{"id":36107,"date":"1998-01-01T00:00:00","date_gmt":"1998-01-01T00:00:00","guid":{"rendered":"https:\/\/www.deberes.net\/tesis\/sin-categoria\/efecto-de-la-arquitectura-molecular-en-la-reologia-de-polietilenos-de-origen-metalocenico\/"},"modified":"1998-01-01T00:00:00","modified_gmt":"1998-01-01T00:00:00","slug":"efecto-de-la-arquitectura-molecular-en-la-reologia-de-polietilenos-de-origen-metalocenico","status":"publish","type":"post","link":"https:\/\/www.deberes.net\/tesis\/quimica\/efecto-de-la-arquitectura-molecular-en-la-reologia-de-polietilenos-de-origen-metalocenico\/","title":{"rendered":"Efecto de la arquitectura molecular en la reolog\u00eda de polietilenos de origen metalocenico."},"content":{"rendered":"<h2>Tesis doctoral de <strong>  Vega Borrego Juan  Francisco <\/strong><\/h2>\n<p>Los m\u00e9todos de polimerizaci\u00f3n mediante cat\u00e1lisis metaloc\u00e9nica han supuesto un relanzamiento de las poliolefinas, tanto desde el punto de vista cient\u00edfico como industrial. Los nuevos materiales sintetizados mediante estas t\u00e9cnicas presentan unas propiedades f\u00edsicas nunca vistas en este tipo de pol\u00edmeros, acompa\u00f1adas por unas propiedades en el procesado casi inmejorables. Esto es una consecuencia del control que los sistemas catal\u00edticos de metaloceno ejercen sobre la arquitectura molecular de los pol\u00edmeros que sintetizan.  permiten la incorporaci\u00f3n de un elevado contenido en comon\u00f3mero y de una peque\u00f1a cantidad de ramificaci\u00f3n de cadena larga manteniendo la polidispersidad en valores muy discretos: entre 2 y 3. Por otro lado existe la posibilidad de dise\u00f1ar sistemas catal\u00edticos espec\u00edficos para obtener materiales con distribuciones de pesos moleculares bimodales.  el estudio presentado pone de manifiesto que la reolog\u00eda es capaz de relacionar estas variables moleculares con el comportamiento de los materiales durante el procesado, e incluso de determinar cualitativamente la existencia de estructuras, tales como las ramificaciones de cadena larga en una extensi\u00f3n tan baja que no pueden ser determinadas mediante las t\u00e9cnicas convencionales, como la cromatrograf\u00eda de permeaci\u00f3n el gel o la resonancia magn\u00e9tica nuclear. Se ha visto que este tipo de estructuras causa un enorme efecto en el comportamiento reol\u00f3gico a bajas velocidades de deformaci\u00f3n de los materiales, con respecto a los pol\u00edmeros que no las presentan (los pol\u00edmeros lineales): aumento de la viscosidad newtoniana y del tiempo de ralajaci\u00f3n, mayor car\u00e1cter pseudopl\u00e1stico, o variaci\u00f3n de la viscosidad con la velocidad de deformaci\u00f3n, y mayor elasticidad del fundido. Sin embargo la variable que nos permite relacionar estos comportamientos con la existencia de ramificaci\u00f3n de cadena larga es la energ\u00eda de activaci\u00f3n, par\u00e1metro independient<\/p>\n<p>&nbsp;<\/p>\n<h3>Datos acad\u00e9micos de la tesis doctoral \u00ab<strong>Efecto de la arquitectura molecular en la reolog\u00eda de polietilenos de origen metalocenico.<\/strong>\u00ab<\/h3>\n<ul>\n<li><strong>T\u00edtulo de la tesis:<\/strong>\u00a0 Efecto de la arquitectura molecular en la reolog\u00eda de polietilenos de origen metalocenico. <\/li>\n<li><strong>Autor:<\/strong>\u00a0  Vega Borrego Juan  Francisco <\/li>\n<li><strong>Universidad:<\/strong>\u00a0 Pa\u00eds vasco\/euskal herriko unibertsitatea<\/li>\n<li><strong>Fecha de lectura de la tesis:<\/strong>\u00a0 01\/01\/1998<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<h3>Direcci\u00f3n y tribunal<\/h3>\n<ul>\n<li><strong>Director de la tesis<\/strong>\n<ul>\n<li>Pedro Antonio Santamar\u00eda Ibarburu<\/li>\n<\/ul>\n<\/li>\n<li><strong>Tribunal<\/strong>\n<ul>\n<li>Presidente del tribunal: Evaristo Riande Garcia <\/li>\n<li>Juan  Jos\u00e9 Iruin Sanz (vocal)<\/li>\n<li>Antonio Mu\u00f1oz-escalona Lafuente (vocal)<\/li>\n<li>Cr\u00edspulo Gallegos Montes (vocal)<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Tesis doctoral de Vega Borrego Juan Francisco Los m\u00e9todos de polimerizaci\u00f3n mediante cat\u00e1lisis metaloc\u00e9nica han supuesto un relanzamiento de las 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