Modified Nano-SiO2 Synergistic Carnauba Wax Reinforced Polyurethane Composite with Enhanced Hydrophobicity, Wear Resistance, and Vibration Damping for Underwater Equipment

The wear and vibration challenges of water-lubricated polymer components in mechanical systems remain critical. In this study, a polyurethane composite reinforced with modified nano-SiO2 and carnauba wax via casting (PUCW-SiO2) was developed, and its properties were explored. With merely 0.5% additive content of modified SiO2, the optimized composite of PUCW-0.5%SiO2 exhibited a low water swelling rate (0.157% after 7 days), enhanced mechanical properties (compressive elastic modulus is 410.39 MPa and compressive strength is 89.12 MPa), reduced wear loss (0.01 g in water), effective vibration damping (vibration acceleration signal is reduced to −4–4 m/s2 in a stable wear stage in a pure water environment), and sand-water environmental tolerance (average friction coefficient is 0.351, average wear loss is 0.0253 g). The improvements stem from modified SiO2 reinforcing the polyurethane matrix and synergizing with carnauba wax, facilitating the formation of a hydrophobic surface and continuous lubricating film that collectively mitigate wear and vibration.