A co-polymer made from Polyvinyl Alcohol and Polyacrylic Acid (PVA-PAA) has been synthesized to form new robotic actuation systems which use the contractile and variable compliance properties of this material. The stimulation of these fibres is studied (particularly chemical activation using acetone and water), as are the factors which influence the response, especially those relating to its performance as an artificial muscle. Mathematical models and simulations of the dynamics of the polymeric strips have been developed, permitting a thorough analysis of the performance determining parameters. Using these models a control strategy has been designed and implemented, with experimental results being obtained for a gripper powered by a flexor/extensor pair formed using these polymeric actuators. An investigation of a second property of the polymer, its variable compliance is alsoincluded. Use of this feature has lead to the design, construction and testing of a multi degree-of-freedom dextrous hand, which despite having only a single actuator, can exercise independent control over each joint.

No description available.

Thesis (M.Eng.). / Written for the Dept. of Biomedical Engineering. Title from title page of PDF (viewed 2008/07/29). Includes bibliographical references.

Thesis (Ph.D.) -- University of Western Sydney, 2004. / A thesis presented to the University of Western Sydney, Centre for Advanced Food Research, in fulfilment of the requirements for the degree of Doctor of Philosophy in Advanced Food Science (& Food Packaging Science). Includes bibliography.

Zugl.: Köln, Universiẗat, Diss., 2008.

Thesis (Ph.D.)--Technical University of Denmark, 2001. / Title from PDF title page (viewed on Feb. 20, 2009). "September 2001". Includes bibliographical references (p. 99-104).

Orientador: Alcides Lopes Leão / Banca: Elisabete Frollini / Banca: Pedro de Magalhães Padilha / Resumo: O momento atual de maior preocupação ambiental global, a crescente escassez dos recursos fósseis, bem como as novas regulagens ambientais força a busca por materiais que sejam renováveis e compatíveis com o ambiente. Novos materiais estão sendo desenvolvidos a partir de várias fontes naturais e, entre eles a celulose é o mais abundante dos polímeros naturais e um dos mais utilizados. Logo, o objetivo desta dissertação de mestrado foi obter nanofibras de celulose tendo como fonte a fibra vegetal de curauá. Os processos utilizados foram químicos e mecânicos, baseados nos processos de polpação e branqueamento, a fim de isolar a celulose, seguido de processos mecânicos para atingir a escala nanométrica. As nanofibras de celulose propiciam vantagens como melhoria nas propriedades mecânicas e de barreira, além de manter a transparência de polímeros em geral. A fim de comprovar a capacidade de reforço em matrizes poliméricas, as nanofibras de celulose obtidas foram incorporadas nas mesmas. No entanto, para evitar a tendência de aglomeração das nanofibras, principalmente quando retiradas do meio aquoso, o álcool polivinílico (pva) foi escolhido como a matriz polimérica a ser testada, devido à sua compatibilidade com nanofibras de celulose, por ambos serem de natureza hidrofílica, o que aumenta a compatibilidade interfacial de fases entre a nanocelulose e a matriz escolhida. Após a incorporação das nanofibras na matriz polimérica ocorreram significativas melhoras nas propriedades mecânicas da matriz. Ao incorporar 4% de nanofibras da celulose de curauá obteve-se um ganho de 36% e 67% para a tração e para o módulo de young, respectivamente. Com 5% de nanofibras, o aumento nas propriedades foram ainda mais significativos em torno de 44% para a tração máxima e 448% para o módulo de young / Abstract: Nowadays is a era of greatest environmental concern, with growing scarcity of fossil resources, as well as new environmental regulations obligating the search for materials that are renewable and environmentally friendly. New materials are being developed from various natural sources, and among them, cellulose is the most abundant natural polymers and the one most used. Therefore, the purpose of this thesis was to obtain cellulose nanofibers fibers from curaua plant. The procedures used were based on chemical and mechanical treatment. Pulping and bleaching, in this sequence were done in order to isolate the cellulose, followed by mechanical processes to achieve the nanometer scale. The cellulose nanofibers provide advantages such as improvement of mechanical properties and barrier, besides maintaining transparency of polymers in general. To prove the capacity of reinforcement in polymer matrices, the cellulose nanofibers obtained were incorporated into them. However, to avoid the tendency of nanofibers agglomeration when removed from water, the polyvinyl alcohol (PVA) was chosen as the polymer matrix to be tested, for the reasons that both are hydrophilic in nature and compatible to cellulose nanofibers, which increases the interface between the matrix and the nanocelulose chosen. After the incorporation of nanofibers in the polymer matrix, a significant improvement were observed in its mechanical properties by incorporating 4% of cellulose nanofiber curauá which provided a gain of 36% and 67% for tension and Young's modulus, respectively. With 5% of nanofibers, the increase in properties was even more significant at around 44% for maximum tension and 448% for Young's modulus / Mestre

