As the clothing industry moves away from traditional models of mass production there has been increased interest towards customised clothing. The technology to produce cost effective customised clothing is already in place however the prerequisite to customised clothing is accurate body dimensional data. In response, image capture systems have been developed which are capable of recording a three-dimensional image of the body, from which measurements and shape information may be extracted. The use of these systems for customised clothing has, to date, been limited due to issues of inaccuracy, cost and portability. To address the issue of inaccuracy a diagnostic procedure has been developed through the performance evaluation of an image capture system. By systematically evaluating physical and instrumental parameters the more relevant sources of potential error were identified and quantified and subsequently corrected to form a `closed loop' experimental procedure. A systematic test procedure is therefore presented which may be universally applied to image capture systems working on the same principle. The methodology was based upon the isolation and subsequent testing of variables that were thought to be potential sources of error. The process therefore included altering the physical parameters of the target object in relation to the image capture system and amending the configuration and calibration settings within the system. From the evaluation the most relevant sources of error were identified as the cosine effect, measurement point displacement, the dimensional differences between views and the influence of the operator in measurement. The test procedure proved to be effective in both evaluating the performance of the system under investigation and in enabling the quantification of errors. Both random and systematic errors were noted which may be quantified or corrected to enable improved accuracy in the measured results. Recommendations have been made for the improvement of the performance of the current image capture system these include the integration of a cosine effect correction algorithm and suggestions for the automation of the image alignment process. The limitations of the system such as its reliance on manual intervention for both the measurement and stitching processes, are discussed, as is its suitability for providing dimensional information for bespoke clothing production. Recommendations are also made for the creation of an automated test procedure for testing the performance of alternative image capture systems, which involves evaluating the accuracy of object replication both for multiple and single image capture units using calibration objects which combine a range of surfaces.

This investigation examines the structure-property relationships of high modulus fibres. Five fibre classes were chosen for examination. These are p-aromatic copolyamide (Armos and SVM) and poly-p-aramids (Terlon and Kevlar) obtained from rigid chain polymers; poly-m-aramids (Phenylon and Nomex) obtained from semi rigid chain polymers, and aliphatic polyamide (Capron and Nylon) and Polyethylene obtained from flexible chain polymers. The thermo-mechanical properties studied include tensile properties, thermal shrinkage, creep-recovery, stress-relaxation and residual deformation over a range of temperatures. Results show that mechanical properties are highly related to chain rigidity, orientation and crystallinity of the fibres. The presence of aromatic rings in polymer chains increase the polymer rigidity. The higher the intermolecular attractive force and chain rigidity, the greater the resistance to heat. Study of the creep-recovery properties of polyamide fibres shows that irrecoverable residual deformation for the rigid chain polymers is accumulated within a very short initial period of time (15 seconds) when the load is applied. However for semi-rigid or flexible chain polymer fibres, the residual deformation is accumulated during the whole creep process. The characteristics of tensile stress-strain properties and the accumulation of residual deformation are found to be temperature dependent, especially in the case of Armos and SVM. The mechanical properties of polyamide fibres are also influenced by moisture which is associated with intermolecular interaction. Supplementary studies using FTIR, SEM and DSC were also undertaken. FTIR was used for preliminary investigation into the intermolecular hydrogen bonding and associated moisture in fibres. The results support the explanation of the thermomechanical properties of polyamide fibres. SEM results show the fibre rupture mechanism related to the fibre structures.

Betulin is a naturally abundant compound in the outer bark of birch and can be easily obtained by solvent extraction. Herein, solutions of betulin were used to treat cellulosic textile fibers and improve their water repellency. Cotton fabrics impregnated in a 7.5 g L-1 solution of betulin in ethanol showed the highest water contact angle of about 153° while the impregnation in a 3.75 g L-1 solution resulted in a close effect. A terephthaloyl chloride-betulin copolymer was synthesized and dissolved in tetrahydrofuran to afford a solution with a concentration of 3.75 g L-1. The cotton fabric impregnated in this solution showed a water contact angle of 150°. Changes in morphology of the cellulose fibers before and after the treatment were observed by scanning electron microscopy, and the water repellency was measured by a standard spray test. The marketing strategy of the potential product, which will be developed based on this technique, was discussed.

