PHYSICCS IN POLYMER

Author: GARCIA MORALES VLADIMIR.
Year: 2005.
University: VALENCIA [www.uv.es].
Place of defense: FACULTAD DE FISICA.
Place of preparation: Facultad de Física.

Summary: This thesis is developed formalism of the termoestadística valid for systems at the nanoscale and some applications to nanostructures interfaciales. After a brief introduction, Chapter 2 presents two formalism equilibrium holds for the nanometer scale: nanotermodinámica (NT) and non-extensive statistical mechanics (NSM), establishing the correct thermodynamic forces of the NSM and the physical meaning of the parameter q entrópico on which it depends. Here are four applications to develop these formalities: liquid clusters near the critical stage of transition from wet; shifting of pKa of weak acids in the presence of strong bases, links and bridge hydrogen adsorption of divalent cations; capacitance nanostructures interfaciales and a theory for the distribution profiles of contraiones valid for arbitrary coupling. Chapter 3 contains four studies on ion transport through multi-polielectrólitos and polielectrólitos and gold nanoparticles. It develops first model electrodifusión which takes into account the effects of electrostatic partitioning and accurately describe the curves current / voltage steady state observed in multilayers of polielectrólitos with different ions. The following provides a model of capillary membrane applied to experiments electrochemical impedance observed in multilayers of polielectrólitos and policationes and gold nanoparticles. The model allows to quantify the changes observed in the impedance depending on the state of growth in the multi-species electroactivas and electrolyte medium used and the temperature. In Chapter 4 presents the findings of work.

Author: GONZÁLEZ PEÑA JORGE IGNACIO.
Year: 2006.
University: VALLADOLID [www.uva.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: The closed cell foam polymer, materials are two phases in which a number of gas bubbles are dispersed in a polymer matrix. These materials have a wide range of applications in various sectors such as construction, automotive, packaging, sports and so on. It is widely accepted that the physical properties of these materials depend on factors such as density, chemical composition, cell structure and morphology of polymer base. In this investigation have been studied foam blocks, dimensions 2x1x.0.9m3, produced by compression molding. This manufacturing process is characterized by foam lead to a heterogeneous structure in terms of density, cell size and orientation of the crystalline phase, all these features vary considerably over the thickness of the block. That diversity is a source of problems in the transformed foam (sliced and thermoforming) and its subsequent implementation. Through a series of thermal treatments, applied on a block of foam low density polyethylene, can reduce internal tensions and the heterogeneity of the properties of the material. This research has attempted to reveal and to model the mechanisms controlling the anomalous behavior of these materials are conducting a systematic study with techniques such as SEM, DSC, TMA. During the research work has reached the following conclusions: It has perfected a method of work that has characterized the behavior of heterogeneous blocks polyethylene foam produced by compression molding. It highlights the analysis termomecánico as a particularly sensitive technique for measuring the anisotropy of the cell structure. Among this series of heterogeneities has proven how targeting cell plays a decisive role in the mechanical and thermal response of the blocks of foam. Thermal treatments not homogeneous with a slow cooling rate (the temperature reached on the surface of the block was higher than that achieved in the middle of it), they are able to homogenize the thermal expansion of the block of foam in front of the temperature increase. From the point of view of the microscopic structure treatments have reduced the molecular orientation presented by the polymer matrix and its distribution thicknesses lamelares. The cellular structure of the original cell has a different orientation, depending on the area of the block. These differences can be reduced by heat treatment, these being the most effective, as is the slower cooling rate from temperature treatment. The treatments tend to make isotropic whole cell. From the viewpoint of the thermal properties of foams, cell geometry substantially affects the response of the foam off the temperature. This heterogeneous behavior can be reduced through a series of heat treatments. The thermal conductivity has shown no significant trend with heat treatments. The study of the mechanical response of the foam in compression deformation at low speeds, heat treatments made it possible to conclude that the geometry cell plays an important role in the response to compression at low speeds of deformation of the foam. Thermal treatments modify both the effort to collapse as the module Young. It has analyzed a theoretical model for calculating the volume thermal expansion coefficient. He predicts in a reasonable behavior versus temperature. The deviations from the values given 8 s by the 3e8 model respect to the experimental values are mainly due to the properties of the polymer matrix and the existence of folds in the cell walls. It has made the study of thermoforming, "thermoforming within a mold" characterized by its simplicity and technological industry requires.