Recyclable High Performance Epoxy Composites Based on Double Dynamic Carbon-Nitrogen and Disulfide Bonds

Recycling of the thermosetting resin is a big challenge due to the formation of cross-linked, three-dimensional network structures after curing. In this study, a simple mild and effective method was used to synthesize an aromatic amine curing agent containing dynamic disulfide bonds and carbon-nitrogen bonds, which is used to cure epoxy resin (E51) to obtain a degradable thermosetting material with good heat resistance and mechanical properties. The synthesized amine curing agent was characterized by FTIR and H-1 NMR, and the thermodynamic properties, degradability, and remoldability of thermosetting materials were systematically studied. The results show that the heat resistance of the materials was almost unchanged after three repeated cycles of remolding as suggested by constant glass transition and onset degradation temperature. The new curing agent produced the glass fiber reinforced thermosetting composite with a tensile strength and an interlaminar shear strength of 732 and 71 MPa, respectively. In addition, recycling of carbon fiber can be achieved using this new curing agent containing disulfide bonds and dynamic carbon-nitrogen bonds.