Made available in DSpace on 2014-06-11T19:24:41Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-09-03Bitstream added on 2014-06-13T18:52:26Z : No. of bitstreams: 1 souza_sf_me_botfca.pdf: 1653750 bytes, checksum: 3aa87de3ba9ede42d6a64a6e7aef2e61 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O momento atual de maior preocupação ambiental global, a crescente escassez dos recursos fósseis, bem como as novas regulagens ambientais força a busca por materiais que sejam renováveis e compatíveis com o ambiente. Novos materiais estão sendo desenvolvidos a partir de várias fontes naturais e, entre eles a celulose é o mais abundante dos polímeros naturais e um dos mais utilizados. Logo, o objetivo desta dissertação de mestrado foi obter nanofibras de celulose tendo como fonte a fibra vegetal de curauá. Os processos utilizados foram químicos e mecânicos, baseados nos processos de polpação e branqueamento, a fim de isolar a celulose, seguido de processos mecânicos para atingir a escala nanométrica. As nanofibras de celulose propiciam vantagens como melhoria nas propriedades mecânicas e de barreira, além de manter a transparência de polímeros em geral. A fim de comprovar a capacidade de reforço em matrizes poliméricas, as nanofibras de celulose obtidas foram incorporadas nas mesmas. No entanto, para evitar a tendência de aglomeração das nanofibras, principalmente quando retiradas do meio aquoso, o álcool polivinílico (pva) foi escolhido como a matriz polimérica a ser testada, devido à sua compatibilidade com nanofibras de celulose, por ambos serem de natureza hidrofílica, o que aumenta a compatibilidade interfacial de fases entre a nanocelulose e a matriz escolhida. Após a incorporação das nanofibras na matriz polimérica ocorreram significativas melhoras nas propriedades mecânicas da matriz. Ao incorporar 4% de nanofibras da celulose de curauá obteve-se um ganho de 36% e 67% para a tração e para o módulo de young, respectivamente. Com 5% de nanofibras, o aumento nas propriedades foram ainda mais significativos em torno de 44% para a tração máxima e 448% para o módulo de young / Nowadays is a era of greatest environmental concern, with growing scarcity of fossil resources, as well as new environmental regulations obligating the search for materials that are renewable and environmentally friendly. New materials are being developed from various natural sources, and among them, cellulose is the most abundant natural polymers and the one most used. Therefore, the purpose of this thesis was to obtain cellulose nanofibers fibers from curaua plant. The procedures used were based on chemical and mechanical treatment. Pulping and bleaching, in this sequence were done in order to isolate the cellulose, followed by mechanical processes to achieve the nanometer scale. The cellulose nanofibers provide advantages such as improvement of mechanical properties and barrier, besides maintaining transparency of polymers in general. To prove the capacity of reinforcement in polymer matrices, the cellulose nanofibers obtained were incorporated into them. However, to avoid the tendency of nanofibers agglomeration when removed from water, the polyvinyl alcohol (PVA) was chosen as the polymer matrix to be tested, for the reasons that both are hydrophilic in nature and compatible to cellulose nanofibers, which increases the interface between the matrix and the nanocelulose chosen. After the incorporation of nanofibers in the polymer matrix, a significant improvement were observed in its mechanical properties by incorporating 4% of cellulose nanofiber curauá which provided a gain of 36% and 67% for tension and Young's modulus, respectively. With 5% of nanofibers, the increase in properties was even more significant at around 44% for maximum tension and 448% for Young's modulus

