Optimisation of the fabrication conditions and characterisation of polymer/OMMT composites microcantilevers
- Authors: Cele, Hastings Mthobisi
- Date: 2015-11-10
- Subjects: Biopolymers , Polymeric composites , Biodegradable plastics
- Type: Thesis
- Identifier: uj:14528 , http://hdl.handle.net/10210/15058
- Description: PhD. (Applied Chemistry) , This dissertation presents work involving novel fabrication conditions of polylactide (PLA) based microcantilevers (μCs) as well as the characterisation of the fabricated cantilever beams. Focused ion beam (FIB) milling and micro-injection moulding were chosen as the fabrication processes during this research. Unfortunately, FIB milling was a time-consuming fabrication technique and could not maintain the shape of the sample. Micro-injection moulding (μIM) was chosen as the main fabrication process of μCs because it is a commercially used technique and can produce many cantilevers per cycle. Before the fabrication of the actual cantilevers, deflection comparison of the two types of cantilevers (Si & polymer) was made using structural mechanics application mode of MEMS module of COMSOL Multiphysics. The simulations showed that polymer μC deflects more than Si μC because of its low Young’s modulus. Another modelling and simulation was made based on the Eigen frequencies of PLA and Si cantilevers with various geometries. The predictions of the modelled cantilever beams depicted that resonance frequency depends on the mechanical properties of the material as well dimensions of the beams. For μIM, a shim-stock mould can be used to produce μCs from a modified PLA extrusion grade.
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Synthesis and characterization of cyclodextrin based chitosan nanoparticles for drug delivery of essential oil
- Authors: Matshetshe, Kabo I.
- Date: 2017
- Subjects: Nanoparticles , Chitosan , Cyclodextrins , Biopolymers , Polymers in medicine
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/235801 , uj:24121
- Description: M.Sc. (Nanoscience) , Abstract: The cinnamomum zeylanicum essential oil (CEO) is a plant extract from Cinnamomum zeylanicum Blume species and possess good antimicrobial activity such as anti-bacterial, anti-viral, anti-fungal, anti-parasitical and insecticidal. However, CEO is a volatile compound which easily decomposes upon direct exposure to heat, pressure, light or oxygen, and is also highly insoluble in water. This study reports the encapsulation of cinnamomum zeylanicum essential oil (CEO) in chitosan nanoparticles (CS-NPs) and β-cyclodextrins based chitosan nanoparticles (β-cyclodextrins/CS -NPs) synthesized via an ionic gelation cross-linking method. The as-synthesised CS-NPs and β-cyclodextrins/CS-NPs loaded CEO were characterized using Ultraviolet and visible (UV-vis) spectrophotometry, dynamic light scattering (DLS), Fourier transform infra-red spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD) and High resolution transmission electron Microscopy (HR-TEM). The properties of CEO-loaded β-CD/CS-NPs and CEO-loaded CS-NPs such as the encapsulation efficiency (EE), surface charge, morphology, and in vitro drug release were investigated. At an optimized conditions, the encapsulation efficiency (EE) of CEO-loaded β-CD/CS-NPs and CEO-loaded chitosan nanoparticles were about 58.03 1.13 % and 20.04 %, respectively, when the initial CEO content was 12.5 mg/mg of chitosan. As determined by TEM and DLS, the individual nanoparticles of CEO-loaded β-CD/CS-NPs and CEO-loaded CS-NPs exhibited a spherical shape with an average size distribution of 36.08 11.25 nm and 111.15 27.88 nm, and a positively charged surface with a zeta potential value of 20.73 3.20 and 30.5 0.72 mV, respectively. The in vitro release of CEO from optimized chitosan nanoparticles showed a sustained release, with release amounts of 49...
