The aim of the research was to produce hollow yarn knitted fabrics with improved thermal comfort properties. Thermal comfort properties and utility properties determine the wearing comfort of textiles and the suitability of a new textile product for a particular application. Both, Thermal comfort properties such as thermal absorptiveness, thermal conductivity, air permeability and utility properties like percent stretch, spirality, bursting strength of core yarn knitted fabrics and hollow yarn knitted fabrics were assessed. A new method was proposed and discussed for producing hollow yarns at fabric stage (in this case knitted fabric) which involved the following steps: - a) Production of ring spun yarns, comprising nylon as a core and cotton as a sheath, using Ring Spinning System. b) Production of knitted fabrics of different knit structures viz., single jersey, rib and interlock using above mentioned yarn. c) Dissolution of core element i.e. Nylon into formic acid to obtain hollow yarn knitted fabrics and this hollow yarn knitted fabrics can be tailored for specific end use. The study covers comparative analysis of thermal insulation properties like thermal absorptiveness, thermal conductivity and others for core yarn knitted fabrics and hollow yarn knitted fabrics and the influence of the count of core nylon filament and the type of knit structures on the thermal properties of the fabrics. Based on the results obtained from the work, it can be stated that hollow yarn knitted fabrics offer numerous possibilities for creating fabric properties which influence their comfort of use.

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Orientador: Rubens Maciel Filho / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-25T09:22:08Z (GMT). No. of bitstreams: 1 Oliveira_HerbertPereirade_D.pdf: 4267666 bytes, checksum: ab495e80bdcc1edbfd0e338de9888c01 (MD5) Previous issue date: 2013 / Resumo: Este trabalho teve como objetivo principal a proposta de projeto de uma planta piloto de polimerização Nylon 6 para o desenvolvimento de novas aplicações. O processo adotado é a polimerização hidrolítica do Nylon 6, a partir do monômero ?-caprolactama, que compreende a vaporização de ambos, monômero e água, em um reator de bancada operado no regime de batelada. O Nylon 6 vem sendo produzido no Brasil quase que exclusivamente para emprego no setor de fibras, mas outras aplicações aumentariam o consumo deste polímero. Assim, o desenvolvimento de Nylon 6 para outros fins, como por exemplo no setor de plásticos de engenharia (eletrodomésticos e setor automotivo) é necessário para diversificar o seu consumo, direcionando-o a novos mercados, como forma de garantir a sua permanência e utilização neste setor altamente competitivo, que é o setor de plásticos como um todo, no qual, em face da globalização, os diversos produtos passam a competir nos mais diversos campos de aplicação. Este trabalho compreendeu o projeto conceitual, detalhamento de projeto, desenvolvimento, construção, montagem e definição de procedimentos experimentais da planta piloto, de modo a reproduzir, em escala piloto, as condições do processo industrial de polimerização em batelada. Concluída a etapa de projeto, construção e montagem, e comissionamento da planta, foram realizados testes pré-operacionais, com análise e correção dos problemas verificados. Foram realizadas duas corridas experimentais e as amostras do polímero obtido foram caracterizadas e comparadas às amostras padrões fornecidas por indústrias locais. A planta desenvolvida se mostrou operacional e flexível para o desenvolvimento de Nylon 6 com características controladas, o que é necessário para as possíveis aplicações como plástico de engenharia / Abstract: This investigation aimed to propose the design of a Nylon 6 pilot plant polymerization for the development of new applications. The process adopted is the hydrolytic polymerization of nylon 6 from epsilon-caprolactam monomer comprising vaporization of both, monomer and water, in a batch operated reactor. The Nylon 6 has been produced in Brazil almost exclusively for fiber sector employment, and new applications are welcome to increase the production of such polymer. Thus, the development of Nylon 6 for other purposes, such as in engineering plastics sector (appliances and automotive) is necessary to diversify their consumption, directing you to new markets as a way to ensure its permanence and use this highly competitive industry, which is the plastics industry as a whole, which, in the face of globalization, the products are competing in various application fields. This research work comprised the proposal of a conceptual design, detailed design, development, construction, installation and definition of experimental procedures of a pilot plant, for Nylon 6 polymerization, in order to be able to reproduce in a pilot plant scale, industrial process conditions in batch polymerization. After the design phase, construction, assembly, and plant commissioning, pre-operational tests were performed, with analysis of the results and correction of detected problems. Two experimental runs were performed and samples of the polymer obtained were characterized and compared with standard samples supplied by local industries. The pilot plant proved to be and operational with a good degree of flexibility to the development of Nylon 6 with controlled characteristics, which is necessary for the potential applications as engineering plastics / Doutorado / Desenvolvimento de Processos Químicos / Doutor em Engenharia Química

