Wood Fiber-Reinforced Soybean Oil-Based Vitrimer Composites with Enhanced Mechanical Properties and Heat Resistance

Biobased vitrimers derived from epoxidized vegetable oil (EVO) hold considerable promise for sustainable applications, yet their practical viability is severely constrained by insufficient mechanical strength and poor heat resistance, both inherent to their flexible aliphatic backbones. To overcome these shortcomings, we propose constructing a natural fiber network within the vitrimer matrix to enhance rigidity and suppress chain mobility, thereby retarding dynamic exchange kinetics for simultaneous mechanical performance and heat resistance reinforcement. We validated this strategy by incorporating wood fibers (WFs, 10–70 wt %) into an epoxidized soybean oil-based imine vitrimer via a solvent-free melt-mixing/compression-molding route. The neat vitrimer exhibited excellent reprocessability (>90% tensile property retention after three cycles). WF incorporation dramatically improved mechanical performance (tensile modulus + 201%, tensile strength + 25%) and heat resistance—the rubbery storage modulus at 60 °C increased from 6.6 to 920.3 MPa, and composites with ≥30 wt % WF resisted fracture under 80 °C/200 g loading. Satisfactory reprocessability persisted even at 50 wt % WF content. Collectively, the natural fiber network effectively resolves the mechanical and thermal bottlenecks of EVO-based vitrimers without compromising thermal recyclability, providing a scalable route to high-performance, biobased, and recyclable composites.