An electrochemical urea biosensor on a carbon nanofiber-poly (amidoamine) dendrimer supramolecular-platform
- Authors: Blessie, Wessel
- Date: 2020
- Subjects: Supramolecular electrochemistry , Nanomedicine , Polymeric composites , Carbon composites
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/473889 , uj:42696
- Description: Abstract: The concentration of urea in serum or urine in human body should be in moderate levels (3.3–6.7 mM). The elevation of urea above the normal level indicates gastrointestinal bleeding, obstruction of the urinary tract, burns, shock, or renal failure. The decline in the concentration of urea below moderate levels causes cachexia, hepatic failure, and nephritic syndrome. The increase/decrease in the concentration of urea poses health risks. Thus, it is essential to determine the urea concentration for early diagnosis of kidney related disease. In this mini-dissertation, we report a novel amperometric urea biosensor based on the immobilisation of urease enzyme on carbon nanofiber-generation 3 polyamidoamine dendrimer immobilisation layer on a glassy carbon electrode (GCE). Electrospun polyacrylonitrile (PAN) based carbon nanofibers were obtained with an average diameter of 132 nm through stabilization, electrospinning, and carbonization of polyacrylonitrile (PAN) polymer. The structure and the morphology of the PAN carbon nanofibers were studied by High Resolution Transmission Electron Microscope (HR-TEM) and Field Emission Scanning Electron Microscope (FE-SEM)... , M.Sc. (Nanoscience)
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An investigation into the role of nanoclay and its localization on the micro-structural development and properties of polypropylene-based immiscible blends
- Authors: Mofokeng, Tladi Gideon
- Date: 2018
- Subjects: Nanocomposites (Materials) , Polymeric composites , Polymer clay
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/278759 , uj:29920
- Description: Ph.D. (Chemistry) , Abstract: This study deals with the influence of nanoclay localization on the morphological development and properties of melt-mixed PP/LDPE/clay and PP/EVA/clay nanocomposites. The main objective of this work was to develop PP/LDPE and PP/EVA-based hybrid materials with better compatibility, thermal stability, and impact strength, and at the same time with relatively good strength, flexibility, and elastic modulus. Blends with various compositions were prepared through melt extrusion. The morphological and dynamic characterizations show that the PP/EVA blends were immiscible for the investigated blend compositions. The presence of EVA in PP induced a beta (β)-phase formation of PP, thereby increasing the elongation-at-break and impact strength. The PP/LDPE blend morphology comprised a major matrix phase and a minor phase, with sub-inclusions of the major matrix within the minor phase. The PP/LDPE blends exhibited partial miscibility at low contents (< 20 wt%) of either phase; however, the phases were immiscible at higher contents. The PP/LDPE blend composition and morphology influenced the impact strength and elongation-at-break. The 80/20 PP/LDPE and 80/20 PP/EVA blends offered a balance between the mechanical and material properties essential for flexible packaging applications. Thereafter, 4 wt% nanoclay was added to modify the morphologies of the blends. The PP/LDPE/clay nanocomposites investigated in this study contained two different types of compatibilizers [maleic anhydride-graft polyethylene (PE-g-MA) and maleic anhydride-graft-polypropylene (PP-g-MA)], which manipulated the localization of clay in different phases. The morphological characterization results show that the nano/micro-structure of the PP/LDPE (80/20) blend could be controlled by incorporating the nanoclay alone or by adding a mixture of organoclay and maleated compatibilizers, a feature which significantly improved the thermal stability and tensile and rheological properties of the blend composites. The...
