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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Agro-process intensification using nano-structured micro-porous polymers as soil additives to enhance crop production

Fleming, Steven January 2012 (has links)
Polymerised High Internal Phase Emulsion Polymer (PHP) is a nano-structured microporous polymeric material with a variety of applications. PHPs may have a role to play in sustaining or enhancing crop yields in increasingly alien environments. An elastic hydrophilic version has been developed that has been shown to increase crop yields when used as a soil additive. Soil is a natural carrier of water and nutrients as well as bacteria all of which are widely distributed in the soil and inefficiently maintained and utilised by plants. When polymer is added to the soil, water is attracted to the polymer because of its hydrophilic nature, then roots are attracted to the water and nutrients (if present) in the polymer and they become intimately associated with PHP which therefore brings the plant into close proximity with any fertiliser and bacteria loaded into the polymer. Hence the polymer promotes the interactions between water/nutrients/bacteria/plant roots as well as root exudates within microscopic scale acting as a synthetic rhizosphere which benefits the plant in three ways: (1) Efficient water utilisation and conservation by the plant thus allowing plants to grow in drier environments than would otherwise be possible. The dry weight of soybean shoots with PHP added was increased over 100% compared to plants with no PHP. (2) By adding a fertiliser component to the polymer it can act as a slow release fertiliser, releasing the fertiliser in close proximity to the plant roots, so a larger proportion is utilised by the plant rather than being leached away as normally happens when fertiliser is added direct to the soil. By modifying the production method of PHP so that it contained ammonium sulphate, a major component of many fertilisers, the dry weights of soybean shoots and pea shoots were increased by 66% and 48% respectively after 6 weeks growth. (3) By loading the polymer with beneficial bacteria and fungi, in particular nitrogen fixing bacteria and mycorrhizal fungi, it then offers a protective environment for the organisms which then have a competitive advantage over other soil organisms so their numbers can increase enabling them to make a significant contribution to the nutrient requirements of the plants, in particular nitrogen. The addition of PHP soaked with Azospirillum brasilense broth produced a dry weight increase in grass shoots of 9.6%, 9.5%, 40% and 145% after 3, 6, 9 and 12 weeks growth respectively compared to plants with no PHP or bacteria
2

Preparation of novel composite polyHIPE polymers and their applications in intensified removal of tars from syngas

Hasan, Hasni January 2013 (has links)
In this study, several techniques were applied in order to produce PolyHIPE Polymer (PHP) with improved morphology and properties. Several types of PolyHIPE Polymers (PHPs), silica, vinyl trimethoxy silane (VTMS), and VTMS-silica PHPs, were successfully produced and compared to basic PHPs. The VTMS-silica PHP produced has the highest surface area, followed by silica-PHP and then by VTMS- PHP when compared to typical (basic) PHP. For VTMS PHP, only PHPs with 30, 35 and 40% VTMS exhibit higher surface area than basic PHP. There was no improvement of surface area for PHP with VTMS percentage lower than 30%. All VTMS-silica PHPs have higher pore volume of all types of modified PHPs. The highest pore volume was observed for S30B30, the PHP with 30% VTMS in the oil phase and 30% silica in the aqueous phase. VTMS PHPs with VTMS percentage of 20% and above and silica PHP with 30 % silica have significantly higher pore volume than basic PHP. None of the PHPs showed the existence of micropore volume. Silica and VTMS were successfully reinforced into the HIPE producing novel PHP. This was confirmed by the results produced through FTIR spectroscopy and EDX (Energy Dispersive X-Ray) analysis. Novelty was observed in the morphology of VTMS and VTMS-silica PHP whereas silica-PHP retained the typical morphology of PolyHIPE polymer. The novel morphology of banana-like strands with coral-like pore was produced due to functionalising of VTMS to the HIPE through VTMS incorporation in the oil phase. VTMS-silica PHP is best described as having morphology of knobbly structure produced through incorporation of silica CC30 solution through aqueous phase with VTMS through oil phase. Sulphonated silica-PHP was successfully produced through microwave irradiation and thermal treatment whereas sulphonated-VTMS PHP was successfully produced through thermal treatment only. The sulphonation process decreased the surface area of silica and VTMS PHPs significantly. There was no significant difference between the pore volumes of silica PHPs and those of sulphonated silica PHPs whereas pore volumes of VTMS PHPs decreased significantly due to sulphonation. The sulphonation process retained the morphology of silica and VTMS PHPs except for minor cracks. The project also involved a study on tar removal/conversion using the modified PHP developed in the laboratory, high voltage and non-thermal plasma technique, specifically dielectric barrier discharge. The PHPs combined with dielectric barrier discharge was applied in the fine cleaning system. Due to complexity of the crude oil used as the tar model, no valid conclusion could be made about the tar removal or conversion. However, important positive effects from the treatment were observed in the removal of model tar from the model syngas under electric field or non-thermal plasma.
3

