Zugl.: Hannover, Universiẗat, Diss., 2006.

Universiẗat, Diss., 2004--Freiburg (Breisgau).

No description available.

Multifunctional Dielectric Elastomer (DE) devices are well established as actuators, sensors and energy harvesters. Since the invention of the Dielectric Elastomer Switch (DES), a piezoresistive electrode that can directly switch charge on and off, it has become possible to expand the wide functionality of DE structures even more. We show the application of fully soft DE subcomponents in biomimetic robotic structures. It is now possible to couple arrays of actuator/switch units together so that they switch charge between themselves on and off. One can then build DE devices that operate as self-controlled oscillators. With an oscillator one can produce a periodic signal that controls a soft DE robot { a DE device with its own DE nervous system. DESs were fabricated using a special electrode mixture, and imprinting technology at an exact pre-strain. We have demonstrated six orders of magnitude change in conductivity within the DES over 50% strain. The control signal can either be a mechanical deformation from another DE or an electrical input to a connected dielectric elastomer actuator (DEA). We have demonstrated a variety of fully soft multifunctional subcomponents that enable the design of autonomous soft robots without conventional electronics. The combination of digital logic structures for basic signal processing, data storage in dielectric elastomer ip-ops and digital and analogue clocks with adjustable frequencies, made of dielectric elastomer oscillators (DEOs), enables fully soft, self-controlled and electronics-free robotic structures. DE robotic structures to date include stiff frames to maintain necessary pre-strains enabling sufficient actuation of DEAs. Here we present a design and production technology for a first robotic structure consisting only of soft silicones and carbon black.

Ionomers are valued for their exceptional physical properties, antimicrobial activity and superior adhesion to high surface energy solids and polymer blend components. Carboxylate, or sulfonate derivatives, of ethylene-rich thermoplastics are the most commercially available ionomers. Elastomeric ionomers bearing quaternary ammonium and phosphonium halide functionality have a literary standing in both scientific and patent-based publications. Currently cationic ionomers have shown great prominence in their inactivity to a wide range of bacteria and fungi. The specific focus of this research is in the derivatives of isobutylene-rich elastomers due to their exceptional impermeability, oxidative stability and vibration dampening characteristics. Imidazole-derived ionomers support a wider range of ionomer chemistry compared to ammonium and phosphonium analogues. N alkylation of nucleophiles including butyl imidazole, vinyl imidazole and 1,1’(1,4-butanediyl)bis(imidazole) by brominated poly(isobutylene-co-isoprene) yield thermally stable imidazolium bromide salts capable of supporting free radical cures and/or siliceous filler dispersions through further chemical modifications. The versatility of imidazole chemistry extends to the synthesis of isobutylene rich thermoset ionomers. This derives material properties from both a network of covalent crosslinks and a network of ion pair aggregates. Un-crosslinked elastomers are prone to creep and stress relaxation, hence a need for thermoset ionomer chemistry. Ion pairs are poorly solvated by the low dielectric constant of the polymer backbone and favoured thermodynamically by way of self assembly of the ionic functionality. The aggregation of ion pairs establishes a non covalent network of polymer chains whose dynamic mechanical properties approach those of conventional covalent thermosets comprised of carbon-carbon and/or sulfide crosslinks. However, the lability of this ionic network leads to a poor response to static loads leaving the thermoformable ionomers unqualified for engineering applications. A direct route is a more desirable method in preparing thermoset ionomers comprised of covalent crosslink networks and ionic functionality. In all, these reactive imidazolium ionomers look promising in supporting new value added applications for isobutylene rich derivatives, which include yet are not limited to elastomer thermosets, emulsions, filler composites and clay nanocomposites. / Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2013-12-11 15:34:32.691

Compósitos são materiais híbridos que resultam de associações de, pelo menos, dois tipos deferentes de materiais. O desenvolvimento da sociedade humana somente atingiu o estágio atual utilizando-se de compósitos de todo o tipo de misturas de materiais. Além disso, o desenvolvimento de compósitos com partículas cada vez menores de fase reforçante com o passar das décadas, ou precisamente, dos séculos foram as principais razões do alcance do \"estado da arte\" da ciência dos compósitos. Com relação à ciência dos compósitos, os nanocompósitos são a grande descoberta do último meio século. Seguindo tendências dos estudos na área dos compósitos, este trabalho foca obter nanocompósitos de elastômero SBR (matriz elastomérica) com argilas tratadas e não tratadas. Além disso, a avaliação de propriedades mecânicas, térmicas, reológicas, de cura, em solução e propriedades de difração de raios-X são outro alvo deste trabalho. Os compósitos foram preparados com equipamentos tradicionais de processamento de elastômeros e, depois disso, suas propriedades foram avaliadas. Considerando propriedades em difração de raios-X, somente o compósito com Cloisite 20A mostrou estrutura intercalada. Os compósitos com argilas tratadas mostraram um melhor perfil geral de propriedades, com destaque novamente para o compósito com Cloisite 20A. Todos os compósitos com argilas tratadas mostraram um menor tempo de cura. Esse comportamento se deve à presença dos sais de tratamento orgânicos dos argilominerais que modificam a densidade de ligações cruzadas e a velocidade de cura. As melhores propriedades do compósito contendo Cloisite 20A, considerando que este foi o único a demonstrar estrutura intercalada, nos permitem concluir que um nanocompósito foi obtido nesta situação. / Composites are hybrid materials which result from associations of, at least, two different kind of materials. The human society development only achieved the current stage using composites of all type of materials mixing. Besides this, the achievement of composites with smaller particles of reinforcing phases along the decades or, precisely, along centuries were the main reasons to reach the current \"state of art\" of composites science. Regarded to composites science, the nanocomposites are the major breakthrough of the last half century. Following the trends of composites science study, this work is focused on obtain nanocomposites of SBR elastomer (rubber matrix) with treated and untreated clays. In addition to this, the evaluation of mechanical, thermal, reological, rubber cure, solution stability and X-Ray diffraction properties are other main target of this work. The composites were prepared with traditional equipments of rubber processing an after the properties were measured. Considering the X-Ray diffraction properties of obtained composites, only the composite with the organoclay Cloisite 20A showed an intercalated structure. The composites containing treated clays demonstrated the better mechanical, thermal and solution stability properties, with a special highlight to the composite containing Cloisite 20A. All composites obtained with organoclays showed lower cure time. This behavior is a result of organic treatment salts of organoclays presence that is able to modify crosslink density and the cure velocity. The better properties of composite containing Cloisite 20A, considering that this composite was the only one that showed intercalated structure, enable us to conclude that a nanocomposite was obtained in this situation.

Zugl.: Hannover, Universiẗat, Diss., 2007.

Zugl.: Berlin, Techn. Universiẗat, Diss.

Techn. Universiẗat, Diss., 2002--Darmstadt.

Techn. University, Diss., 2005--Darmstadt.