Use of covalent dynamic networks as binders on epoxy-based carbon fiber composites: Effect on properties, processing, and recyclability

Composites are gaining widespread market interest due to their outstanding mechanical properties and light weight. However, this growth is hindered by the lack of sustainable recycling solutions. This research aims to integrate reversible chemistries to advanced carbon fiber-reinforced composite materials for recycling in a so-called eco-design, circular approach. Diene and dienophile reactions are generated at the surface of the carbon fiber allowing a bond–debond interaction with the epoxy matrix. The application of the Diels–Alder adduct on the fiber modifies its polarity and structure. This research assesses a biobased and synthetic epoxy equivalent and demonstrates that this newly developed interphase chemistry has a direct impact on the crosslinking efficiency of the resin, as well as on their interlaminar properties. Furthermore, it has been observed that depending on the type of resin, these changes can have differing impacts on final properties of the composite, reducing the crosslinking density up to 50% in some modifications while in others the T_g remains constant.