Catalyst-Free Covalent Adaptable Network under Internal Catalysis by Hydroxyl-Amine: Excellent Mechanical Properties, Fast Repairing and Easy Recycling

Primary author: Cheng Hao
Faculty sponsor: Jinwen Zhang

Primary college/unit: Voiland College of Engineering and Architecture
Campus: Pullman

Abstract:

Early epoxy vitrimers in the literature rely on an inequivalent epoxy/anhydride stoichiometry and a large amount of catalyst to achieve a decent transesterification rate within the crosslinked network. This design approach raises a number of concerns such as poor miscibility of the catalyst with other ingredients, poor mechanical properties owing to insufficient crosslinking, toxicity of the catalyst, etc. In this study, a hydroxyl-amine compound, triethanolamine (TEA), is incorporated as a catalytic co-curing agent to a typical BPA epoxy – cyclic anhydride curing system to give a new catalyst-free covalent adaptable network system. The hydroxyl groups and tertiary amine of TEA catalyze the curing process, and the tertiary amine and the regenerated hydroxyls in the crosslinked network accelerate dynamic transesterification. The resulting catalyst-free epoxy vitrimer exhibits high glass transition temperature (~135 °C), excellent tensile strength (~ 94 MPa) and fast repairing rate (10 min at 190 °C). In addition, the TEA-mediated epoxy vitrimer can be decomposed in ethanol at a mild condition. Use of the alcoholyzed product for coating application is also demonstrated. This work provides a solution to eliminate the performance gap between conventional epoxy and epoxy vitrimer and offers a simple recycling method of epoxy vitrimer for potential coating application.