Improvement Mechanism of Dielectric and Mechanical Properties of Organic-Polymer-Based Functional Nanocomposites via Nanofiller Interface Modification

Organic-polymer-based functional nanocomposites have outstanding application prospects in flexible electronic devices, energy storage dielectrics, microwave absorption materials and intelligent sensors due to their merits of light weight, facile processing, adjustable flexibility and excellent functional adaptability. Nevertheless, nanofillers suffer from large specific surface area and high surface energy, which inevitably cause severe agglomeration inside polymer matrices. Meanwhile, poor interfacial compatibility and abundant interfacial defects between inorganic nanofillers and organic polymer matrices severely restrict the synchronous improvement of mechanical stability and dielectric performance of composite materials. In this work, thermoplastic polyurethane (TPU) was selected as the organic polymer matrix, and montmorillonite (MMT) nanosheets served as inorganic functional nanofillers. Silane coupling agent KH-550 was adopted to modify the surface of MMT nanofillers, and TPU/MMT organic-polymer-based nanocomposites with different filler loadings were fabricated via melt blending method. The microscopic morphology, mechanical properties and dielectric performances of prepared samples were systematically characterized by scanning electron microscope (SEM), universal material testing machine and broadband dielectric spectrometer. Combined with interface polarization theory and interfacial binding energy model, the intrinsic mechanism of performance enhancement was clarified. The experimental results demonstrate that KH-550 interface modification effectively inhibits the agglomeration of MMT nanosheets in TPU matrix, and the number of interfacial cavity defects is reduced by 47.2%. When the loading content of modified MMT is 3.5 wt%, the tensile strength of composite reaches 18.03 MPa, which is 42.6% higher than that of pure TPU matrix. Meanwhile, the dielectric constant is improved to 9.87 at 1 kHz, and the dielectric loss maintains a low level of 0.032. The synchronous optimization of mechanical and dielectric performances is realized. This study clarifies the dual mechanisms of interface modification on improving interfacial compatibility and regulating interfacial polarization behavior, which provides universal theoretical references and experimental foundations for structural design and process optimization of high-performance organic-polymer-based functional nanocomposites.