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Improving Glass Transition Temperature and Toughness of Epoxy Adhesives by a Complex Room-Temperature Curing System by Changing the Stoichiometry
The glass transition temperature (Tg) of room-temperature curing epoxy adhesives is limited by the temperature used during curing. It is already known that the excess of epoxy groups can undergo a homopolymerization reaction initiated by tertiary amines at elevated temperatures, resulting in an incr...
Autores principales: | , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
MDPI
2023
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9864282/ https://www.ncbi.nlm.nih.gov/pubmed/36679133 http://dx.doi.org/10.3390/polym15020252 |
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author | Ruíz de Azúa, Oiane Agulló, Núria Arbusà, Jordi Borrós, Salvador |
author_facet | Ruíz de Azúa, Oiane Agulló, Núria Arbusà, Jordi Borrós, Salvador |
author_sort | Ruíz de Azúa, Oiane |
collection | PubMed |
description | The glass transition temperature (Tg) of room-temperature curing epoxy adhesives is limited by the temperature used during curing. It is already known that the excess of epoxy groups can undergo a homopolymerization reaction initiated by tertiary amines at elevated temperatures, resulting in an increase in Tg. However, there is no evidence of this reaction occurring at room temperature. In the present work, the influence of formulation stoichiometry on Tg and mechanical properties was investigated. Dynamomechanical, rheological and mechanical properties of epoxy adhesives were determined by DSC, DMA, rheometer and tensile and shear strength testing. It has been probed that an excess of epoxy resin combined with a complex curing system composed of a primary amine, a polymercaptan and a tertiary amine leads to an increase in Tg up to 70 °C due to the homopolymerization reaction that takes place at room temperature. However, as the excess of epoxy resin is increased, gel time becomes slower. Regarding mechanical properties, it has been proven that an excess of epoxy resin provides a tighter and tougher material but maintains flexibility of the stoichiometric formulation, which is meant to enhance the resistance to impact-type forces, thermal shock and thermal cycling. |
format | Online Article Text |
id | pubmed-9864282 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2023 |
publisher | MDPI |
record_format | MEDLINE/PubMed |
spelling | pubmed-98642822023-01-22 Improving Glass Transition Temperature and Toughness of Epoxy Adhesives by a Complex Room-Temperature Curing System by Changing the Stoichiometry Ruíz de Azúa, Oiane Agulló, Núria Arbusà, Jordi Borrós, Salvador Polymers (Basel) Article The glass transition temperature (Tg) of room-temperature curing epoxy adhesives is limited by the temperature used during curing. It is already known that the excess of epoxy groups can undergo a homopolymerization reaction initiated by tertiary amines at elevated temperatures, resulting in an increase in Tg. However, there is no evidence of this reaction occurring at room temperature. In the present work, the influence of formulation stoichiometry on Tg and mechanical properties was investigated. Dynamomechanical, rheological and mechanical properties of epoxy adhesives were determined by DSC, DMA, rheometer and tensile and shear strength testing. It has been probed that an excess of epoxy resin combined with a complex curing system composed of a primary amine, a polymercaptan and a tertiary amine leads to an increase in Tg up to 70 °C due to the homopolymerization reaction that takes place at room temperature. However, as the excess of epoxy resin is increased, gel time becomes slower. Regarding mechanical properties, it has been proven that an excess of epoxy resin provides a tighter and tougher material but maintains flexibility of the stoichiometric formulation, which is meant to enhance the resistance to impact-type forces, thermal shock and thermal cycling. MDPI 2023-01-04 /pmc/articles/PMC9864282/ /pubmed/36679133 http://dx.doi.org/10.3390/polym15020252 Text en © 2023 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). |
spellingShingle | Article Ruíz de Azúa, Oiane Agulló, Núria Arbusà, Jordi Borrós, Salvador Improving Glass Transition Temperature and Toughness of Epoxy Adhesives by a Complex Room-Temperature Curing System by Changing the Stoichiometry |
title | Improving Glass Transition Temperature and Toughness of Epoxy Adhesives by a Complex Room-Temperature Curing System by Changing the Stoichiometry |
title_full | Improving Glass Transition Temperature and Toughness of Epoxy Adhesives by a Complex Room-Temperature Curing System by Changing the Stoichiometry |
title_fullStr | Improving Glass Transition Temperature and Toughness of Epoxy Adhesives by a Complex Room-Temperature Curing System by Changing the Stoichiometry |
title_full_unstemmed | Improving Glass Transition Temperature and Toughness of Epoxy Adhesives by a Complex Room-Temperature Curing System by Changing the Stoichiometry |
title_short | Improving Glass Transition Temperature and Toughness of Epoxy Adhesives by a Complex Room-Temperature Curing System by Changing the Stoichiometry |
title_sort | improving glass transition temperature and toughness of epoxy adhesives by a complex room-temperature curing system by changing the stoichiometry |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9864282/ https://www.ncbi.nlm.nih.gov/pubmed/36679133 http://dx.doi.org/10.3390/polym15020252 |
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