A water-free route to porous materials via cryoextraction and supercritical drying

In this study a novel process combining freezing, cryoextraction and supercritical drying for producing porous materials is developed. The process consists of three main steps: first of all, freezing a polymer/DMSO solution at −28 °C to obtain a monolith. Second step is solvent exchange with EtOH at...

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Detalhes bibliográficos
Autor: Castedo Hernández, Cecilia
Formato: tesis de maestría
Fecha de publicación:2021
País:España
Recursos:Universidad de Valladolid
Repositorio:UVaDOC. Repositorio Documental de la Universidad de Valladolid
OAI Identifier:oai:uvadoc.uva.es:10324/47143
Acesso em linha:https://uvadoc.uva.es/handle/10324/47143
Access Level:acceso abierto
Palavra-chave:Aerogel
Preparación route
Polvmer
Supercritical drving
2206.10 Polímeros
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spelling A water-free route to porous materials via cryoextraction and supercritical dryingCastedo Hernández, CeciliaAerogelPreparación routePolvmerSupercritical drving2206.10 PolímerosIn this study a novel process combining freezing, cryoextraction and supercritical drying for producing porous materials is developed. The process consists of three main steps: first of all, freezing a polymer/DMSO solution at −28 °C to obtain a monolith. Second step is solvent exchange with EtOH at −28 °C to extract DMSO crystals, obtaining an alcogel at the end of this process. The last part of the process is drying the alcogel with scCO2 at 120 bar and 50 °C for 3 h. The method has been used for the production of polyacrylonitrile (PAN) aerogels, it is demonstrated that for this material a high quality aerogel is obtained at 5 wt % volumetric shrinkage 36.8 6.1 %, porosity is 93.5 0.6 % and 119 18m2 g−1 of specific surface area (SSA). In addition to PAN, other polymers such as poly(vinyl alcohol) (PVA) and agar-agar and their combination with PAN are tested. Pure PVA aerogels show the higgest value of SSA at 7.5 wt % of 107 15m2 g−1. Both combinations result in a aerogel with worse quality than pure PAN. In particular, porosity and linear shrinkage experimented by PAN/PVA aerogels have a exponential relation with PVA concentration. In addition to standard conditions, liquid nitrogen at −196 °C is used as a freezing agent obtaining aerogels with lower SSA that lack physical integrity. However, whereas in conventional freezing at −28 °C directional freezing is observed, more pronounced with the decrease in concentration, for aerogels frozen at −196 °C non-hierarchical pore structures are found. Generally speaking, it has been observed that lower concentrations leave more space for DMSO crystals to grow due to looser arrangement of polymer chains. At the same time, pore walls become thinner making the network weaker leading to higher shrinkage.En el trabajo se ha desarrollado una nueva ruta, exenta de agua, para la preparación de materiales porosos a partir de polímeros que no pueden ser utilizados en la ruta convencional de producción de aerogeles. La nueva ruta está compuesta por cuatro etapas: disolución del polímero en DMSO, posteriormente congelación a -28º C, extracción del disolvente con etanol a baja temperatura- 28º c y secado supercrítico mediante CO2 a 120 bar y 50º CDepartamento de Ingeniería Química y Tecnología del Medio AmbienteHamburg University of TechnologyMáster en Ingeniería QuímicaPavel GurikovSmirnova, IrinaCocero Alonso, María JoséUniversidad de Valladolid. Escuela de Ingenierías Industriales2021info:eu-repo/semantics/masterThesisapplication/pdfhttps://uvadoc.uva.es/handle/10324/47143reponame:UVaDOC. Repositorio Documental de la Universidad de Valladolidinstname:Universidad de ValladolidInglésinfo:eu-repo/semantics/openAccesshttp://creativecommons.org/licenses/by-nc-nd/4.0/oai:uvadoc.uva.es:10324/471432026-06-13T12:44:47Z
