Enhanced Mechanical Performance of Silicone Rubber Using Silica-Cellulose Hybrid Nanofibers with Strong Polymer–Filler Interactions

It remains challenging to create rigid fiber networks in hydrophobic silicone rubber (SR) by using hydrophilic cellulose nanofibers (CNFs) with high interfacial compatibility for mechanical reinforcement through solvent-free processing. In this work, a silica-cellulose hybrid nanofiber (Me-SiO2/CNFs) was prepared via in situ polymerization of hydrophobic silica particles on the CNF surface using the sol–gel method, where CNFs served as a rigid template. The resulting Me-SiO2/CNFs exhibit a bead-like morphology and can be readily pulverized into the SR matrix, enabling the preparation of highly transparent nanocomposites through conventional mixing and vulcanization processes that eliminate freeze drying and mechanical grinding. With a large specific surface area (221 m2·g–1) and high aspect ratio, Me-SiO2/CNFs show strong polymer–filler interactions and form filler percolation networks. In particular, the polymer–filler interactions and energy dissipation capacity are enhanced by the entanglement of SR molecular chains with surface silica particles. Meanwhile, the internal CNF framework establishes a branched fiber network. These two synergistic mechanisms collectively improve the mechanical strength of SR nanocomposites. Notably, the tensile strength and tear strength of SR/CNF nanocomposites increased by 39.7% and 45.5%, respectively. Furthermore, the processability and synergistic reinforcement mechanisms were systematically investigated. This study provides valuable insights for implementing CNFs as a reinforcing filler in industrial applications of high-temperature vulcanized silicone rubber.