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Corrosion inhibition for mild steel in 1 M hydrochloric acid using synthesised environmentally friendly polymer composites
- Authors: Baloyi, Nomsa Precilla
- Date: 2019
- Subjects: Hydrochloric acid , Polymeric composites
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/413203 , uj:34802
- Description: Abstract: For several decades, mild steel has been an ideal mandated material in many industrial applications. However, unlike stainless steel and other special steel alloys, mild steel is prone to corrosion attack, leading to devastating failures of equipment and metallic structures over time, causing losses worth billions. This situation has spurred researchers to find solutions for the corrosion phenomenon. The present work investigates the inhibition efficiency as a corrosion inhibitor of an ecofriendly and cost-effective composite developed from organic polymers. Synthesis of an environmentally friendly copolymer composite of Polyethylene glycol L-proline (PEGLP), from polyethylene glycol and L-proline, was carried out. A variety of analytical equipment was used to evaluate the characteristics of PEGLP. Results of Fouriertransform infrared spectroscopy, nuclear magnetic resonance spectroscopy, X-ray diffraction, scanning electron spectroscopy-energy dispersive spectroscopy, thermogravimetric and organic elemental analyser analysis show that a composite was produced. Fourier-transform infrared spectroscopy and nuclear magnetic resonance spectroscopy confirmed the presence of –COOH, -C-H, N-C and –OH in the PEGLP molecules, making the PEGLP ideal for corrosion inhibition. Spectroscopy-energy dispersive spectroscopy and organic elementary analysis showed that the mass percentages of nitrogen, carbon and oxygen were higher on the PEGLP than in the starting materials; which confirms that the PEGLP has bulk molecular weight that will improve inhibition efficiency. Thermogravimetric analysis revealed that PEGLP was thermally stable up to 200oC and could be used for a wide range of applications below 200oC without it degrading. Subsequently, the newly synthesised PEGLP was investigated as a corrosion inhibitor for mild steel in 1 M HCl, and its corrosion inhibition properties were studied by means of gravimetric and electrochemical techniques, from which corrosion rate, inhibition efficiency, thermodynamic parameters and adsorption were determined. The gravimetric technique focused on the effects on the mild steel of concentrations of the inhibitor between 200 ppm and 800 ppm, immersion time from 1 h to 9 h, and temperatures from 298 K to 338 K. It was found that an increase in inhibitor concentration led to a decrease in corrosion rate. The optimal concentration, with the... , M.Tech. (Extraction Metallurgy)
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Effect of organically modified layered double hydroxide and thyme oil loading on the performance of Poly(lactic acid) /Poly[(butylene succinate)-co-adipate] biodegradable polymer blends for cosmetics packaging applications
- Authors: Mhlabeni, Thobile L
- Date: 2019
- Subjects: Nanocomposites (Materials) , Polymeric composites , Polylactic acid , Biodegradable plastics , Lactic acid
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/401348 , uj:33537
- Description: Abstract : Poly(lactic acid) (PLA) is a well known biodegradable polymer that can be applied for short term packaging in food and cosmetics. However, PLA is brittle, which significantly limit its industrial packaging applications. Blending PLA and other polymers serve as one of the alternative techniques to improve the toughness of PLA. Blends preparations can be done by melt-compounding using the extrusion technique, which is popular for industrial applications. Blending PLA with equally bio-friendly polymers is preferred to avoid tampering with the degradation rate of PLA. In this study, poly[(butylene succinate) co-adipate] (PBSA) has been investigated as a secondary polymer to improve the flexibility of PLA. Extrusion grades of PLA and PBSA were melt-blended using a twin screw extruder to prepare the PLA/PBSA blends... , M.Tech. (Chemistry)
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Fabrication and characterisation of highly water permeable ultrafiltration membranes as supports for forward osmosis thin film composite membranes
- Authors: Vilakati, Gcina Doctor
- Date: 2015-04-23
- Subjects: Water - Purification - Membrane filtration , Ultrafiltration , Polymeric composites
- Type: Thesis
- Identifier: uj:13564 , http://hdl.handle.net/10210/13704
- Description: Ph.D. (Chemistry) , The ultrafiltration membranes presented in this study were synthesized using the phase inversion method by casting on a nonwoven fabric. The polymer solutions were mixed with synthetic and bio additives in order to improve the resultant membrane performance. Synthetic additives (polyethylene glycol (PEG) and polyvinyl pyrrolidone (PVP)) were compared with a novel and cheap bio additive, lignin. Based on the knowledge that the additives must be soluble in water in order to increase the pore sizes of the membranes, sodium hydroxide was used to elute residual additives that remain in the membrane during coagulation. In order to trace the residual additives remaining, ATR-FTIR was used. Contact-angle analysis and water-absorption experiments were used to elucidate the hydrophilic properties of the prepared membranes. Membranes modified with lignin (Lig) were found to absorb more water (94% water uptake) when compared to the other membranes. In general, the contact angles were found to be low for membranes that were treated with NaOH. Membrane permeability followed the trend, Lig_PSf>PVP_PSf>PEG_PSf which is similar to the trend followed during water uptake. Pore size and pore distribution analysis showed that membranes modified with lignin and PVP had a narrow range (had pore sizes ranging from 10 to 24 nm) compared to that of PEG-PSf membrane (which ranged from 2.5 to 22 nm). A Robeson plot showed that Lig_PSf membranes had high separation factors regardless of the size of the solute being rejected. This study shows the possibility of using cheap and readily available additives to increase the performance of membranes......