dc.title.none.fl_str_mv A water-free route to porous materials via cryoextraction and supercritical drying
title A water-free route to porous materials via cryoextraction and supercritical drying
spellingShingle A water-free route to porous materials via cryoextraction and supercritical drying
Castedo Hernández, Cecilia
Aerogel
Preparación route
Polvmer
Supercritical drving
2206.10 Polímeros
title_short A water-free route to porous materials via cryoextraction and supercritical drying
title_full A water-free route to porous materials via cryoextraction and supercritical drying
title_fullStr A water-free route to porous materials via cryoextraction and supercritical drying
title_full_unstemmed A water-free route to porous materials via cryoextraction and supercritical drying
title_sort A water-free route to porous materials via cryoextraction and supercritical drying
dc.creator.none.fl_str_mv Castedo Hernández, Cecilia
author Castedo Hernández, Cecilia
author_facet Castedo Hernández, Cecilia
author_role author
dc.contributor.none.fl_str_mv Pavel Gurikov
Smirnova, Irina
Cocero Alonso, María José
Universidad de Valladolid. Escuela de Ingenierías Industriales
dc.subject.none.fl_str_mv Aerogel
Preparación route
Polvmer
Supercritical drving
2206.10 Polímeros
topic Aerogel
Preparación route
Polvmer
Supercritical drving
2206.10 Polímeros
description In this study a novel process combining freezing, cryoextraction and supercritical drying for producing porous materials is developed. The process consists of three main steps: first of all, freezing a polymer/DMSO solution at −28 °C to obtain a monolith. Second step is solvent exchange with EtOH at −28 °C to extract DMSO crystals, obtaining an alcogel at the end of this process. The last part of the process is drying the alcogel with scCO2 at 120 bar and 50 °C for 3 h. The method has been used for the production of polyacrylonitrile (PAN) aerogels, it is demonstrated that for this material a high quality aerogel is obtained at 5 wt % volumetric shrinkage 36.8 6.1 %, porosity is 93.5 0.6 % and 119 18m2 g−1 of specific surface area (SSA). In addition to PAN, other polymers such as poly(vinyl alcohol) (PVA) and agar-agar and their combination with PAN are tested. Pure PVA aerogels show the higgest value of SSA at 7.5 wt % of 107 15m2 g−1. Both combinations result in a aerogel with worse quality than pure PAN. In particular, porosity and linear shrinkage experimented by PAN/PVA aerogels have a exponential relation with PVA concentration. In addition to standard conditions, liquid nitrogen at −196 °C is used as a freezing agent obtaining aerogels with lower SSA that lack physical integrity. However, whereas in conventional freezing at −28 °C directional freezing is observed, more pronounced with the decrease in concentration, for aerogels frozen at −196 °C non-hierarchical pore structures are found. Generally speaking, it has been observed that lower concentrations leave more space for DMSO crystals to grow due to looser arrangement of polymer chains. At the same time, pore walls become thinner making the network weaker leading to higher shrinkage.
publishDate 2021
dc.date.none.fl_str_mv 2021
dc.type.none.fl_str_mv info:eu-repo/semantics/masterThesis
format masterThesis
dc.identifier.none.fl_str_mv https://uvadoc.uva.es/handle/10324/47143
url https://uvadoc.uva.es/handle/10324/47143
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
eu_rights_str_mv openAccess
rights_invalid_str_mv http://creativecommons.org/licenses/by-nc-nd/4.0/
dc.format.none.fl_str_mv application/pdf
dc.source.none.fl_str_mv reponame:UVaDOC. Repositorio Documental de la Universidad de Valladolid
instname:Universidad de Valladolid
instname_str Universidad de Valladolid
reponame_str UVaDOC. Repositorio Documental de la Universidad de Valladolid
collection UVaDOC. Repositorio Documental de la Universidad de Valladolid
repository.name.fl_str_mv
repository.mail.fl_str_mv
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