Enhanced Mechanical and Thermal Properties of Transparent TPU Film Composites Based on Surface Modified Acid Activated Sepiolite Nanofibers

To tackle the issue of interfacial incompatibility between hydrophilic acid-activated sepiolite nanofibers (A-SEP) and hydrophobic thermoplastic polyurethane (TPU) matrices, this study utilizes methyl trimethoxysilane (MTMS) to perform surface hydrophobization modification on A-SEP. By silane coupling, hydrophobic methyl groups (  CH 3 ) are introduced to improve interfacial compatibility. MTMS modified-acid-activated sepiolite nanofibers/TPU (MSNF/TPU) nanocomposite films are prepared using the solution casting method, and systematic characterization reveals that: the mechanical properties of the modified composites (tensile strength, elongation at break, Young's modulus) are significantly enhanced, thermal stability (decomposition temperature, residual carbon rate) is improved, and the glass transition temperature ( T g ) is adjustable. The transparency in the visible light spectrum is positively correlated with the state of fiber dispersion. This work offers a scalable interfacial engineering strategy for clay mineral-reinforced polymer composites. Graphical Incorporation of MSNF into a TPU matrix significantly enhances mechanical performance, with optimal loading (1.0 wt%) improving both tensile stress and strain at break. Compared to sepiolite-based composites (R-SEP, A-SEP), MSNF/TPU exhibits superior reinforcement. Uniform MSNF dispersion enables efficient stress transfer, yielding high-performance flexible composites for advanced applications.