Morphology and tensile properties of polychloroprene

Reeve, Brian January 1972 (has links)
No description available.
4

Synthesis and characterisation of novel isomeric segmented copolymers

Lynch, Sylvie Annie January 2006 (has links)
No description available.
5

Synthesis, mechanical properties and microstructure of carbon nanotube polymer composites

Li, Qianqian January 2006 (has links)
A commercial block copolymer (BC) was first introduced as a dispersing agent to disperse CNTs homogenously in an elastomeric epoxy resin. Single wall CNTs (SWNTs) and multiwall CNTs (MWNTs) were both used to reinforce this epoxy resin. By adding the BC, mechanical properties of CNT/epoxy resin composites were increased dramatically compared to CNT composites without BC. Optical microscopy and scanning electron microscopy were conducted to study the microstructure of CNT/copolymer/epoxy resin composites. It has been confirmed that by using BC, CNTs were dispersed more homogenously in the epoxy resin matrix. Furthermore, improved mechanical properties of composites were achieved by using small amount of BC. The effects of different preparation procedures and different concentrations of materials were also studied. The optimum ultrasonic time and power were decided after trying different options. Ethanol was chosen as a solvent in order to help improving the dispersion. Thus, the optimum proportions of CNT/BC and CNT/epoxy resin were determined for further systematic studies. Finally, SWNT composites and MWNT composites were produced by adding the same mass weight CNTs and by adding the same surface area CNTs. In both cases, SWNT composites presented the best mechanical properties compared to MWNT composites. By adding the same mass weight, the MWNT composites with smaller diameter were stronger because of overall higher surface area; while by adding amounts with the same total surface area, the results were opposite.
6

Polydimethylsiloxane (PDMS) monolayers : morphology, nanostructure, adhesive and frictional properties

Madani, Frederic January 2005 (has links)
In this work polymer and other organic films deposited on silica substrates were studied. Special attention was given to adsorbed polydimethylsiloxane (PDMS) monolayers. Scanning White Light Interferometry (SWLI) is shown to provide direct three-dimensional imaging of thin films with a thickness higher than – 0.5nm. The thickness values are precise (± 0.1 nm) if the system is covered with a metal layer of thickness ~80nm. The lateral resolution is in the sub-microwave range. This makes SWLI a credible alternative to imaging ellipsometry, the standard technique for global imaging of thin and ultra-thin films. SWLI has been used to establish the irreversible nature of adsorption of PDMS on silica. It has also been to judge whether or not a film is a true monolayer through height measurement across the layer. A leap in lateral resolution of two or three orders of magnitude is obtained by using Intermittent Contact Scanning Force Microscopy (IC-SFM). A dense dry PDMS monolayer consists of a bimodal system: a smooth layer made of chains with a flat conformation topped by upright chain segments of poorly adsorbed chains that aggregate to form large spots. The presence of the smooth base layer was verified by means of an SFM tip used as a ‘nanodigger’. Pull-off force experiments carried out in bad solvent conditions between an SFM tip and a PDMS monolayer (contact area ~10nm) have shown two main energy dissipation mechanisms: chain or chain segment stretching, long range adhesive plateaus the length of which is related to chain length. Their height is related to the surface energy of PDMS that was estimated through contact angle goniometry. This phenomenon has been interpreted as the elongation of a collapse chain going from a globule to coil state.
7

The mechanics of polymer pipe deformation in pipeline renewal

Fischer, W. P. January 1993 (has links)
No description available.
8

United Nations peace operations, human security and conflict transformation : the case of the mission in Afghanistan

Hasegawa, Yuka January 2005 (has links)
No description available.
9

The formability of long fibre thermoplastic composites

Steel, David Thomas January 1998 (has links)
No description available.
10

Synthesis and characterization of novel imprinted microgels with hydrolytic catalytic activity

Maddock, Stacey Claire January 2003 (has links)
No description available.

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