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In this study the potential use of thermochromic colorants in swimwear garments was investigated and the effectiveness of a colour transition in and out of water as a result of changes in temperature assessed. This project considers the use of thermochromic colorants for end use application in Speedo brand swimsuits for women and the opportunity for producing multiple colour transitions or even changes in design pattern. Prior to the application of thermochromic colorants to swimwear, a number of factors must be considered, most importantly, the colorimetric properties and fastness properties of thermochromic colorants applied to the textiles. Currently there is limited information available relating to the colorimetric and fastness properties of thermochromic colorants, particularly where applied to textile substrates. A novel colour measurement methodology suitable for the dynamic colour measurement of thermochromic colorants applied to textiles was developed. Investigations showed that thermochromic colorants exhibited different rates of decolourisation and re-colourisation as well as varying colorimetric behaviour depending on the maximum exposure temperature. The developed colour measurement methodology was used to investigate the fastness properties of thermochromic colorants applied to a polyamide/elastane swimwear fabric. The test samples were found to have varying wash fastness properties depending on the colour of the thermochromic colorant. Furthermore, samples were found to have unsatisfactory fastness to a simulated sunlight (xenon arc light source). However, it was found that by removing specific wavelengths of visible light, using a filter, the rate of degradation was reduced. Rub fastness properties in the dry state were acceptable, though loss of the thermochromic colorants was observed in the wet state. Exposure to chlorinated water adversely affected the test samples causing yellowing, particularly in the thermochromic decolourised state. Thermography and pressure testing techniques were employed in order to identify the areas of Speedo swimsuits most suitable for the placement of thermochromic print motifs. Garment pressure test results showed that the shape of a swimsuit and the fabric from which it was made was found to impact the fit. Thermography testing identified that the fit of a swimsuit had an effect on the convection of heat from the body to the swimsuit. The test results also showed that temperature distribution varied depending on the distribution of muscle and fat on the body. Thermochromic colorants were screen printed on to digitally printed ground substrates to investigate the colour transition effects achievable. Due to the translucency of thermochromic colorants colour mixing with the colour of the ground substrate occurred in the thermochromic coloured state. Print motifs suitable for use in Speedo swimwear were developed and conceptual diagrams showing dynamic thermochromic placement prints for swimwear were created.

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With regard to the recent interests in smart textiles,this research activity has been conducted with the aim of producing a pattern changing design on textiles. In order to fulfill the demands of such dynamic patterns a combinationof conductive polymer and thermochromic pigments wereused. The textile substrate was coated by conductive polymer dispersion(PEDOT:PSS) and it was followed with printing thermochromic pigments on the surface of coating.The driving force of such thermochromic reaction has to be provided by the heat generated from conductive layer dueto the current of electricity passing through the conductivelayer. These experiments were continued by changing thecoating recipe in order to achieve the highest possible electrical resistance,which leads to the best initiation ofthermochromic reactions. / Program: Master programme in Textile Technology

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Metamaterials are engineered periodic composites that have unique refractive-index characteristics not available in natural materials. They have been demonstrated over a large portion of the electromagnetic spectrum, from visible to radiofrequency. For applications in the infrared, the structure of metamaterials is generally defined using electron-beam lithography. At these frequencies, the loss and dispersion of any metal included in the composite are of particular significance. In this regard, we investigate deviations from the Drude model due to the anomalous skin effect. For comparison with theoretical predictions, the optical properties of several different metals are measured, both at room temperature and at 4 K. We extend this analysis to the coupling between plasmon and phonon modes in a metamaterial, demonstrating that very thin oxide layers residing at the metal-substrate interface will significantly affect the spectral location of the overall resonance. Oxide-thickness-dependent trends are then explored in some detail. Potential applications of this general area of study include surface-enhanced infrared spectroscopy for chemical sensing, and development of narrowband notch filters in the very long wavelength infrared. We then consider various possibilities for development of tunable infrared metamaterials. These would have wide applicability in dynamically variable reflectance surfaces and in beam steering. We consider several methods that have been previously shown to produce tunable metamaterials in the radio frequency band, and explore the challenges that occur when such techniques are attempted at infrared frequencies. A significant advance in tunable-infrared-metamaterial technology is then demonstrated with the use of thermochromic vanadium dioxide thin films. Highlights include the first demonstration of a tunable reflectarray in the infrared for active modulation of reflected phase, the first demonstration of a tunable resonance frequency in the thermal infrared band, and the largest resonance-frequency shift recorded to date in any part of the infrared. Finally, future work is proposed that holds the promise of wideband frequency tuning and electronically-controllable metamaterials.