Recyclable and shape‐memory hydantoin epoxy resins based on dynamic ester‐exchanged bonds

Abstract

The permanent crosslinked network imparts chemical and mechanical stability to crosslinked elastomers, making their recycling a serious environmental issue. The decomposition products of pentaaryl diazoxide in the structure of hydantoin epoxy resin are nitrogen and carbon dioxide, and it is an environmentally friendly resin material. Here, we demonstrate a reversible covalent bonding reaction catalyzed by Zn2+ between the ester bond formed by the hydantoin epoxy resin and the acid anhydride, and construct a reversible crosslinked network structure of the environmentally friendly acid anhydride/hydantoin epoxy resin material. The strength, hardness and toughness of the cured material are greatly improved by optimizing its ratio. The ester exchange bonding can be reversible with temperature, which leads to the shape memory capability of the synthesized cured material. The cured product of HMY1 was recovered with ethylene glycol and completely dissolved at 180°C for 11 h. Ethylene glycol was volatilized at 190°C to obtain decomposed epoxy oligomer (DEO), which was added to the HMY1 resin system (the amount of DEO was 30 wt% of the total mass of the resin), and the network structure was cross‐linked to enable it to be recovered and remanufactured. Thus, this work provides a new avenue for the environmentally friendly development of recyclable, reconfigurable, and thermally adaptable shape‐memory hydantoin epoxy materials.Highlights Hydantoin epoxy resin eventually breaks down into non‐toxic CO2 and N2. Hydantoin epoxy and methyl tetrahydrophthalic anhydride form a reversible dynamic chemical bond catalyzed by Zn2+. Ethylene glycol can recover and reuse the solidified product.