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Graphene based molecularly imprinted polymer composites and composite imprinted ultrafiltration membrane for water treatment
- Authors: Kibechu, Rose Waithiegeni
- Date: 2016
- Subjects: Water - Purification - Membrane filtration , Ultrafiltration , Polymeric composites , Graphene
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/124901 , uj:20972
- Description: Abstract: Membranes for water treatment face a major problem of fouling. One of the solutions to reduce fouling propensity in membranes is the addition of hydrophilic additives during membrane preparation. In this study, a significant enhancement of hydrophilicity, flux and rejection of Na2SO4 by a modified polysulfone membrane was observed. The membrane was prepared using graphene oxide (GO) as a hydrophilic additive followed by surface modification through imprinting on Graphene oxide-polysulfone (GO-Psf) mixed composite membranes. GO was synthesized through oxidation and exfoliation of graphite. The GO-Psf composite membrane was prepared through a phase inversion process of a mixture of GO and polysulfone (Psf) in N-methylpyrrolidone (NMP). Imprinting on the surface of composite membrane was achieved through a free radical polymerization. Characterization of the GO and the prepared membranes was achieved using Fourier-transform spectroscopy (FT-IR), Raman spectroscopy, thermogravimetric analysis (TGA), contact angle, scanning electron microscope (SEM) and transmission electron microscope (TEM). FT-IR of the composite imprinted membranes (CIMs) showed new peaks at 935 cm-1 and 1638 cm-1 indicating the success of surface imprinting. Raman spectroscopy was used to confirm the presence of GO in the modified membrane. The CIMs showed improvement in flux from 8.56 LM-2h-1 of neat polysulfone membrane, to 15.3 LM-2h-1 in the CIM. Similarly, rejection of Na2SO4 salt rejection also increased from 57.2±4.2 % of polysulfone membrane to 76±4.5 % in CIMs. The surface modified membranes also showed improvement of surface hydrophilicity; the contact angle measurements for the neat polysulfone membrane was measured to be 72±2.7 % compared to... , Ph.D. (Chemistry)
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Hybrid polymer matrix composites : effects of stainless steel and iron oxide particles
- Authors: Daru, Lydia Haruna
- Date: 2019
- Subjects: Composite materials , Steel, Stainless , Iron oxides , Polymeric composites
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/424663 , uj:36325
- Description: Abstract: Polymers have been in existence since the beginning of time, in different forms such as shell, tar etc. but in the 20th century, it began to be modified chemically and synthetically and its variants became applicable in many industries. Since then, other means of achieving better methods of polymer materials have been explored. This study aims to achieve the use of hybrid of stainless steel and iron (iii) oxide for reinforcing polymer composites by using epoxy resin. Various material characterizations were conducted on the stainless steel, iron (iii) oxide and the hybrid composite material produced by reinforcing it in epoxy resin. To fabricate the samples, the particles were reinforced into the epoxy matrix at different weight percentages. The polymer samples produced were characterized by conducting mechanical and microstructural analysis such as impact, hardness, scanning electron microscopy, and electron dispersive spectroscopy. The results showed that the addition of the iron (iii) oxide particles increases the hardness property of the hybrid polymer composites. The polymer produced with hybrid reinforcements showed higher hardness value when compared to the samples produced with only the epoxy resin without any reinforcement. The application of silane in the hybrid composite makes it to be more brittle. The reinforced composites produced in this research can be recommended for applications where hard and brittle materials are required for the functionalized sample. , M.Ing. (Mechanical Engineering)
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Modification of polyethersulfone by grafting acrylic-acid based monomers for improved hydrophilicity and pH-responsive properties of membranes
- Authors: Kgatle, Masaku
- Date: 2016
- Subjects: Water - Purification - Membrane filtration , Membrane filters , Nanofiltration , Graft copolymers , Polymeric composites
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/124976 , uj:20981