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2009. / Thesis presented in partial fulfilment of the requirements for the degree of Master of Science (polymer science) at the University of Stellenbosch / Embargo date 2010-03-31 plt 2010 / ENGLISH ABSTRACT: A novel method, herein referred to as ‘solvent facilitated coaxial electrospinning’, was used to produce reversibly thermochromic core-shell fibres with poly(methyl methacrylate) (PMMA) as shell and a thermochromic dye composite as core. The thermochromic dye composite consisted of combinations of 1-dodecanol, bisphenol A (BPA) and crystal violet lactone (CVL). In the ‘solvent facilitated coaxial electrospinning’ method, the thermochromic dye composite was dissolved in a suitable ‘facilitating solvent’ prior to spinning, instead of being spun into the fibres from the melt as previously described in literature. A low interfacial tension between the core and shell liquids, which is beneficial to effective core entrainment, was achieved by using a correctly chosen core ‘facilitating solvent’. The PMMA was dissolved to form the shell spinning liquid and by selecting the correct core and shell solvents, spinneret blockage and precipitation due to core and shell liquid interactions were eliminated. High molar mass PMMA was used to produce fibres with diameters in the range of 3–10 μm (larger than typical electrospun fibres) in order to minimize light scattering and subsequently allow visual observation of the thermochromic transitions, unlike the fibres that were produced in literature. The fibres were analyzed using SEM, TEM, TGA and DSC to investigate fibre morphology, dye composite thermal transition and fibre composition. Physical and chemical interactions between the thermochromic dye composite and the PMMA shell were identified as possible causes of differences between the thermochromic transition temperatures of the core-shell fibres and the bulk dyes, as well as of the instability of the colour developed state of certain thermochromic fibres. The spatial confinement of the dye composite inside the fibres and the extensive volume reduction (from bulk dye to small volume inside the fibres) affected the thermochromic behaviour of the thermochromic composite once it was entrained in the fibres. An excess BPA was used in the dye composition to allow the production of reversibly thermochromic fibres with a stable colour developed state. / AFRIKAANSE OPSOMMING: A nuwe metode, hierin beskryf as ‘oplosmiddel gefasiliteerde koaksiale elektrospinnery’, is gebruik om omkeerbare termochromiese kern-skil vesels met polie(metiel metakrilaat) (PMMA) as skil en ‘n saamgestelde termochromiese kleurmiddel as kern te vervaardig. Die saamgestelde termochromiese kleurmiddel het bestaan uit kombinasies van 1-dodekanol, bisfenol A (BPA) en kristal violet laktoon (CVL). Vir die ‘oplosmiddel gefasiliteerde koaksiale elektrospin’-metode, is die saamgestelde termochromiese kleurmiddel opgelos in ‘n gepaste ‘fasiliterende oplosmiddel’ voordat dit geëlektrospin is, eerder as om dit te smelt om dit sodoende in vesels te kan inspin soos beskryf in die literatuur. ‘n Lae raakvlakspanning tussen die kern- en skilspinvloeistowwe, wat voordelig is vir doeltreffende kern insluiting, is bereik deur gebruik te maak van sorgvuldig verkose ‘fasiliterende oplosmiddels’ vir die kern. Die PMMA is opgelos om die skilspinoplossing te vorm en, deur die keuse van die korrekte kern- en skiloplosmiddels, kon spinneret blokkasie en neerslag van die polimeer as gevolg van kern- en skilvloeistofinteraksies elimineer word. Hoë molekulêre massa PMMA is gebruik om vesels te vervaardig met deursnee in die omtrek van 3–10 μm (groter as tipiese elektrogespinde vesels) om sodoende lig-verstrooiing te verminder en daardeur visuele waarneming van die termochromiese oorgange moontlik te maak, in teenstelling met die vesels wat in die literatuur gevorm is. Die vesels is ge-analiseer met SEM, TEM, TGA en DSC om veselmorfologie, termiese omskakelinge van saamgestelde kleurmiddels en veselsamestelling te bestudeer. Fisiese en chemiese interaksies tussen die saamgestelde termochromiese kleurmiddel kern en die PMMA skil is geïdentifiseer as moontlike oorsake van verskille tussen die termochromiese oorgangstemperature van die kern-skil vesels en die kleurmiddels in grootmaat, asook van die onstabiliteit van die gekleurde toestand van sommige termochromiese vesels. Die ruimtelike inperking van die saamgestelde kleurmiddel binne in die vesels asook die beduidende volume verkleining (van grootmaat kleurmiddel tot klein volume binne in die vesels) het die termochromiese gedrag van die saamgestelde kleurmiddel binne die vesels beïnvloed. ‘n Oormaat BPA is in die saamgestelde termochromiese kleurmiddel gebruik om die produksie van omkeerbaar termochromiese vesels met ‘n stabiele gekleurde toestand toe te laat.