Thesis (MSc (Physics))--University of Stellenbosch, 2009. / The role fulfilled by theoretical models is rapidly increasing due to lasers becoming appli- cation driven to satisfy certain criteria and demands. Construction of high precision lasers requires good theoretical models and consequently good approximations of the parameters that such models are based upon. Despite the di erent model formalisms, most share a com- mon set of input parameters, including fibre waveguiding properties, input powers, transition cross-sections and overlaps between guided modes and the dopand distribution. Experimental and numerical work which was aimed at obtaining the wide-band emission and absorption cross-sections of fibre indirectly by means of the Giles parameters was done. The Giles parameters were used rather than the well known ionic cross-sections primarily because of the convenient encapsulation of the cumbersome overlap factors and the ionic cross-sections within the Giles parameters. The wide band spectral characteristics of the Giles parameters are indispensable in the design of fibre lasers and amplifiers, as they form the key parameters for laser models. These parameters are normally obtained utilizing absorption spectroscopy to obtain the absorption cross-sections and models such as the Fuchtbauer Ladenberg relation, the Mc- Cumber relation or uorescence spectroscopy to obtain the emission cross-sections. Recent research however indicates that these methods are inaccurate in certain spectral regions. An investigation was launched to extract the Giles parameters from measurements of the ampli- fied spontaneous emission (ASE) and pump absorption in ytterbium-doped fibre for several lengths of fibre and subsequent computer simulations, utilizing an ampli fier model. The Giles parameters are extracted with a fitting algorithm that adjusts the relevant numerical values to minimize the least square difference between the numerical data obtained from the amplifier model and the measured data. Using the model devised in this project on literature data, the Giles parameters were extracted and compared to the Giles parameters extracted in literature on the same data. This comparison conforms the extraction of the Giles parameters, utilizing the model devised in this project, as successful. Subsequently the model devised in this project was applied to extract the Giles parameters from experimental data measured at Stellenbosch, using a double cladding ytterbium-doped fibre. Finally a fibre laser was built utilizing the double cladding ytterbium-doped fibre and the output was measured. The Giles parameters extracted were then used in a fibre laser model to calculate the output and compare it to the measurements taken. This served as suffcient verification that the Giles parameters extracted can be used to model a fibre laser effciently.