- Description: Abstract: The quality of drinking water is continuously deteriorating due to pollutants that end up in water arising from a variety of industries. These pollutants reduce the value of water thereby posing risks to people’s health and the environment. Thus, there is a need to develop techniques that will be effective in wastewater treatment to obtain potable water. Membrane technology has increasingly become the most reliable, applicable and cost-effective technique for drinking water treatment solution. However, membrane fouling has been identified as the major obstacle to the applicability of this technique. In order to alleviate this issue, many studies have proved that improving the hydrophilicity of a membrane surface is significant. In this study, acrylic acid (AA)-based monomers (acrylic acid (AA), methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA)) were graft-polymerized onto hydrophobic polyethersulfone (PES) using benzoyl peroxide (BPO) as the chemical initiator for the development of membranes with pH-responsive and antifouling properties. The confirmation of successful grafting was done using nuclear magnetic resonance (NMR) and fourier transform infrared (FTIR) spectroscopies. Flat-sheet pristine and grafted PES membranes were prepared by phase inversion via immersion precipitation technique. The morphology of the membranes was studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Furthermore, membrane hydrophilicity and performance were investigated using contact angle measurements and dead-end filtration (pure water flux, bovine serum albumin (BSA) rejection and fouling analysis). The SEM analysis showed an increase in the pore size of the PES-g-PAA, PES-g-PMAA and PES-g-PEGDMA membranes in comparison with the pristine PES membrane. The contact angle measurements indicated significant increases in the hydrophilicities with chemical grafting of the AA-based monomers onto PES. The pH-responsive tests proved that the grafted PES membranes all... , M.Sc. (Chemistry)
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Molybdenum sulfide nanostructures : synthesis and their catalytic applications
- Authors: Madima, Ntakadzeni
- Date: 2017
- Subjects: Water - Purification - Photocatalysis , Nanostructured materials , Polymeric composites , Photocatalysis , Molybdenum compounds
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/235780 , uj:24119
- Description: M.Sc. (Nanoscience) , Abstract: Environmental pollution (i.e. water pollution) has been an issue of great concern across the globe. Water scarcity is reported to be a huge challenge throughout the world. The South Africa water capacity will decrease dramatically in the next 10 years due to various pollutants. Dye molecules such as Methyl Blue (MB) and Rhodamine B (RhB) and heavy metals such as Chromium (Cr(VI)) are reported to be the major cause of water pollution, which results in the scarcity of clean water for human use. These pollutants are present as harmful entities in the environment due to their carcinogenic and mutagenic nature. So, the sustainability of clean water is in greater demand for all forms of life relies upon its availability. Thus the aim of this study was to synthesize molybdenum sulfide nanostructures and its nanocomposite and evaluate their photocatalytic properties towards water treatment. Molybdenum sulfide nanostructures were synthesized via hydrothermal methods using different capping agents namely Polyethylene Glycol (PEG-400) and Ethylenediaminetetraacetic acid (EDTA) and the samples were named PEG-MoS2 and EDTA-MoS2 respectively. The nanocomposite was synthesized from EDTA-MoS2 and manganese chloride. As synthesized nanostructures and nanocomposite were characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning electron microscope (SEM) equipped with Energy dispersive X-ray spectroscopy (EDS), Transmission Electron Microscope (TEM), and UV-Vis Spectroscopy. Rhodamine B and Methyl Blue were chosen as a model dyes for evaluation of photocatalytic degradation performance. Using PEG-MoS2, the degradation efficiency of 97.30% was achieved for RhB in 75 min and 98.05% for Methyl Blue was achieved in 90 min. EDTA-MoS2 also shows greater potential in the removal of both RhB and MB in aqueous solution; hence 85.46% and 99.78% removals of RhB and MB dyes respectively were achieved in 90 min. PEG-MoS2 nanostructure was also tested for the photocatalytic reduction of Cr(VI) and shows the reduction efficiency of 91.05% in 75 min. The nanocomposite was tested for the photocatalytic degradation of RhB, and results show the degradation efficiency of 98.78% in 75 min. All photocatalytic studies were done under visible light irradiation (Xenon lamp was used throughout).
