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Polymers 2018, 10(1), 43; https://doi.org/10.3390/polym10010043

Epoxy Vitrimers: The Effect of Transesterification Reactions on the Network Structure

Institute of Materials Science and Technology (INTEMA), University of Mar del Plata and National Research Council (CONICET), Av. J. B. Justo 4302, 7600 Mar del Plata, Argentina
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Received: 29 November 2017 / Revised: 20 December 2017 / Accepted: 29 December 2017 / Published: 3 January 2018
(This article belongs to the Special Issue Thermosets)
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Abstract

Vitrimers are covalently crosslinked polymers that behave as conventional thermosets below the glass transition temperature (Tg) but can flow above a particular temperature, Tv > Tg, by bond exchange reactions. In epoxy vitrimers, transesterification reactions are responsible for their behavior at T > Tv that enables flow, thermoforming, recycling, self-healing and stress relaxation. A statistical analysis based on the fragment approach was performed to analyze the evolution of the network structure of epoxy vitrimers during transesterification reactions. An analytical solution was obtained for a formulation based on a diepoxide and a dicarboxylic acid. A numerical solution was derived for the reaction of a diepoxide with a tricarboxylic acid, as an example of the way to apply the model to polyfunctional monomers. As transesterification acts as a disproportionation reaction that converts two linear fragments (monoesters) into a terminal fragment (glycol) and a branching fragment (diester), its effect on network structure is to increase the concentration of crosslinks and pendant chains while leaving a sol fraction. Changes in the network structure of the epoxy vitrimer can take place after their synthesis, during their use at high temperatures, a fact that has to be considered in their technological applications. View Full-Text
Keywords: epoxy-acid reactions; epoxy vitrimers; fragment approach; network structure; statistical analysis; transesterification reactions epoxy-acid reactions; epoxy vitrimers; fragment approach; network structure; statistical analysis; transesterification reactions
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Altuna, F.I.; Hoppe, C.E.; Williams, R.J.J. Epoxy Vitrimers: The Effect of Transesterification Reactions on the Network Structure. Polymers 2018, 10, 43.

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