Self-healing of chemically bonded hybrid silica/epoxy for steel coating

New amino-functionalized smart silica composites and nanoparticles were prepared from hydrolyzing microgel based on N-isopropylacrylamide-co-vinyltrimethoxysilane (NIPAM-VTS) with tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTS). The chemical structure, morphology, particle sizes, and thermal stability were evaluated and proved that the amino group contents were increased on the surfaces of silica composites more than that modified after calcination at 700 degrees C. The amino-functionalized calcined silica nanoparticles and NIPAM-VTS-polysiloxane were found to show better dispersion capability than silica NPs particles existed in the epoxy hybrid coatings. The amino-functionalized hybrid silica epoxy coatings were found to be much superior in the adhesion, mechanical testing and corrosion protection over those of hybrid materials without amino-functionalization. The amino-functionalized NIPAM-VTS-polysiloxane shows new self-healing performance when blended with epoxy matrix at weight content equals or above 6 Wt. % after exposure to salt spray humidity of seawater. The self-healing performance may have probably resulted from the salt sensitivity of amino-functionalized NIPAM-VTS-polysiloxane composite and enhancement of the adhesion strength due to the formation of Fe- O Si and Fe NH --- Si covalent bonds at the interface of epoxy coating.