Polymer nanocomposites (PNCs) have gained significant interest because they have outstanding performance that allows cost reduction, weight reduction, and product improvement. This research study focuses on the manufacture and characterization of PNCs in order to explore their potential in automotive applications. More specifically, polypropylene (PP) nanocomposites reinforced with xGnP and nanokaolin were fabricated by manufacturing methods that optimize their performances. Exfoliated graphite nanoplatelets (xGnP) are promising nanofillers that are cost effective and multifunctional with superior mechanical, thermo-mechanical and electrical properties. Nanokaolin is a newly introduced natural mineral mind in Georgia that has not been studied as of now. PNCs reinforced with these two nanofillers were characterized in terms of mechanical, thermo-mechanical, and various other properties, and then compared to talc- reinforced PP composites, which are the current state of the art for rear bumpers used by Honda Motor. Characterization results indicated that xGnP had better performance than talc and nanokaolin. Furthermore, the addition of xGnP introduces electrical conductivity in the PNCs, leading to more potential uses for PNCs in automotive applications such as the ability to be electrostatic painted. In order to fabricate PNCs with a desired conductivity value, there is need for a design tool that can predict electrical conductivity. Existing electrical conductivity models were examined in terms of model characteristics and parameters, and model predictions were compared to the experimental data. The percolation threshold is the most important parameter in these models, but it is difficult to determine experimentally, that is why a correlation between thermo-mechanical properties and electrical conductivity is also investigated in this study.

Reproduction de : Thèse de doctorat : Chimie et physico-chimie des polymères : Le Mans : 2008. / Titre provenant de l'écran-titre. Bibliogr. p. 157-173.

Thèse de doctorat : Physique : Nancy 1 : 2009. / Titre provenant de l'écran-titre.

Thesis (M.S.)--University of Central Florida, 2009. / Adviser: Kuo-Chi Lin. Includes bibliographical references (p. 84-92).

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Glass matrix composites containing a conducting filler such as antimony tin oxide (ATO) or silicon carbide whiskers (SiCw) have the potential for applications such as transparent electrodes, heating elements, and electromagnetic shielding. For these applications, the composite performance is highly dependent on the microstructure of the composite and the interactions the added filler has with one another. In this research, borosilicate glass-matrix composites were fabricated using a processing method that creates segregated percolated networks at low concentrations of conducting fillers. The conducting fillers were hot pressed with the glass microspheres at temperatures near the glass transition temperature (550°C) using various pressures. Upon hot-pressing at these low temperatures, the glass microspheres deformed into faceted polyhedra and the fillers were displaced to the edges of the glass particles, resulting in percolation. The processing method used in this study was able to bypass many of the current composition and densification issues associated with the creation of percolated networks in glass composites. In some cases, the formation of these percolated networks resulted in a 12-13 orders of magnitude decrease in the resistivity. Using a non-destructive electrical measurement technique, ac impedance spectroscopy (IS), the changes in the electrical properties were tracked as the conducting networks developed. Using IS in conjunction with other techniques, correlations were made between the electrical properties, the filler interfaces, and the influence the processing parameters had on the development of the percolation networks within these composites.

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Unconventional natural gas resources, particularly tight gas sands, constitute a significant percentage of the natural gas resource base and offer abundant potential for future reserves and production. The premise of this research is that several unique characteristics of these rocks are the consequence of post depositional diagenetic processes including mechanical compaction, quartz and other mineral cementation, and mineral dissolution. These processes lead to permanent alteration of the initial pore structure causing an increase in the number of isolated and disconnected pores and thus in the tortuosity. The objective of this research is to develop a pore scale model of the geological processes that create tight gas sandstones and to carry out drainage simulations in these models. These models can be used to understand the flow connections between tight gas sandstone matrix and the hydraulic fractures needed for commercial production rates. We model depositional and diagenetic controls on tight gas sandstones pore geometry such as compaction and cementation processes. The model is purely geometric and begins by applying a cooperative rearrangement algorithm to produce dense, random packings of spheres of different sizes. The spheres are idealized sand grains. We simulate the evolution of these model sediments into low-porosity (3% to 10%) sandstone by applying different amount of ductile grains and quartz precipitation. A substantial fraction of the original pore throats in the sediment are closed by the simulated diagenetic alteration. Thus, the pore space in typical tight gas sandstones is poorly connected, and is often close to being completely disconnected, with significant effect on flow properties. The drainage curves for model rocks were computed using invasion percolation in a network taken directly from the grain-scale geometry and topology of the model. The drainage simulations show clear percolation behavior, but experimental data frequently do not. This implies that either network models based on intergranular void space are not a good tool for modeling of tight gas sandstone or the experiments are not correctly done on tight gas samples. In addition to reducing connectivity, the porosity-reducing mechanisms change pore throat size distributions. These combined effects shift the drainage water relative permeability curve toward higher values of water saturation, and gas relative permeability shifts toward smaller values of gas. Comparison of simulations with measured relative permeabilities shows a good match although same network fail to match drainage curves. This could happens because the model gives the right fluid configuration but at the wrong values of curvature and saturation. The significance of this work is that the model correctly predicts the relative permeabilities of tight gas sandstones by considering the microscale heterogeneity. The porosity reduction due to ductile grain deformation is a new contribution and correctly matches with experimental data from literature. The drainage modeling of two-phase flow relative permeabilities shows that the notion of permeability jail, a range of saturations over which both gas and water relative permeabilities are very small, does not occur during drainage. / text

The main aim of this work is to study percolation theory on regular two dimensional / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2002.