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Nanozeolite-functionalized poly(lactic acid) ultrafiltration membranes for water treatment
- Authors: Matseke, Mphoma Sophy
- Date: 2016
- Subjects: Water - Purification - Membrane filtration , Membrane filters , Ultrafiltration , Polymeric composites
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/84691 , uj:19252
- Description: Abstract: Water is a scarce resource. This resource deteriorates everyday due to industrial and agricultural activities and other detrimental human activities. Many techniques are already in place for the treatment of drinking water. Membrane technologies have become popular in water treatment in recent times. However, conventional membrane techniques have several drawbacks such as hydrophobicity, low mechanical strength, low chemical reactivity and high propensity of fouling. Ultrafiltration (UF) membranes, in particular, have gained considerable attention in water treatment applications due to their low costs and easy maintenance compared to their counterparts. These membranes utilize known polymer backbones such as polyethersulfone (PES), polysulfone (PSf), and polyvinylfluoride (PVDF). However, the permeabilities for these membranes reduce drastically during water treatment processes. This is due to fouling that occurs on the membrane surface. Membrane fouling is generally caused by adsorption of solutes on the membrane surface and/or the blocking of the membrane pores. Further, UF membranes made from these polymers have low mechanical strength and therefore easily break up when subjected to high pressure systems. This subsequently results in an increase in operating costs and a decrease in overall performance and life-span of the membrane... , M.Sc.
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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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Polyethersulfone (PES) membrane embedded with Fe/Ni nanoparticles decorated-carbon nanotubes (CNTs) for degradation of chlorinated organics in water
- Authors: Thatyana, Maxwell
- Date: 2015-06-30
- Subjects: Water - Purification - Chlorination , Water - Purification - Membrane filtration , Polymeric composites , Nanostructured materials , Carbon nanotubes
- Type: Thesis
- Identifier: uj:13655 , http://hdl.handle.net/10210/13839
- Description: MSc. (Applied Chemistry) , Remediation of POPs particularly the chlorinated compounds in water is therefore crucial. This research work describes the modification of polyethersulfone (PES) thin-film membrane composite (TFC) with functionalised carbon nanotubes (f-CNTs) using the phase invasion method. The oxidised CNTs were successfully decorated with Zero-Valent (ZV) Fe/Ni nanoparticles for the adsorption and degradation studies of polychlorinated organic pollutants (in this case the dichlorodiphenyltrichloroethanes (DDTs)). The in situ modification procedure was carried out using different quantities (0.04 wt%, 0.1 wt% and 0.2 wt%) of Fe/Ni-f-CNTs nanohybrids dispersed in a DMAc solution and dipping the polyethersulfone powder into a suspension containing the Fe/Ni-f-CNTs to form a nano-composite membrane. The formed composite membrane characteristics were investigated with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle (CA) and X-ray diffraction spectroscopy (XRD). The incorporation of nanohybrid in the PES membrane was found to increase the surface smoothness and the hydrophilicity of the composites. In addition, there was an increase in the adsorption of DDTs with increase in the nano-hybrid loading as indicated by the adsorption studies using the Langmuir isotherm and Freundlich isotherm studies. The data obtained from the batch studies closely fitted with the Langmuir isotherm based on the characteristic parameter RL found to lie within the standard range 0 < RL < 1 .