With the technological progress of materials science, the palette of colours with which to print on textiles has expanded beyond those with previously known properties and expressions to a new generation, with more advanced functionality and expressive properties. This new range of colours is characterised by their ability when printed on textiles to change colour in relation to external factors and internal programmes; for example, leuco dye-based thermochromic inks generally change colour in response to temperature fluctuations. This research explores the design properties and potentials of leuco dye-based thermochromic inks printed on textiles, with regard to creating a wider range of colour-changing effects for textile applications. The significance of this for textile design is related to the development of a methodology for designing dynamic surface patterns. The research was conducted by creating a series of design experiments using leuco dye-based thermochromic inks, which resulted in different recipes and methods, along with a pedagogical tool. The results highlighted the diverse colour-changing properties of leuco dye-based thermochromic inks, which have the potential to create more complex patterns on textiles. The outcome of this research proposes a foundation for textile designers with which to approach new ways of thinking and designing.

<p>In modern gas turbines parts of combustion chamber and turbine section are under heavy heat load, for example, the rotor inlet temperature is far higher than the melting point of the rotor blade material. These high temperatures causes thermal stresses in the material, therefore it is very important to cool the components for safe operation and to achieve desired component life. But on the other hand the cooling reduces the turbine efficiency, for that reason it is vital to understand and optimize the cooling technique.</p><p>In this project Thermochromic Liquid Crystals (TLCs) are used to measure distribution of heat transfer coefficient over a scaled up combustor liner section. TLCs change their color with the variation of temperature in a particular temperature range. The color-temperature change relation of a TLC is sharp and precise; therefore TLCs are used to measure surface temperature by painting the TLC over a test surface. This method is called Liquid Crystal Thermography (LCT). LCT is getting popular in industry due to its high-resolution results, repeatability and ease of use.</p><p>Test model in present study consists of two plates, target plate and impingement plate. Cooling of the target plate is achieved by impingement of air coming through holes in the impingement plate. The downstream surface of the impingement plate is then cooled by cross flow and re-impingement of the coolant air.</p><p>Heat transfer on the target plate is not uniform; areas under the jet which are called stagnation points have high heat transfer as compare to the areas away from the center of jet. It is almost the same situation for the impingement plate but the location of stagnation point is different. A transient technique is used to measure this non-uniform heat transfer distribution. It is assumed that the plates are semi-infinitely thick and there is no lateral heat transfer in the plates. To fulfill the assumptions a calculated time limit is followed and the test plates are made of Plexiglas which has very low thermal conductivity.</p><p>The transient technique requires a step-change in the mainstream temperature of the test section. However, in practical a delayed increase in mainstream temperature is attained. This issue is dealt by applying Duhamel’s theorem on the step-change heat transfer equation. MATLAB is used to get the Hue data of the recorded video frames and calculate the time taken for each pixel to reach a predefined surface temperature. Having all temperatures and time values the heat transfer equation is iteratively solved to get the value of heat transfer coefficient of each and every pixel of the test surface.</p><p>In total fifteen tests are conducted with different Reynolds number and different jet-to-target plate distances. It is concluded that for both the target and impingement plates, a high Reynolds number provides better overall heat transfer and increase in jet-to-target distance</p><p>decreases the overall heat transfer.</p>