Bio‐Based Degradable Thermoplastic Polyurethane/Cellulose Nanocrystals Nanocomposites With Superior Mechanical and Thermal Properties by Various Interfacial Compatibility Regulating Strategies

Cellulose nanocrystals (CNC), as a natural polymeric material, possess excellent mechanical strength and biocompatibility, making them an ideal nano‐reinforcing phase for the manufacture of environmentally friendly polymer composites. In this study, to improve the dispersion and interfacial bonding strength of CNC in the thermoplastic polyurethane (TPU), silane coupling agent, short‐chain urethane linkers, and short‐chain urea‐ester linkers were grafted onto the CNC surface to produce the functional fillers K‐CNC, CO‐CNC, and NH‐CNC. TPU nanocomposites with varying CNC loadings were then prepared by solution blending with a self‐made TPU matrix. X‐ray diffraction and Fourier transform infrared spectroscopy analyses confirmed strong interactions between the nanocellulose and the TPU, even affecting the TPU crystalline structure. Furthermore, stronger hydrogen bonding between CO‐CNC/NH‐CNC and TPU further improved interfacial adhesion and filler dispersion, significantly improving the thermal and mechanical properties of the nanocomposites. The TPU nanocomposites prepared with 5 wt% CO‐CNC exhibited the best mechanical properties, with a tensile strength of 41.4 ± 1.8 MPa, an elongation at break of 1317.8% ± 102.6%, and a fracture toughness of 301.3 ± 33.9 MJ/m 3 . Finally, after immersion in 1 M HCl at 45°C for 7 days, all nanocomposites exhibited a mass loss of over 65%, demonstrating rapid degradability.