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Polymer composites and nanofiltration membranes and their application in water treatment
- Authors: Dlamini, Derrick Sibusiso
- Date: 2013-07-24
- Subjects: Polymeric composites , Water purification - Membrane filtration
- Type: Thesis
- Identifier: uj:7684 , http://hdl.handle.net/10210/8550
- Description: D.Phil. (Chemistry) , Polycaprolactone (PCL), a linear, biodegradable polymer, and ethylene vinyl acetate (EVA), a branched copolymer, were used to prepare PCNs via the melt-blending method. Organoclay of the type Cloisite® 20A (C20A) and bentonite clay were used as fillers. The results show that the structure of a polymer matrix plays a significant role towards compatibilisation with the silicate layers of the clay. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses revealed an exfoliated-intercalated mixed morphology for the PCL matrix. However, for the EVA matrix, silicate layers agglomerated to form tactoids and resulted primarily in an intercalated morphology. Fourier transform infrared (FT-IR) spectroscopy was used to determine the nature of the interactions between the polymer and the filler. The thermal properties were investigated using thermogravimetric analysis (TGA) and indicated that, with an increase in clay loading, the thermal stability was reduced for both matrices, notwithstanding the type of polymer or clay used. Using EVA and C20A, this study revealed that more exfoliated nanocomposite structures can be obtained by using a modified solution-blending technique. This technique is a hybrid of the melt-blending and solution-blending methods. When compared to the melt-blending method, the modified solution method was found to be an efficient method for producing nanocomposite strips with uniform dispersion of the clay at organoclay loading of 8% and crystallinity by extrusion. However, the melt-blending method produced nanocomposites with high porosity, intercalation and thermal stability whereas the modified solution-blending technique resulted in more intercalated-exfoliated morphology, but less porosity and thermal stability. Despite the positives drawn from the modified solution method, the melt-blending method was used throughout for nanocomposites intended for application in water treatment. This was done because the solution used in the modified solution method could not be completely removed from the nanocomposite. Organic solvents can have a negative effect on the environment and human life.
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Preparation, characterization and properties of polymers based on biocompatible (polyhydroxybutyrate) / polypropylene) blends and nanozeolites towards packaging applications
- Authors: Nkwachukwu, Oluchi Vivian
- Date: 2018
- Subjects: Biodegradable plastics , Polymeric composites , Plastics
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/493474 , uj:45106
- Description: Abstract: Concerns over the persistence of plastics in the environment, this research focuses on the effects of surface modified nanozeolite on polyhydroxybutyrate (PHB) a biodegradable polyester polymer and polypropylene (PP) a non-biodegradable synthetic polymer with a particular interest in the improvement of mechanical, morphological and thermal properties towards packaging products. Surface modified nanozeolite filled PP/PHB composites were prepared in a melt-mixing process and followed by compression molding using hot press machine according to standard test specifications. Nanozeolite was modified through a cationic exchange method using alkyl ammonium ions prior to melt-mixing. The effects of nanozeolite/surface modified nanozeolite loadings of 0.1, 0.25, 0.5, 1.0 wt. % on the properties of 70% PP/ 30% PHB blend composites was studied. Firstly, by characterizing the structure and confirming the functional group on surface modified nanozeolite using x-ray diffraction (XRD), fourier transform infrared radiation spectroscopy-attenuated total reflection (FTIR-ATR). Dynamic mechanical analysis and tensile test were performed to study the mechanical properties of the nanocomposites. Comparative studies on gas barrier properties, biodegradation and antimicrobial activity were conducted. PP/PHB filled with surface modified nanozeolite showed high tensile modulus than unmodified nanocomposites. Thermal properties of all the nanocomposites were evaluated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Results showed that 0.5wt% surface modified nanozeolites is most thermally stable at 400°C while 1wt% surface modified nanozeolite showed fast decomposition rate. PP/PHB blend showed good thermal stabilities at low and high temperature which means poor processability and low thermal stability of PHB has been enhanced by the better properties of PP. Moreover, the morphological study evaluated using SEM revealed fewer cavities and little agglomeration with modified nanocomposites as compared to unmodified nanocomposites which might be an indication of much improved dispersion of modified nanozeolite in the polymer matrix. Surface modified nanozeolite filled composite exhibited improved oxygen and vapour transmission rate, also surface modified nanozeolite composite showed improved weight lost during biodegradation studies. , M.Sc. (Chemistry)
