Alkoxysilane Oligomer Modified Epoxide Primers

Telechelic resins with reactive end groups (epoxy phosphate and epoxy ester) were synthesized using bisphenol-A (BPA) epoxide. The bisphenol-A based epoxide, the epoxy phosphate, and the epoxy ester were all modified with tetraethylorthosilicate (TEOS) oligomers, which were prepared through the hydrolysis and condensation of TEOS monomer with water under acidic condition. The epoxide/polysilicate (organic/inorganic) hybrid systems were characterized systematically, using FTIR, 1H, 13C, 31P, and 29Si NMR, and MALDI-TOF. The modified epoxides were thermally cured with a melamine-formaldehyde resin, cast on steel substrates. The coating performance of the modified epoxides was evaluated by pencil hardness, crosshatch adhesion, reverse and direct impact resistance, mandrel bending, and pull-off adhesion. Viscoelastic properties of the hybrid systems were also evaluated as a function of polysilicate content. Corrosion performance was evaluated via salt spray (fog) test for 264 h. Salt spray analysis revealed that inorganically modified epoxides provided improvement over the unmodified epoxide resins with respect to both corrosion resistance and adhesion to steel substrates