Self-Healing and Recyclable Castor Oil-Based Epoxy Vitrimer Based on Dual Dynamic Bonds of Disulfide and Ester Bonds

In order to develop a more sustainable and environmentally friendly epoxy resin, castor oil (CO)-based epoxy vitrimers based on dynamic ester bonds and disulfide bonds were prepared through epoxy-carboxylic acid, epoxy-amine, and free-radical polymerization reactions using epoxidized methacrylated castor oil as the epoxy prepolymer, glycerol methacrylate as the reactive diluent, and itaconic acid (IA) and 4,4′-dithiodiphenylamine (AFD) as the curing agents. The curing kinetics, curing degree, mechanical properties, thermal stability, and recycling characteristics of the EMCO-GMA-IA-AFD epoxy vitrimers were investigated. When the molar ratio of IA to AFD was 5:5, the EMCO-GMA-IA-AFD5:5 vitrimer exhibited a balanced comprehensive performance with a storage modulus of 1715 MPa, a tensile strength of 16.8 MPa, and a Tg of 44.6 °C. Meanwhile, the dynamic ester bonds and disulfide bonds within the system endowed the EMCO-GMA-IA-AFD vitrimer with self-healing ability and recyclability; the activation energy of reversible exchange reactions reached 89.29 kJ/mol, and the self-healing efficiency reached 94.6%. In addition, the EMCO-GMA-IA-AFD vitrimer was chemically degradable. Overall, this work provides a promising and feasible route for the preparation of sustainable CO-based epoxy with superior comprehensive properties.