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Preparation/synthesis of electrospun polymer/metal oxide nanocomposite fibers and their application in treatment of brines
- Authors: Ramutshatsha-Makhwedzha, Denga
- Date: 2019
- Subjects: Polymers - Materials , Polymeric composites , Nanocomposites (Materials) , Nanotechnology , Materials science
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/401548 , uj:33565
- Description: Abstract : Many developing countries around the world still lack access to clean fresh water. This refers to water that is free from contaminants as it is highly essential for human livelihood and environment. In countries along the coast, ocean water is the most available water resource; however, it comes at a salt concentration that is very high for human consumption. Most of available water has a salinity of up to 10 000 ppm and seawater consists of dissolved salt concentrations of about 35 000-45 000 ppm. This lead to desalination process being used as an option to treat seawater and this has become one of the most important processes of providing fresh water in developing countries. Therefore, the aim of this study was to investigate the practicability of using nanometer metal oxides and polymer/NMO composite as the potential adsorbents for adsorption desalination of seawater. The quantification of analytes in sample solutions was done using the inductively-coupled plasma atomic emission spectroscopy (ICP-OES). Nanometal oxide composites such as Fe2O3-SiO2, SiO2/Nb2O5/Fe2O3, Fe2O3-SiO2-PAN and zeolite/Fe3O4 adsorbents were used for the adsorptive desalination of saline water. Fe2O3-SiO2, SiO2/Nb2O5/Fe2O3 and zeolite/Fe3O4 adsorbents were prepared using a sol gel method whereas Fe2O3-SiO2-PAN nanocomposite was obtained using in-situ preparation method. The adsorbents were characterized using different techniques such as scanning electron microscopy (SEM), x-ray diffraction (XRD), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET). SEM image of Fe2O3-SiO2 nano composite showed the porous morphological structure. The Fe2O3-SiO2 showed partial crystalline pattern due to silica oxide that has pure amorphous structure, whereas the SiO2/Nb2O5/Fe2O3 has an amorphous structure. TEM structure of α-Fe2O3 has dominant shapes of spherical and some few cubic and hexagonal shapes, the hexagonal shape were also observed on Fe2O3-SiO2 nanocomposite material. SiO2/Nb2O5/Fe2O3 adsorbent resembled a core-like structure. The TEM result of Fe2O3-SiO2-PAN revealed that the crystalline Fe3O4 nanoparticles were encapsulated with PAN polymer that suggests the core-shell structure. EDX-mapping analysis showed the uniform elemental distribution which suggests the successful preparation of the in-situ method... , Ph.D. (Chemistry)
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Synthesis and characterization of polymer and carbonaceous nanocomposites and their application in hydrostatic pressure sensing
- Authors: Mofokeng, Lethula Excellent
- Date: 2017
- Subjects: Carbon composites , Nanocomposites (Materials) , Nanostructured materials , Polymeric composites
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/244052 , uj:25235
- Description: M.Sc. (Nanoscience) , Abstract: Flexible polymer nanocomposites thin films holds promising applications in electronics and are good candidates for pressure sensing and other technological applications due to their flexibility and other novel properties they exhibits. Carbonaceous nanomaterial polymer nanocomposites were utilized to fabricate pressure sensors via a simple and cost- effective process of non-covalent functionalization. We successfully managed to demonstrate the use of cheap, stable, thermoplastic polymers for producing thin films for pressure sensing applications and applicable also for future electronic devices applications. The use of CNPs gave better resistive and capacitive sensing application with response times ranging from 3 to 11 seconds and operate effective for a wide dynamic range (56 to 190 kPa) for both resistive and capacitive sensing compared to O-MWCNTs. The sensitivities of carbonaceous nanomaterials are dependent on the nature of the polymer, loadings of polymer ratios (1:1, 1:2, 