Sustainable-by-design biobased epoxy vitrimers and their carbon-fiber reinforced composites: Tuning reprocessability and recyclability via catalyst-controlled transesterification

In this work, an algae-derived epoxy resin (phloroglucinol triglycidyl ether) was reacted with biobased succinic and glutaric anhydrides to develop reprocessable and recyclable vitrimers. The effect on the bond exchange reaction dynamics of two different transesterification catalysts (zinc acetylacetonate, Zn(acac)2, and triazabicyclodecene, TBD) was investigated. Zn(acac)2-containing resins showed appreciable stress relaxation (10 min at 220 °C), which was further exploited to assess the material reprocessability by post-cure thermoforming, shape programming, and self-repairing experiments. The good solubility of TBD in alcohols and the ability of TBD-catalyzed resins to relax stresses at lower temperatures (30 min at 200 °C) were instead exploited for glycolysis in milder conditions. These biobased vitrimer resins were fully solvolyzed in 1,4-butanediol as OH-containing solvent to promote dynamic exchange reactions at 190 °C. Complete resin dissolution was achieved within 30 min in a solution catalyzed by TBD at 5 wt.%. A carbon-fiber reinforced composite was produced from this formulation, and its chemical recycling yielded complete fiber liberation in 1 h. Characterization of the recovered reinforcement provided appearance, mechanical properties, and thermal stability comparable to those of the virgin filaments, suggesting the possibility of implementing the recycled fibers in the fabrication of second-generation composite materials compliant with the circular economy principles.