Carbon fiber-reinforced composites based on an epoxy resin containing Schiff base with intrinsic anti-flammability, good mechanical strength and recyclability

A new renewable material, comprising a Schiff base epoxy thermoset derived from furan derivatives, was successfully synthesized. This innovative material not only possesses remarkable carbon fiber recyclability but also exhibits favorable mechanical properties and flame retardancy. After being cured with the bio-based curing agent, 5,5′-methylenedifurfurylamine, the cured Schiff base epoxy thermoset exhibited an ultra-high char yield of 54% and a glass transition temperature of 207 °C. Compared to bisphenol A epoxy resin, it achieved a 100% higher yield. Furthermore, the cured Schiff base epoxy thermoset demonstrated a high storage modulus (at 30 °C) of 2695 MPa and a tensile modulus of 60 MPa, surpassing bisphenol A epoxy resin. Remarkably, the exceptional structure of the Schiff base epoxy thermoset imparted intrinsic flame retardancy, resulting in a V-0 rating in the UL-94 test. The thermoset also exhibited considerable recyclability in carbon fiber composites due to its Schiff base network. Moreover, it could be nondestructively and quickly recycled under mildly acidic conditions, enabling efficient recycling of the carbon fiber composites.