Bio-based Cyclic Acetal Epoxy Vitrimer Upcycling: From Composite Matrix to Interface

Epoxy resins, extensively employed as the polymer matrix in composites, face significant environmental challenges owing to their non-degradability. While incorporating dynamic acetal bonds offers promise, current acetal epoxies suffer from low modulus, poor thermal stability, and unoptimized degradation kinetics/performance balance. Furthermore, upcycling their degradation products yields only low-value additives with compromised properties. We present a bio-based epoxy vitrimer reconciling performance and circularity. Synthesized from vanillin and sorbitol, its key innovation is integrating multicyclic acetal motifs within the network. This vitrimer overcomes traditional limitations, achieving a high tensile modulus (3.63 GPa) and thermal stability (T d5 : 331 °C), suitable for demanding applications. Its molecular design enables ultrafast degradation (within 6 min, 65 °C) in diluted acid, facilitated by high-density labile cyclic acetal crosslinks. Crucially, the aldehyde/hydroxyl-rich degradation products are upcycled into high-performance sizing agents for carbon fiber composites. These agents achieve interfacial shear strengths of 70-80 MPa, matching industrial standards and resolving the acetal-epoxy upcycling challenge. This work establishes a scalable, sustainable framework for high-performance polymers, enabling efficient composite recycling and aligning industrial needs with circular economy principles.