Thesis (MSc)--University of Stellenbosch, 2011. / Please refer to full text to view abstract.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2009. / The study concerns the use of the electrospinning technique for the formation of cellulose acetate hollow nanofibers. These hollow fibers are used to manufacture hollow fiber membranes. Important properties that should be inherent to these hollow-nanofibers include excellent permeability and separation characteristics, and long useful life. They have potential applications in filtration, reverse osmosis, and the separation of liquids and gases. It is apparent from the available literature on electrospinning and co-electrospinning that the diameter and the morphology of the resulting fibers are significantly influenced by variations in the system and process parameters, which include the solution concentration, solvent volatility, solution viscosity, surface tension and the conductivity of the spinning solution. The materials used include cellulose acetate (CA) (concentration = 11~14 wt %), (feed rate = 1~3 ml/h), acetone:dioxane (2:1) and mineral oil (feed rate = 0.5~1 ml/h) with core and shell linear velocity of 2 and 0.7 mm/min respectively. These materials were used as received without further purification. The co-electrospinning setup used comprised a compound spinneret, consisting of two concentric small-diameter capillary tubes/needles, one located inside another (core-shell/co-axial design). The internal and external diameters of the inside and outside needles were 0.3 and 1.2 mm respectively (0.3 mm shell/core gap space). The liquids CA (shell) and mineral oil (core) are pumped to the coaxial needle by a syringe pump, forming a compound droplet at the tip of the needle. A high voltage source is used to apply a potential of several kilovolts over the electrospinning distance. One electrode is placed into the spinning solution and the other oppositely charged (or neutral) electrode attached to a conductive collector. If the charge build up reaches approximately 15 kV the charged compound droplet, (poorly conductive polymer solution) deforms into a conical structure called a Taylor cone. On further increasing, the charge at the Taylor cone to some critical value (unique to each polymer system) the surface tension of the compound Taylor cone is broken and a core-shell jet of polymer solution ejects from the apex of the Taylor cone. This jet is linear over a small distance, and then deviates in a course of violent whipping from bending instabilities brought about by repulsive charges existing along the jet length. The core-shell jet is stretched and solvent is evaporated and expelled, resulting in the thinning and alignment of the fiber. Ultimately dry (most solvent having been removed) submicron fibers are collected in alignment form in a simple collector design (water bath). The shell to core solution flow rate ratio was chosen according to the parameter response of shell-core diameter of the resulting fibers in order to achieve an optimal hollow structure after removal of the mineral oil core. The mineral oil of the dry collected core-shell fibers is removed by immersion in octane. The aforementioned response is determined by measurement of core-shell diameters using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The obtained results showed that the ability of the spinning solution to be electrospun was directly dependent on its concentration and the feed rate of the spinning solution and also parameters such as the spinning distance and type of solvents used. The preferable polymer solution concentration is 14 wt %, shell feed rate of 3 ml/hr, core feed rate of 0.5 ml/hr (2 and 0.7 mm/s core and shell linear velocity respectively), applied voltage of 15 KV, spinning distance of 8 cm and coaxial spinnerets having internal diameters of 0.3 mm and 1.2 mm core and shell needles respectively (0.3 mm shell/core gap space) have been found to make uniform cellulose acetate hollow fibers with an average inside and outside diameter of approximately 495 and 1266 nm, respectively.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006. / Rectangular components were produced by both standard injection moulding and by a process called Lomolding. Both moulding grade polypropylene homopolymer and glass-filled polypropylene were used. The effect of processing parameters on material properties, as measured by tensile and impact strength, and warpage were determined for both injection moulding and lomolding, for both unfilled and glass-filled polypropylene materials. Sampling of the components allowed for critical evaluation of processing parameters’ effect on material properties at points close to and distant from the injection point, as well as in the direction of materials flow and transverse to material flow. Glass-filled components were also evaluated in terms of glass fibre length and fibre distribution (post-injection). Overall conclusions could be drawn with respect to the 2 different processes and the materials used. It was seen, inter alia, that the specimen orientation had no effect on the mechanical properties when using unfilled polypropylene, but that the orientation of the glass fibres in the testing direction resulted in an increase in the tensile strength and the impact strength for the injection moulded samples. Similar results were seen for lomolded samples, except that the fibre orientation effects were different. In the same vein, other notable differences could be observed for samples produced by lomolding and injection molding. Fibre length and distributions obtained by polymer burn-off experiments served to help explain differences in properties of glass-filled products produced by the two processes.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2009. / In papermaking, the addition of filler can be detrimental to the properties of the resulting paper hence the use of additives that enhance paper properties are of paramount importance. Syndiotacticity rich poly(vinyl alcohol) (PVA) microfibrils were prepared for use as filler retention aids. They were prepared via in situ fibrillation during the saponification of high molecular weight poly(vinyl pivalate). The resulting fibers had high thermal stability and crystalline melting temperature. They were not fully soluble in water even at 100 oC. In order to make them less water resistant the syndiotacticity of the PVA microfibrils was varied by copolymerizing vinyl pivalate with vinyl acetate and saponifying the resultant copolymer. It was observed that changes in syndiotacticity had a significant effect on the crystallinity, morphology and thermal properties of the resultant PVA. The surfaces of the fibers were modified by first crosslinking using glyoxal (a dialdehyde), and then attaching cationic and anionic groups by grafting and by carboxymethylation. Crosslinking prior to modification was beneficial in minimizing the solubility of the fibers in the aqueous media in which they were modified. Heterogeneous modification techniques were employed so that fiber properties could be preserved. Carboxymethylation was carried out using the two step Williamson’s ether synthesis. The first step involves the formation of a highly reactive alkoxide by the reaction of PVA with a strong base and the second its etherification using a functional alkyl halide. Poly(methacryloyloxy ethyl trimethyl ammonium chloride) and poly(acrylic acid) were grafted from the PVA microfibrils using the KPS/Na2S2O3 redox initiation system. Grafting was confirmed by FTIR and NMR spectroscopy. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were carried out on both modified and unmodified PVA microfibrils. The results showed that crosslinking resulted in an enhancement of the thermal properties of the microfibrils. A decline in the onset temperature for thermal degradation and crystalline melting temperature were observed, and were attributed to the modification of the PVA microfibrils.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009. / The PBMR has called for research into the possibility of distributed in-core temperature measurement. In this thesis, several methods for distributed temperature measurement in high-pressure, -radiation and -temperature environments have been investigated by means of a literature study. The literature study has revealed FBG temperature sensors as the most feasible solution to the temperature measurement challenge. Various parameters affecting the propagation of light in optical fibres and consequently the FBG reflection profile was researched. The differential equations describing FBG structures were solved and implemented in Matlab in order to simulate WDM of a distributed FBG sensing system. Distributed sensing with apodized FBGs written in sapphire optical fibre show the most promise of becoming a solution to the measurement challenge. However, practical testing of sapphire FBGs exposed to the environment in the PBMR core is required. With this long-term goal in mind, a general test platform for FBG temperature sensors was assembled. A heater controller was built for a specialized fibre heating element capable of controlling the temperature of a single FBG up to 1600 C. Temperature measurement using wavelength division multiplexing of apodized FBGs written in silica optical fibre were demonstrated in the test platform with great success. The measured results corresponded very well with the theory. Finally, the implementation of FBGs in the PBMR is discussed and recommendations are made for future work

published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy