Influence of Blocked Water Borne Isocyanate Crosslinker Content on Properties of Acrylic-siloxane Composite Coating

Silicone/SiO₂ organic-inorganic hybrid sols were prepared by means of sol-gel method and through hydrolysis-polycondensation reaction from following reagents: tetraethyl orthosilicate (TEOS) as inorganic precursor, 3-methacryloxypropyltrimethoxysilane (KH-570), methyl triethoxysilane (MTES) and diphenyl dimethoxy silane (DDS) as organic precursor and acetic acid as catalysts. An acrylic-silicone composite coating was prepared using a hybrid sol modified aqueous acrylic resin. The effect of blocked water borne isocyanate content on the performance of composite coatings was investigated. The results show that the organosilicon/SiO₂ hybrid sol was successfully grafted onto the waterborne acrylic resin molecule, and the isocyanate smoothly crosslinked with the hydroxyl group. As the content of the blocked aqueous isocyanate increased, the hardness, impact strength and adhesion of the coating first increased and then decreased. When the mass fraction of the blocked aqueous isocyanate was 8%, the coating had good comprehensive physical properties and corrosion resistance.