Thermal-induced self-healing bio-based vitrimers: Shape memory, recyclability, degradation, and intrinsic flame retardancy

The structure of epoxy resin determines its flammable property, non-reprocessing, unrecyclable, and nondegradable, which limits their application. Thus, a novel disulfide bond-containing dynamic covalent thiol-ene crosslinked epoxy vitrimers (TECEVs) as covalently adaptable networks were synthesized. Also, the structure-property relationship of polymeric compounds was investigated. The insoluble vitrimers networks demonstrated faster stress relaxation with 107 s at 200 °C, and obtained lower activation energy between 70.52 and 110.57 kJ·mol−1. In addition, the dynamic nature of the disulfide bond allowed the damaged TECEVs to be thermal-induced self-repairing and self-healing materials with efficiencies 100% at 160 °C. It was discovered that TECEVs can be reprocessed at 160 °C with the recovery of mechanical strength above 80% and be completely decomposed in an ethanol-acid catalyst solution. Moreover, typical TECEVs can function with excellent flame retardancy and illustrated a high limit oxygen index (LOI, 27.45–28.36%), and UL-94 V-0 rating was achieved. This work could provide an efficient strategy for the synthesis of "biobased self-repairing flame retardant" networks and contribute to the development of high-performance sustainable polymers.