Catalysed epoxy-sebacic acid vitrimers: cure kinetics and their potential for sustainability of crosslinked polymers

Abstract

The development of more sustainable polymers has become a necessity due to the current environmental impact of traditional polymers. The use of thermoset polymers has led to issues regarding their sustainability (not recyclable, healable, or reprocessable). Among those thermosets, epoxy is one of the leading polymers for high-end applications. Vitrimer materials have proved to be an excellent candidate to increase the sustainability of epoxy-based polymers as they exhibit similar properties to the original epoxy network they are derived from, but also have the capability to be reprocessed, healed and recycled. Despite the vast literature available on vitrimer materials, the complete sustainable potential of catalysed epoxy vitrimers and their polymerisation mechanisms has yet to be fully exploited and has driven the current project towards three distinct routes. First, this research explores the possibility to use a simple and scalable manufacture method to understand the polymerisation mechanism of an epoxy-sebacic acid vitrimer system. The different mechanisms of catalysed polymerisation for off-stoichiometric formulations are used to tune the final thermomechanical properties of the final polymer without drastic changes in the manufacture process. It also explores the limitations of this method to obtain vitrimer or vitrimer-like materials. Second, the increasing interest of nanotechnology, and more accurately graphene nanoparticles as reinforcements, has also risen concerns about their use in traditional thermosets. Usually difficult to separate from the thermoset matrix, vitrimers show the possibility to be dissolved in mild conditions. Therefore, the extraction and recovery of nanoparticles is the second explored point of this project. After assessment of the effect of nanoparticles addition into the vitrimer system, they are successfully recovered with few structural changed observed. Finally, various sustainable options are available to replace traditional epoxy or hardener monomers. However, a lot remains unexplored in the case of catalysts. This project shows the possibility to use lipases as sustainable biocatalysts for the polymerisation of epoxy-sebacic acid network. This polymer exhibits vitrimer properties at high temperatures (> 185°C) but also a remarkable supramolecular behaviour below 100°C.

Date of Award	1 Aug 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Constantinos Soutis (Supervisor) & Jonny Blaker (Supervisor)