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Greener synthesis of biopolymer-inorganic nanocomposite beads and membranes for use in water purification
- Authors: Masheane, Monaheng Leonard
- Date: 2016
- Subjects: Water - Purification - Membrane filtration , Water - Purification , Nanocomposites (Materials) , Nanotechnology , Biopolymers
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/84682 , uj:19251
- Description: Abstract: In South Africa, the unavailability of clean drinking water is a life-threatening problem, especially in the rural areas. Millions of people living in rural areas rely on water directly from the source (surface and groundwater) for drinking, cooking and other domestic purposes without any prior treatment. These sources of water are known to be affected by contaminants from untreated wastewater, industrial effluent, agricultural runoffs and domestic waste. The exposure of humans to these polluted water bodies results in infection and waterborne diseases which sometimes result in death. This has a direct consequence to the productivity of the people living in these communities and has cost implications to the government. This study was aimed at determining the potential pollutants present in drinking water sources in Lochiel, a small community in the Mpumalanga province, eastern part of South Africa, and to develop efficient and cost effective materials (beads and membranes) that could be used in the rural communities to provide safe and clean water for consumption. The application of adsorption materials (e.g. in the form of beads) and filtration materials (e.g. membranes) has attracted great interest in water purification. This is because they have several advantages over the conventional methods. These advantages include but are not limited to low capital and operations costs, low energy requirements (especially when chemically modified) and ease of operation. In this study chitosan (CTs) was chosen to prepare novel and environmentally benign nanocomposite materials either in the form of beads or flat sheet using greener solvents. In an attempt to prepare biopolymer-ceramic nanofiltration composite membranes, small amounts of multiwalled carbon nanotubes (MWCNTs) (5 wt%) and alumina (Al) (20 wt%) were added to CTs in pH controlled aqueous media near room temperature. The resulting nanocomposite was found to readily form insoluble beads... , M.Sc. (Chemistry)
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Extraction of Atropine and Scopolamine from Datura ferox and Datura stramonium.L and sample clean-up using molecularly imprinted polymers
- Authors: Nobaza, Kwindla Handy
- Date: 2014-09-16
- Subjects: Botanical chemistry , Biopolymers , Plant polymers , Plant extracts , Phytochemicals
- Type: Thesis
- Identifier: uj:12311 , http://hdl.handle.net/10210/12097
- Description: M.Sc. (Chemistry) , The extraction of the atropine and scopolamine alkaloids from both Datura ferox and Datura stramonium was carried out in this study to investigate potential of these plants as a source of these alkaloids. Tropane alkaloids such as atropine occur naturally in many members of several plant families, especially the Solanaceae, Erythroxylaceae, Proteaceae and Convolvulaceae families. Hyoscyamine or its racemic mixture atropine is used as an antidote to organophosphate insecticides, or as a nerve agent to dilate the pupil for retina examinations. Scopolamine or hyoscine is used to treat motion sickness, among other uses. Tropane alkaloids are often difficult to synthesise, and their extraction from commercial sources is therefore of some commercial interest. A systematic study was carried by comparing different extraction methods for the efficiencies of tropane alkaloid (TA) extraction at ambient pressure. The two plants selected are already widely spread as weeds in many regions in South Africa and are therefore well adapted to the local conditions. Among the extraction methods, TA’s were extracted in their acidic form using dilute aqueous acids with 5% sulfuric acid giving the highest yield of both atropine and scopolamine. Alternatively, the TA’s were extracted in their basic form from the plant material using basified organic solvents. The overall yields obtained were not significantly different from those obtained by using dilute aqueous acids, with D. ferox giving approximately 0.24 % and 0.0028 % scopolamine and atropine, respectively. D. stramonium on the other hand gave approximately 0.037 % and 0.002% atropine and scopolamine, respectively. Different plant parts were also tested in order to determine if there was an advantage in extracting the tropane alkaloids at a particular time in the growth, but concluded that the best option was to extract the seeds for various reasons such as the presence of relatively less chlorophyll...
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Early transition metal carbides-multiwalled carbon nanotubes-biopolymer nanocomposites in the application of hydrostatic pressure sensor
- Authors: Makhado, Bveledzani Pertunia
- Date: 2019
- Subjects: Pressure transducers , Hydrostatic pressure , Transition metal carbides , Carbon nanotubes , Nanocomposites (Materials) , Biopolymers , Cellulose acetate
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/417534 , uj:35364
- Description: Abstract: Pressure sensors are very significant and are used in various areas such as automobiles, aerospace, medical industry, energy storage, corrosion protection, electrochromic devices, electrochemical sensor. Most of the pressure sensors in the market are intended to operate either in the air, dry gases and water-based environments. Environmental interference hampered the pressure sensors effectiveness and life cycle. As a consequence, countless measurement and reading mistakes have been reported owing to interferences such as trapped air in a cylinder and elevated humidity, thus decreasing sensitivity and delaying response time. In this study, we determine the resistance sensitivity of a hydrostatic pressure sensor based on cellulose acetate (CA), alpinumisoflavone (BI), multiwalled carbon nanotubes (MWCNTs) and metal carbides (MC) nanocomposites deposited on integrated electrode. We intended to utilize a cost-effective, simple, fast deposition process and fabrication of thermoplastic polymers nanocomposites for pressure sensing device and to study electrical properties of pressure sensing and stability using LCR meter... , M.Sc. (Nanoscience)
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