CAN it work? Using hydroxyethyl acrylate or methacrylate to turn epoxy-amine thermosets into covalent adaptable network materials.
Year: 2026
Type: preprint
Abstract: Epoxy-amine thermosets can be converted into covalent adaptable networks (CANs) by adding β-aminoester-based curing agents to the formulation. This is achieved by utilizing commercially available di- or trifunctional acrylate monomers, which react with the amine component via an aza-Michael addition. Consequently, this approach is inherently scalable and holds high industrial relevance. In this study, the fundamental applicability of two commodity chemicals—namely 2-hydroxyethyl acrylate (HEA) and 2-hydroxyethyl methacrylate (HEMA)—for this purpose is investigated, aiming to provide an additional handle to mitigate the rapid viscosity increase of the formulations. Using a model epoxy resin consisting of bisphenol A diglycidyl ether (DGEBA) and 1,3-bis(aminomethyl)cyclohexane (BAC), it was demonstrated that a Lewis-base catalyst (1-methylimidazole) is necessary to incorporate the hydroxy groups of HEA and HEMA into the network. Contrary to expectations, this incorporation proceeds predominantly through a condensation reaction that liberates ethylene glycol. Finally, a formulation consisting of 1 equiv. DGEBA, 0.5 equiv. BAC, 1 equiv. HEA, and 0.025 equiv. 1-methylimidazole was found to offer a good compromise, providing both satisfactory reprocessability and a sufficiently high glass transition temperature (74 °C). Compared to a reference formulation made with a trifunctional acrylate monomer, the CAN made with HEA is characterized by a lower glass transition temperature, a similar flow activation energy, a lower storage modulus, and distinctly longer relaxation times. Both acrylate-based CAN materials aged under thermal stress, which resulted in higher storage moduli and glass transition temperatures upon reprocessing. A protocol for characterizing such modulus changes under thermal stress is suggested, consisting of performing repeated frequency sweeps for at least 1 h at temperatures slightly exceeding the maximum temperature of the stress relaxation measurements.
Source: ChemRxiv
Authors: Johanna Lang, Christian Slugovc
Institution: Graz University of Technology
Language: English
Topic: Epoxy Resin Curing Processes
Subfield: Polymers and Plastics
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7221507270