Effect of mixed sol-gel precursors on inorganic-organic polyurethane hybrid thermosets: DOE study

A series of organic-inorganic hybrid coatings were formulated using cyclohexane based polyester polyol reacting with hexamethylene diisocyanate isocyanurate (3HDI) as the organic polyurethane phase. The inorganic phase consisted of various sol-gel precursors [Tetraethyl orthosilicate (TEOS), Titanium(IV) isopropoxide (TIP), Zirconium(IV) propoxide (ZAP)]. 3-aminopropyltriethoxysilane (APTES) mono-functionalized HDI (APTES-3HDI) was used as a coupling agent to link the organic phase and inorganic phase. The hetero-bonded siliconoxygen-metal (Si-O-Metal) colloids resulting from a mixed species of sol-gel precursors within hybrids were formed and confirmed by Solid State NMR. The effect of mixed sol-gel precursors was investigated and optimized using design of experiments (DOES) for the viscoelastic, mechanical, and coating properties. The synergistic effect of eliminating the phase separation and enhancing coating properties were observed from small angle X-ray scattering (SAXS) and scanning electron microscopy (SEM).