was termed the optimized hybrid nanocomposites (OHN) system. Subsequently, we explored further increasing the KIc and GIc of OHN through altering the nanoparticle surface characteristics, which led to four OHN groups: f>CNT-f>GNP-VE; f>CNT-f>GNP-TX100-VE; nf>CNT-nf>GNP-TX100-VE; nf>CNT-nf>GNP-VE. We discovered that the OHN group with non-functionalized nanofillers that were TX100 surface treated (0.5wt%nf>CNT-0.25wt%nf>GNP-TX100-VE) generated the greatest improvements in KIc and GIc.
Ultimately, we observed that the KIc of neat-VE increased by 65%, from 1.14 to 1.88 MPa*(m½). The improvement in GIc was even greater with an increase of 166%, from 370 to 985 J/(m2). Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) studies showed a minor shift in glass transition temperature (Tg) by up to 8°C when comparing neat-VE specimens to OHN specimens. A similar increase in maximum thermal decomposition temperature (Tp) of up to 8°C was observed through thermogravimetric analysis (TGA) and derivative TGA (DTG). Scanning electron microscope (SEM) studies revealed that the source of improvements in fracture toughness and thermal properties was primarily the three-dimensional hybrid nanostructures (3DHN) that formed by binding CNT and GNP together, which caused an increase in nanoparticle surface area and inhibited agglomerations. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection
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Photophysics studies of poly (2-vinyl fluorene) by laser fluorimetry.January 1985 (has links)
by Chow Kim-fung. / Bibliography: leaves 112-114 / Thesis (M.Ph.)--Chinese University of Hong Kong, 1985
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Microcosm study of enhanced biotransformation of vinyl chloride to ethylene with TCE additions under anaerobic conditions from Point Mugu, CaliforniaPang, Incheol Jonathan 25 September 2000 (has links)
This microcosm study demonstrated the enhanced anaerobic transformation
of vinyl chloride (VC) to ethylene. A previous microcosm study from Point Mugu
site showed the accumulation of VC due to the slow transformation step of VC to
ethylene. To overcome the rate-limiting step, two laboratory experiments tested the
effect of trichloroethylene (TCE) additions on the rate enhancement, repeated low
TCE additions and high TCE concentration additions.
TCE (2 ��mol) was repeatedly added over a two week interval. In a parallel
study, an equal amount of VC was added to another set of microcosms. TCE
addition increased VC transformation to ethylene, with nearly 19% VC conversion
to ethylene compared to 4% VC conversion in the VC added controls. However,
the increased VC transformation rates were not sufficient enough to avoid VC
accumulation. Rate of VC transformation decreased once TCE addition was stopped. This indicated the mixed culture required the transformation of TCE to
maintain VC transformation rates.
With TCE added at high concentrations (100 mg/L and 200 mg/L), nearly
complete transformation of TCE to ethylene was observed. After the addition of
high TCE concentrations, low concentration TCE (3 ��mol) was added and near
95% transformed to ethylene in 45 days. Two different low hydrogen yielding
substrates, butyrate and propionate, were tested. Both were equally effective in
promoting TCE dechlorination. Methanogenesis was inhibited at high TCE
concentration with both substrates. Kinetic analysis of VC transformation data
showed VC transformation followed the first order kinetics with respect to
concentrations using a modified Monod equation. First-order kinetic constants
increased after the addition of high ICE concentrations. After 200 mg/L of TCE
addition, the first-order kinetic constant increased by factor of six compared to the
rate obtained from the earlier low TCE concentration addition. However,
reintroduction of TCE at low concentration maintained similar enhanced kinetic
constants, as achieved at high concentration. This indicated the enhancement of
VC transformation to ethylene was likely due to the growth of microorganisms
using TCE as a terminal electron acceptor. These microorganisms were likely
responsible for the transformation of VC to ethylene. / Graduation date: 2001
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µLSu, Min-Chen 26 July 2000 (has links)
none
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Life cycle cost analysis -With focus on the floor types, linoleum and vinyl with or without PUR reinforced surfaceMiletic, Martin, Samuelsson, Andreas January 2014 (has links)
The flooring industry is a market that constantly changing every year with new products and improvements. The purpose of this report is to uncover which of the floors, linoleum and vinyl with or without PUR reinforced surface has the lowest life cycle cost for the customer over a 30-year period. The scope of the study is to investigate the three different floors in the public sector in Sweden, Norway, and Finland. A similar study was made many years ago where remarkable result was uncovered. The way used to determining the result in this study is made by two different methods within the LCC. The LCC calculations in this study are based on the primary data collections; qualitative interviews, time study, and observations. Secondary data have also been used in the report. When a customer invests in a floor there are three major costs purchasing, installation, and maintenance. Maintenance will ultimately be the biggest cost because it extends over the entire life cycle while the others are two fixed costs. The analysis uncover that the amount of water and chemical usage to maintain the floors has reduced since the old study. The consumption that has increased is the energy, a result from the increase usage of cleaning machines in the public sector. The most profitable floor to invest in is the vinyl with PUR reinforced surface. This floor has in Sweden and Norway a higher purchasing price than linoleum and vinyl without PUR reinforced surface but in the long run (30 years) its total life cycle cost are lesser than the two others. If the public sector in Sweden invests in a vinyl floor with reinforced PUR surface instead of a vinyl without PUR, the life cycle cost at a hospital or municipality will be reduced by 16,3 percent.
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