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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- 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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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...
- Full Text:
- 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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