Preparation and Characterization of Bisphenol A-Based Thermosetting Epoxies Based on Modified Lignin

Lignin is a highly abundant renewable natural resource with a unique structure, abundant reserves, and low cost. However, large-scale utilization based on lignin still remains challenging due to its heterogeneity and inhomogeneity. Herein, we report the fabrication of tunable and mechanically tough lignin-based thermosetting epoxy resins with outstanding thermal stability by optimizing epoxidation conditions and the crosslinker. The obtained lignin-based bisphenol A composites show a tensile strength of 11.5 MPa, Young's modulus of 5.0 MPa, and heat resistance index temperature (Ts) up to 160.0 °C by tailoring the dosage of epichlorohydrin. It was found that the introduction of oxirane moieties on the lignin backbone limitedly improved the interfacial compatibility of the composite. Moreover, the enhanced mechanical and thermal properties were ascribed to the incorporation of modified lignin segments into the epoxy networks and the corresponding alternation of crosslink structures. Overall, this work provides a viable pathway to produce cost-efficient biobased materials with controlled mechanical properties for adhesives and engineering plastics.