Interfacial Bridging via IPDI-Modified Boron Carbide for Polyurea Coatings With Superior Mechanical and Anti-Corrosion Performance

Polyurea (PUA) elastomers are highly promising as protective coatings due to their exceptional energy dissipation against dynamic impact. However, conventional PUA suffers from low structural rigidity, and introducing rigid nanofillers often causes severe agglomeration and weak interfacial bonding, thereby hindering the simultaneous improvement of strength and toughness. To address these challenges, an interfacial covalent bridging strategy is developed to prepare isophorone diisocyanate (IPDI)-modified boron carbide (m-B 4 C) reinforced polyaspartic ester polyurea (PAE) coatings. Integrating IPDI-assisted mechanical exfoliation with in situ polymerization ensures uniform dispersion and robust filler-matrix covalent bonding. Nanocomposite coatings with 0.2, 0.5, and 1.0 wt% B 4 C or m-B 4 C were prepared; the optimized 0.5 wt% m-B 4 C coating exhibits 27.8 MPa tensile strength, 350% elongation at break, and 37 kN/m tear strength. Notably, the impact strengths of coated aluminum alloy and epoxy substrates reach 461 and 64 kJ/m 2 , successfully overcoming the stiffness-ductility trade-off. Furthermore, the coatings demonstrate exceptional anti-corrosion capabilities, maintaining a high impedance modulus (6.3 × 10 6 Ω cm 2 ) after 14 days in NaCl solution and remarkable rust resistance during 100 h of salt spray testing. These findings elucidate the synergistic energy dissipation and physical barrier mechanism of the rigid-particle/flexible-matrix architecture, providing a pathway toward designing high-performance multifunctional lightweight protective coatings.