Fabrication and characterization of Fe3+ chelated tannic acid modified cellulose nanofiber reinforced waterborne polyurethane elastomers

To address the inadequate mechanical strength of conventional waterborne polyurethane (WPU) caused by hydrophilic group incorporation, alongside the agglomeration tendency of cellulose nanofibers (CNF) as reinforcing fillers, this study proposes a multiscale dynamic reinforcement strategy leveraging synergistic “metal coordination and multiple hydrogen bonding.” Fe 3+ chelated tannic acid (TA)-modified CNF (Fe 3+ /TA@CNF) was fabricated as an enhancer and incorporated with WPU via a solvent casting technique to produce modified CNF reinforced WPU elastomer composites (F x T 1 CWPU). Subsequently, composite conductive films (MXene/F x T 1 CWPU) were fabricated through MXene conductive coating. Systematic investigations were conducted on the effects of the molar ratio of Fe 3+ to TA on the microstructure, thermal stability, and mechanical properties of the F x T 1 CWPU films. Furthermore, the sensing properties of the MXene/F x T 1 CWPU films were evaluated. When the molar ratio of Fe 3+ to TA was set at 2:1, the composite film demonstrated exceptional mechanical, ultimate tensile strength (6.12 MPa) and toughness (18.67 MJ·m −3 ) increased by 652 % and 461 % compared to WPU. Subsequent cyclic tensile tests confirmed the excellent resilience and energy - dissipation capacity of the composite films. Notably, the Fe 3+ and TA coordination network gives the material excellent adhesion properties (1.23 MPa shear strength on wood surfaces). Moreover, the MXene/F x T 1 CWPU films reliably monitored human motion, showing their promise as flexible substrates for wearable electronics (The film achieved stable acquisition of electrical signals from continuous limb movements over a 15-second period and accurately identified the timing of each individual movement.). This work provides a new approach for the development of multifunctional polymer nanocomposites. • Films of waterborne polyurethane reinforced with Fe 3+ chelated TA modified CNF were prepared. • A hierarchical dynamic reinforcement strategy via metal coordination and hydrogen bonding is proposed. • The composite exhibited satisfactory thermal stability (440.97℃) and favorable adhesion (1.23 MPa). • Tensile strength and toughness were increased by 65 and 46 times. • After conductive coating, the composite film can reliably monitor human movement.