{"id":99449,"date":"2018-03-11T10:20:34","date_gmt":"2018-03-11T10:20:34","guid":{"rendered":"https:\/\/www.deberes.net\/tesis\/sin-categoria\/study-of-thermal-transitions-in-polymers-by-a-multifrequency-modulated-dsc-technique\/"},"modified":"2018-03-11T10:20:34","modified_gmt":"2018-03-11T10:20:34","slug":"study-of-thermal-transitions-in-polymers-by-a-multifrequency-modulated-dsc-technique","status":"publish","type":"post","link":"https:\/\/www.deberes.net\/tesis\/termodinamica\/study-of-thermal-transitions-in-polymers-by-a-multifrequency-modulated-dsc-technique\/","title":{"rendered":"Study of thermal transitions in polymers by a multifrequency modulated dsc technique"},"content":{"rendered":"<h2>Tesis doctoral de <strong> Iria Fraga Rivas <\/strong><\/h2>\n<p>Differential scanning calorimetry (dsc) is one of the most widely used thermal analysis techniques for the study of transitions and  relaxation processes in polymers and also in other materials. It measures the heat flow as a function of time and\/or temperature, and  determines the energy released or absorbed by a sample  when it is heated (cooled) or maintained at a constant temperature. Its advantages  are that it is fast and sensitive, the amount of sample needed is small (~mg), it could be in the liquid or solid state and the sample  preparation is easier than for some other techniques.  Nevertheless, it present some drawbacks, such as not being able to separate different  overlapping transitions that happen in the same temperature range, the difficulty of detecting very weak transitions, or the requirement for  multiple experiments to determine heat capacities that increases the experimental time needed.     temperature modulated dsc techniques (tmdsc) were introduced in the market more than 16 years ago.  In these techniques a periodic  temperature modulation of small amplitude is superimposed on the underlying rate of conventional dsc.  This superposition gives two  different heating rates: the underlying and the instantaneous due to the sinusoidal signal, thus permitting a better resolution and sensitivity  (in dsc a better  resolution gives a worse sensitivity and vice versa) and the evaluation of the heat capacity in real time. Tmdsc is able to  determine not only the total heat flow but also  its two individual components usually referred to as reversing and non-reversing, thus it  is possible to separate overlapped transitions. Although tmdsc offers more information than that available by dsc it also shows some  drawbacks as  the use of lower underlying heating rates than in conventional dsc which leads to longer experiments, or the requirement of  making a separate scan for each frequency if one wishes to study, for example, the frequency dependence of a certain phenomenon.    more recently, in 2005, topem, a new technique of tmdsc from mettler -toledo, was commercialised. Instead of being based upon a periodic  modulation of the heating rate, as is the situation with other tmdsc techniques, topem uses a stochastic modulation of the heating or  cooling rate by means of random pulses of temperature. This stochastic perturbation introduces a broad frequency spectrum in the  response, which implies that topem is apparently able to determine the complex heat capacity over a range of frequencies in a single scan.    in the present thesis , a detailed description of the bases and operation of topem is presented, showing the differences between the other  calorimetric techniques, dsc and tmdsc. All the parameters which define an experiment and the parameters needed to make an evaluation  of the experimental response are explained.    the glass transition of polycarbonate is selected to make an initial study of the influence of all the different parameters (experimental and  calculation) on the results of an experiment.  Different samples are employed and different experiments by topem and adsc (tmdsc  technique specific of mettler -toledo) are performed and compared.  The limits and advantages offered by topem are observed and  presented here, and with a  more profound understanding of the technique as a result, additional materials and transitions are studied.     in the next part, an epoxy resin with a diamine is selected to be studied. The vitrification during the isothermal cure is  studied by topem.  the results are again compared with those obtained by tmdsc and the additional information obtained is analyzed and compared with  additional results obtained from the literature. With the aim to confirm some experimental data observed, a simulation is made with matlab  to confirm the experimental results. It is found that the theoretical results  not only predict the calorimetric data, but also those obtained from  dielectric analysis at higher frequencies which were extracted from the literature.     in the next part, the same  epoxy resin with a diamine is selected. The vitrification and devitrification during the non-isothermal cure  is  analyzed by topem. The results obtained permit to construct a cht diagram (conversion-time-temperature) which characterized the system.  as in the previous case a simulation is made with matlab and the theoretical results obtained compare well with the  experimental  data.     finally, some preliminary experiments related to other transitions  are presented and are planned to be studied in the future.<\/p>\n<p>&nbsp;<\/p>\n<h3>Datos acad\u00e9micos de la tesis doctoral \u00ab<strong>Study of thermal transitions in polymers by a multifrequency modulated dsc technique<\/strong>\u00ab<\/h3>\n<ul>\n<li><strong>T\u00edtulo de la tesis:<\/strong>\u00a0 Study of thermal transitions in polymers by a multifrequency modulated dsc technique <\/li>\n<li><strong>Autor:<\/strong>\u00a0 Iria Fraga Rivas <\/li>\n<li><strong>Universidad:<\/strong>\u00a0 Polit\u00e9cnica de catalunya<\/li>\n<li><strong>Fecha de lectura de la tesis:<\/strong>\u00a0 26\/02\/2010<\/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>John M. Hutchinson<\/li>\n<\/ul>\n<\/li>\n<li><strong>Tribunal<\/strong>\n<ul>\n<li>Presidente del tribunal: jiri Malek <\/li>\n<li>Mar\u00eda Villanueva lopez (vocal)<\/li>\n<li>Juan  Jos\u00e9 Su\u00f1ol mart\u00ednez (vocal)<\/li>\n<li>xavier Ramis Juan (vocal)<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Tesis doctoral de Iria Fraga Rivas Differential scanning calorimetry (dsc) is one of the most widely used thermal analysis techniques [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""}},"footnotes":""},"categories":[11975,3079,15596,2793],"tags":[202950,191650,202951,194242,49381,15907],"class_list":["post-99449","post","type-post","status-publish","format-standard","hentry","category-analisis-de-polimeros","category-fisica-de-polimeros","category-politecnica-de-catalunya","category-termodinamica","tag-iria-fraga-rivas","tag-jiri-malek","tag-john-m-hutchinson","tag-juan-jose-sunol-Martinez","tag-maria-villanueva-lopez","tag-xavier-ramis-juan"],"_links":{"self":[{"href":"https:\/\/www.deberes.net\/tesis\/wp-json\/wp\/v2\/posts\/99449","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.deberes.net\/tesis\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.deberes.net\/tesis\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.deberes.net\/tesis\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.deberes.net\/tesis\/wp-json\/wp\/v2\/comments?post=99449"}],"version-history":[{"count":0,"href":"https:\/\/www.deberes.net\/tesis\/wp-json\/wp\/v2\/posts\/99449\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.deberes.net\/tesis\/wp-json\/wp\/v2\/media?parent=99449"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.deberes.net\/tesis\/wp-json\/wp\/v2\/categories?post=99449"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.deberes.net\/tesis\/wp-json\/wp\/v2\/tags?post=99449"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}