Epoxy resin with exchangeable disulfide crosslinks to obtain reprocessable, repairable and recyclable fiber-reinforced thermoset composites

Abstract

Thermoset fiber-reinforced polymer composites can now be reprocessed, recycled and repaired, thanks to a dynamic epoxy resin.

Transient mechanochromism in epoxy vitrimer composites containing aromatic disulfide crosslinks

“…Very recently we developed a dynamic epoxy resin (p-EPO, Scheme 1), which was based on reversible aromatic disulfide crosslinks. 11 Due to such reversible disulfides, which were previously applied for the design of dynamic elastomeric materials, [12][13][14] the epoxy network presented a vitrimer-like behavior, 2 i.e., it showed stress relaxation at high temperatures. This permitted to successfully use the resin for the manufacturing of fiber-reinforced thermoset composites which were reprocessable, repairable and recyclable.…”

“…The preparation of such networks was performed by mixing DGEBA with the corresponding hardener followed by a curing cycle, as described previously. 11 Glass transition temperature (T g ), degradation temperature (T d ) and stress and strain at break obtained for each epoxy network are shown in Table 1. It is worth noticing that 2-AFD led to an epoxy network with lower T g .…”

Protected thiol strategies in macromolecular design

“…This is an interesting feature, especially in the development of covalent adaptable networks (CANs) [122][123][124] and more specifically vitrimers, which can exhibit self-healing capabilities [73,[125][126][127][128].…”

Dynamic Covalent Chemistry at Interfaces: Development of Tougher, Healable Composites through Stress Relaxation at the Resin–Silica Nanoparticles Interface

“…Organic nanoparticles with aggregation induced emission properties based on dynamic bonds have previously been developed. [29–31] Fiber-reinforced composites, [32] carbon nanotube composites, [33] and silica nanocomposites [34] made of a dynamic epoxy resin have been investigated. Also, transesterification-based shape memory composites based on graphene-filled vitrimers were prepared.…”

“…The interfacial DCC was employed at the composite interfaces, not only covalently bonds the resins to the filler as is often done with other filler modifications to promote adhesion between the filler and resin, but here this approach also creates composite interfaces capable of stress relaxation and dynamic bond exchange. While DCC approaches such as AFT, [14,15] Diels–Alder, [21,36] transesterification, [18] and others have been used extensively to promote healing and other desirable aspects in conventional materials, [11,32,37] the localization of a dynamic covalent bond to the interface has been little if ever explored, particularly relative to controls in which no such bond exchange is possible. The evolution of material properties including toughness, tensile strength, polymerization shrinkage stress, and the recovery of the dissipative energy in covalently cross-linked, relatively glassy, photo-polymerized thiol-ene composites was explored for both adaptive interface (AI) and passive interface (PI)-based composites.…”