Dense network formation in epoxy composites via hyperbranched polyester-mediated crosslinking: A route to enhanced toughness and corrosion resistance

Aiming at the problems of poor toughness, insufficient mechanical properties and bad long-term anticorrosion effect of epoxy resin coatings, a series of chemically cross-linked composite epoxy coatings were prepared in this work. The composite coating is formed by chemical bonding of aminated SiO 2 @TiO 2 particles, carboxylate-blocked hyperbranched polyester (HBPE-COOH) and TDI-modified E44 epoxy (TDI-E44). HBPE-COOH has a wealth of active sites and soft chain segments, which as an intermediate linker not only improves the bonding efficiency of the inorganic filler and the organic coating network, but also increases the flexibility of the composite coating. The adhesion strength of composite coating to the metal substrate is as high as 18.52 MPa, which ensures coating will not come off under seawater washing. The impact strength of the coating was 78 Kg·cm and no breakage occurred even when the coatings were curled on a 1 mm rod. The composite coating exhibits excellent corrosion resistance, and its impedance value remains above 1.0 × 10 9  Ω·cm 2 after 720 h of immersion in seawater, which is three orders of magnitude higher than that of the conventional epoxy resin. This high-density structure through chemical cross-linking makes epoxy resins as superior anti-corrosion coatings for marine applications.