1:3, 2:1, 2:2, 2:3, 3:1, 3:2 and 3:3) and percolation threshold. CNPs/PAN pressure sensor was measured for electrical resistance and capacitance pressure sensing. The CNPs/PAN was the highest sensitivity resistive pressure sensor than any other in relation to O-MWCNTs and rGO – based pressure sensors having 5.12 kPa-1. CNPs/PAN took three second to reach 90% pressure stimuli response time and also it took in three seconds for 90 % recovery time to retain its initial state at Ro under applied pressure with linear range from 56 to 190 kPa. Capacitive sensitivity was 1.33 kPa-1 for CNPs and CA thin film pressure sensor exhibiting linearity with a wide dynamic range and reversible behaviour. When Fe3O4 was incorporated to CNPs and CA, low sensitivities for resistive and capacitive pressure sensing were obtained for CNPs/Fe3O4/CA. Resistive sensitivity was 2.08 x 10-6 kPa-1 and 0.04 kPa-1 for capacitive sensitivities. This implies that, Fe3O4 had a huge impact on the structure, arrangement, uniformity, distribution and conducting channels within the polymer nanocomposites. As for O-MWCNTs and rGO –based pressure sensors, similar reduction in sensitivities due to Fe3O4...
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Synthesis and modifications of polymer-based carbon/metal organic framework composites for hydrogen storage applications
- Authors: Molefe, Lerato
- Date: 2019
- Subjects: Polymeric composites , Carbon nanotubes , Carbon composites , Nanocomposites (Materials)
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/417836 , uj:35402
- Description: Abstract: The South African energy landscape is dominated by carbon dioxide (CO2) emitting coal combustion which is currently plentiful and cheap however because of its finite nature, it will soon diminish. With the current growing population and increasing energy need, research scientists all over the world are continuously working towards shifting to cleaner renewable energy sources of which hydrogen (H2) is a promising candidate. Hydrogen has a high gravimetric energy density than any other fuel and its combustion in pure oxygen only produces water vapour and heat. However, since it is very light and as a result has a low volumetric energy density, its storage is very difficult. Generally, adsorbents materials such as metal-organic frameworks (MOFs) such as Materials Institute Lavoisier (MIL-101(Cr)) and Universitetet i Oslo (UiO-66(Zr)) as well as porous carbons such as zeolite templated carbon (ZTC) have been well investigated for H2 storage due to their unique properties such as extremely high surface areas and ultrahigh porosities. However, their great potential in H2 storage applications is limited by their lack of immediate processability, because they are obtained as fine powders in their as-synthesised form. For these materials to gain practical applications in H2 storage they must be shaped into mechanically stable and easy to handle bodies like monoliths. The process of shaping MOFs and carbon powders often includes the use of various non-porous polymers and inorganic materials as binders and that often results in pore-blocking effects and low H2 uptake... , Ph.D. (Chemistry)
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The fabrication of polymer nanocomposite based sensors for the detection of ethanol, methanol and hydrogen sulphide, produced during beer fermentation
- Authors: Olifant, Goitsione Emily
- Date: 2018
- Subjects: Beer - Analysis , Polymeric composites , Nanocomposites (Materials)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/493194 , uj:45072
- Description: Abstract: Gas sensing technology is a subject that is increasingly being studied and becoming more applicable in areas such as fermentation, personal safety, academic research and many others. This study includes different types of sensors. This research focused on gas sensors, specifically volatile organic compounds sensors. Volatile organic compounds are applicable in many production areas such as alcoholic beverage production. Beer is the most produced alcoholic beverage worldwide and the three main volatile organic compounds applicable to the production of beer are Ethanol, Methanol, and Hydrogen sulphide which contribute majorly to the mouth feel, flavour and the odour of beer. During beer fermentation, these three compounds require constant monitoring to avoid being over produced and contamination. Currently, the detection of Ethanol, Methanol, and H2S are undertaken by conventional methods such as high-liquid-performance chromatography, gas chromatography, and near-infrared spectroscopy. These methods are time-consuming. They lack portability and are very expensive... , M.Tech. (Biotechnology)
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