M.Sc. (Chemistry) / The fabrication of multiwalled carbon nanotube/polyvinyl chloride (PVC) composites and a study of their thermal, fire retardancy and mechanical properties are reported. Triphenylphosphine linked - multiwalled carbon nanotube (TPP-MWCNT) and pristine MWCNT were used. The MWCNT were embedded in the polymer matrix through melt blending and solvent casting. The phosphorylation of the MWCNT and their dispersion in the PVC matrix was characterized by scanning electron microscopy and Raman spectroscopy. Thermal analysis of the nanocomposites by thermal gravimetric analysis (TGA) in both solvent casting and melt bending processes, showed different results when compared with the neat PVC. The modulus of the MWCNTs / PVC nanocomposites synthesized via melt blending increased, whilst there was a reduction in their tensile strength, indicating a decrease in polymer toughness. The tensile modulus and strength of MWCNTs / PVC nanocomposite synthesized via Solvent casting decreased whilst there was an increase in Tpp-MWCNT/PVC nanocomposite when compared with its counterpart MWCNTs / PVC nanocomposite, indicating an increase in stiffness and strength. The limited oxygen index (LOI) fire retardant tests of all the neat PVC and its nanocomposites showed no value difference.

Starch is a natural polymer occurring in the seeds, tubers and stems of many plants, including maize. It is a mixture of two polymers: linear amylose and highly branched amylopectin. The ratio and the molar masses of the two polymers depend on the starch source, giving rise to different starch properties. Thermoplastic starch (TPS) was obtained by gelatinising a dry-blend mixture of maize starch, water, plasticisers and additives in a single-screw laboratory extruder. The TPS formed is a translucent amorphous material that could be shaped into pellets and injection-moulded into a variety of articles, just like conventional plastics [Shogren et al., 1994]. The advantages of TPS are that it is cheap and fully biodegradable. However, because of its hydrophilic nature, its properties and dimensional stability are influenced by moisture (humidity). It is also not easily processed like conventional plastics and the freshly moulded material ages, i.e. its properties change over time. The latter is caused by retrogradational structural changes which include helix formation and the crystallisation that occurs above the glass transition temperature [Myllärinen et al., 2002]. The unacceptable physical and processing properties of TPS were improved by blending with other polymers. The objective of this work was to determine the effects of water and glycerol content and the starch source or type on the mechanical properties of maize-based TPS. In addition, the effect of gypsum filler and polyamides or polyvinyl butyral (PVB) as modifying agent was also investigated. The PVB was based on material recycled from automotive windscreens. As with the thermoplastic starch, the thermoplastic/polymer blends, e.g. polyvinyl butyral, were also prepared using a single-screw extruder. After pelletisation, the materials were conditioned at 30 °C and a relative humidity of 60%. Tensile test specimens were prepared by injection moulding. Samples were characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM), dynamic mechanical analysis (DMA) and tensile testing. The effect of environmental conditions (temperature and humidity or water submersion) on the ageing of the samples was investigated using tensile properties as a measure. Initial extrusion and moulding trials revealed that the TPS compounds were very difficult to process. Difficulties were encountered with feeding the dry blends into the compounding extruder. The moulded samples adhered strongly to the mould walls, especially the sprue part. These problems were overcome by adding 2,5% precipitated silica to improve the flowability of the dry blends and stearyl alcohol at ca. 1,5% as a processing aid. The latter performed as an external lubricant and mould-release agent. Nevertheless, for some compositions it was also necessary to use ‘Spray-and-Cook’ as mould-release agent during injection moulding. The results show that HiMaizeTM, a high-amylose maize starch, provided the best properties in TPS and its blends. Further improvements in properties were obtained by blending with low-molecular-weight hot-melt adhesive-grade polyamides (Euremelt 2138 and 2140), engineering polyamide (EMS Grilon CF 62 BSE) or low amounts of PVB. The properties of all the compounds investigated were affected by moisture content and also by ageing. The TPS-PVB blends showed highly non-linear composition-dependence. SEM and DMA revealed a phase separation for all the TPS-PVB blend compositions investigated. The tensile properties were negatively affected by ageing in a high-humidity environment and they deteriorated rapidly when the samples were soaked in water. Synergistic property enhancement was observed for a compound containing 22% thermoplastic starch. It featured a higher tensile strength, showed better water resistance and was significantly less affected by ageing. At higher PVB levels, the property dropped to values that were lower than expected from the linear blending rule. / Thesis (PhD)--University of Pretoria, 2008. / Chemical Engineering / unrestricted