High-Performance Lignin-Containing Polyurethane Elastomers with Dynamic Covalent Polymer Networks

High-performance lignin-containing polyurethane elastomers (LPUes) were successfully synthesized via partially substituting petroleum-derived polyols with depolymerized enzymatic hydrolysis lignin (DEL). The influences of DEL on the structure, thermostability, mechanical performance, and thermal reprocessability of LPUes were systematically studied. The tensile strength and toughness of PUes were significantly enhanced after the introduction of DEL, with the maximum tensile strength reaching up to 60.7 MPa and the toughness up to 263.6 MJ/m3. The enhancement for the strength and toughness was attributed to the dual cross-linking network structure and the interfacial hydrogen bonds between lignin and the PU matrix, which were demonstrated to facilitate the orientation of chain segments and lead to strain-induced crystallization and self-reinforcement. LPUes also exhibited much better elasticity than the control sample without lignin and could maintain excellent mechanical performance after being hot reprocessed.