Publication: Relajación estructural en nanocompuestos basados en resina epoxi monitorizado por fluorescencia
Loading...
Identifiers
Publication date
2013-05
Defense date
2013-05-14
Authors
Tutors
Journal Title
Journal ISSN
Volume Title
Publisher
Impact
Export
Abstract
Las propiedades mecánicas de los materiales compuestos de matriz termoestable dependen, entre otras, de la capacidad de la interfase para transmitir los esfuerzos desde la matriz al refuerzo. Probablemente, los agentes de acoplamiento son los más usados para generar estructuras y propiedades en la interfase adecuadas. Existen muchas teorías intentando explicar cuál es exactamente el origen de la mejora en el comportamiento del material compuesto cuando se realizan modificaciones en la superficie del refuerzo. Sin embargo, no se ha prestado mucha atención a la relación de la interfase y las relajaciones de la matriz polimérica con las propiedades del material compuesto. Normalmente, se acepta que la región de acoplamiento tiene un espesor de 100 a 500 nm. Por lo tanto, incluso la microcalorimetría tendría dificultades para determinar relajaciones térmicas en aquellos lugares específicos. Sin embargo, el uso de la respuesta fluorescente procedente de marcadores y sondas fluorescentes ha llegado a ser una poderosa herramienta para realizar el seguimiento de los cambios en sus entornos tales como la polaridad y/o la rigidez. Por este motivo se propone su empleo como sensores locales de transiciones térmicas en la región de acoplamiento de los materiales compuestos. En este trabajo se ha utilizado la respuesta fluorescente del dansilo para estudiar las relajaciones térmicas en un material compuesto. En este trabajo se utilizará la técnica de fluorescencia, además de una técnica convencional como es la calorimetría diferencial de barrido, para el estudio de la relajación estructural de las cadenas polímericas en una resina epoxi con nanopartículas de sílice a nivel molecular, localizando la sonda fluorescente en la matriz o en la interfase. En la parte correspondiente a la fluorescencia se medirá la variación de la emisión fluorescente del fluoróforo anclado en la interfase o en la matriz, analizando dos parámetros fotofísicos (la intensidad integrada de fluorescencia y el primer momento asociado a la banda de emisión fluorescente en número de ondas) en función de la temperatura. Con ello, podremos saber aproximadamente la temperatura a la cual tiene lugar la transición vítrea del material compuesto. En lo que respecta a la segunda técnica, la utilizaremos para estudiar los procesos de relajación que tienen lugar durante el enfriamiento de las muestras, analizando distintos parámetros como la temperatura vítrea, la temperatura ficticia, la capacidad calorífica o la energía aparente de activación. Finalmente, compararemos los resultados obtenidos por las dos técnicas en cuanto a los valores de las temperaturas de transición vítreas se refiere y analizaremos si la tendencia seguida por esta temperatura en todas las muestras es similar en las dos técnicas. _______________________________________________________________________________________________________________________________
The mechanical properties of composites depend, among others, on the ability of the interface to transfer stress from the matrix to the reinforcement. Probably, the silane coupling agents are the most used to generate adequate interfaces structures and properties. There are many theories trying to explain what is exactly the origin of the improvement in the composite performance when surface modifications on the reinforcement are done. However, not much attention has been paid relating the interfacial and bulk polymer relaxations with the properties of the composite. Usually, it is accepted the coupling region has a thickness of 100 to 500 nm. Therefore, even microcalorimetry would have many difficulties to determinate thermal relaxations at those specifics sites. However, The use of fluorescent response from labels and probes has become a very powerful tool to follow changes in its surrounding such as polarity and/or rigidity. Due to this, they are proposed to be use for sensing local thermal transitions at the coupling region of a composite as a function of its structure. In the present essay dansyl fluorescence response has been used to study thermal relaxations in a composite material. In this essay will be used the fluorescence technique, in addition to the conventional technique as is the differential scanning calorimetry, for the study of the structural relaxation of the polymeric chains in an epoxy resin with silica nanoparticles at the molecular level, locating the fluorescent probe in the bulk or the interface. In the part corresponding to the fluorescence was measured the variation of the fluorescent emission of fluoroforo anchored in the interface or in the matrix, analyzing two parameters fotofisics (the integrated intensity of fluorescence and the first time associated with the fluorescent emission band in number of waves) as a function of temperature. With this, we can know about the temperature at which takes place the glass transition of the composite material. With regard to the second technique, we will use it to study the relaxation processes that take place during the cooling of the samples, analyzing several parameters such as glass temperature, fictitious temperature, the heat capacity or the apparent activation energy. Finally, we will compare the results obtained by the two techniques in regard to the values of the glass transition temperatures refers and analyze if the trend followed by this temperature in all the samples are similar in the two techniques.
The mechanical properties of composites depend, among others, on the ability of the interface to transfer stress from the matrix to the reinforcement. Probably, the silane coupling agents are the most used to generate adequate interfaces structures and properties. There are many theories trying to explain what is exactly the origin of the improvement in the composite performance when surface modifications on the reinforcement are done. However, not much attention has been paid relating the interfacial and bulk polymer relaxations with the properties of the composite. Usually, it is accepted the coupling region has a thickness of 100 to 500 nm. Therefore, even microcalorimetry would have many difficulties to determinate thermal relaxations at those specifics sites. However, The use of fluorescent response from labels and probes has become a very powerful tool to follow changes in its surrounding such as polarity and/or rigidity. Due to this, they are proposed to be use for sensing local thermal transitions at the coupling region of a composite as a function of its structure. In the present essay dansyl fluorescence response has been used to study thermal relaxations in a composite material. In this essay will be used the fluorescence technique, in addition to the conventional technique as is the differential scanning calorimetry, for the study of the structural relaxation of the polymeric chains in an epoxy resin with silica nanoparticles at the molecular level, locating the fluorescent probe in the bulk or the interface. In the part corresponding to the fluorescence was measured the variation of the fluorescent emission of fluoroforo anchored in the interface or in the matrix, analyzing two parameters fotofisics (the integrated intensity of fluorescence and the first time associated with the fluorescent emission band in number of waves) as a function of temperature. With this, we can know about the temperature at which takes place the glass transition of the composite material. With regard to the second technique, we will use it to study the relaxation processes that take place during the cooling of the samples, analyzing several parameters such as glass temperature, fictitious temperature, the heat capacity or the apparent activation energy. Finally, we will compare the results obtained by the two techniques in regard to the values of the glass transition temperatures refers and analyze if the trend followed by this temperature in all the samples are similar in the two techniques.
Description
Keywords
Nanotecnología, Materiales compuestos, Materiales nanocompuestos, Nanocompuestos epoxy, Propiedades mecánicas, Fluorescencia