High-Performance Self-Lubricating Epoxy Composites Using Bioinspired Silica Microcapsules: Interfacial Engineering and Tribological Performance

This study introduces high-performance self-lubricating epoxy composites incorporating bioinspired silica microcapsules. Fabricated via optimized oil-in-water emulsion, the microcapsules (8–22 μm diameter, 0.5–0.6 μm shell thickness) demonstrate excellent thermal stability (200°C for 1 h) and high polyalphaolefin (PAO) encapsulation efficiency. At 5.0 wt% loading, the composite achieves outstanding tribological performance with an 89% reduction in both friction coefficient (from 0.56 to 0.08) and wear rate (from 120 to 13 × 10 −6 mm 3 /Nm) under 5 N load, while retaining 85% of compressive strength. Microstructural analysis confirms uniform microcapsule dispersion and strong interfacial adhesion with the epoxy matrix. The composite exhibits a unique stress-responsive lubrication mechanism where mechanical triggers cause microcapsule rupture, releasing PAO to form continuous lubricating films combined with silica fragments. This dynamic process is quantitatively described by a conceptual kinetic framework model that accounts for stress-dependent rupture and lubricant entrainment. The excellent balance of tribological properties and mechanical integrity demonstrated under laboratory conditions makes these composites promising candidates for further investigation toward demanding applications.