This dissertation investigates the fundamental behavior of multifunctional materials for energy conversion. Multifunctional materials exhibit two or more functional properties, such as electrical, thermal, magnetic etc. In this dissertation, the emphasis is on understanding the principles for energy conversion from one domain to another (e.g. thermal to electrical; or mechanical to electrical) by utilizing nanomaterials and nanostructured materials such as carbon nanotubes, shape memory alloy (SMA), and flexible piezoelectric materials. Carbon nanotubes (CNTs) are known for their unique electrical and thermal properties. Development of solid-state suspended CNT sheets having extremely low heat capacity per unit area opens an opportunity for utilizing thermoacoustic phenomenon (electrical to thermal to acoustic energy conversion) that results in sound generation over a wide range of frequencies. Detailed theoretical modeling and experiments were conducted for understanding the acoustics generation from multi-wall carbon nanotubes (MWNTs) sheets. The sound pressure level (SPL) of CNT-based thermoacoustic projector (TAPs) is proportional to the frequency and hence the performance reduces in low frequency (LF) region which could be used for noise cancellation, SONAR and oceanography applications. Extensive analytical modeling in conjunction with experiments were conducted involving structure-fluid-acoustic interaction to determine the operational physical behavior of TAPs. Numerical model combines all the controlling steps from power input to acoustic wave generation to the propagation in outer fluid media. Power input to the computational domain is used to determine the frequency dependent thermal diffusive length which governs the generation of TA wave. MWNT yarns/fibers/threads were also designed to harvest ocean wave energy (mechanical to electrical energy conversion). These yarn-based harvesters electrochemically convert tensile or torsional mechanical energy into electrical energy without requiring an external bias voltage. Harvesters were developed by spinning sheets of forest-drawn MWNTs into high-strength yarns. SMA wires exhibit two unique properties: thermally induced martensite to austenite phase transformation and super-elasticity (stress-induced martensitic transformation). These properties were implemented for developing the low-grade thermal energy harvesters (thermal to electrical energy conversion). More than half of the energy generated worldwide is lost as unused thermal energy because of the lack of efficient methodology for harnessing the low-grade heat. A systematic study is presented here that takes into account all the key steps in thermal to electrical conversion such as material optimization, thermal analysis and electrical conditioning to deliver the efficient harvester. Next using thin sheets of piezoelectric materials, strain energy harvesting from automobile tires is studied (strain to electrical conversion. Flexible organic piezoelectric material was utilized for transduction in the harvester for continuous power generation and simultaneous sensing of the variable strain experienced by tire under different driving conditions. Using sensors mounted on a real tire of a mobile test rig, measurements were conducted on different terrains with varying normal loads and speeds to quantify the sensitivity and self-powered sensing operation. / Doctor of Philosophy / This dissertation studies the potential of carbon nanotubes yarns and sheets, piezoelectric sheets and shape memory alloy wires for energy conversion applications. Multiwalled carbon nanotubes (MWNTs) are known for their unique electrical and thermal properties. Large surface area, solid state self-suspended carbon nanotube sheets having extremely low heat capacity per unit area were utilized for design of thermoacoustic projectors operating over a wide range of frequencies. Detailed numerical modeling and experiments were conducted for understanding the acoustics generation from MWNT sheets. Another potential application for MWNT yarns is in ocean wave energy harvesting, where these yarn based harvesters convert tensile mechanical energy into electrical energy. Harvesters were developed by spinning sheets of MWNTs into high-strength yarns. SMA exhibits unique phase change behavior on mechanical and thermal loading, which were utilized for converting low-grade thermal energy into electrical energy. At low temperature gradients, where there is lack of methodologies for converting thermal energy into electrical energy, SMA wire-based energy harvesters are shown to provide ultra-high power density. Extensive experimentation in conjunction with multi-physics modeling is conducted to provide understanding of energy losses occurring during the thermal to electrical conversion. Lastly, this dissertation investigates the mechanical to electrical conversion using organic piezoelectric materials. Self-powered strain sensing mechanism for autonomous vehicle will provide new capabilities in monitoring the dynamics and allow developing additional automated controls to assist the driver performance.