Synthesis of aqueous highly branched silica sol as underlying crosslinker for corrosion protection

The aqueous hybrid silica sol was prepared by GPTMS and TEOS through sol-gel process. The GPTMS as water based modifier improved the stability of the aqueous silica sol. The highly branched structure of the aqueous sol was confirmed by Raman spectra and GPC. Using a sol-gel process these aqueous silica sols were incorporated into waterborne polyurethane (WPU). Si-29 NMR spectra detected a high crosslinked polysiloxane in composites and connection between silica sol and silanes endcapping WPU (PUS). Dynamic mechanical properties, water absorption, transparence of the composite films have been studied. Scanning electron microscopy (SEM) showed the distribution state of polysiloxane network in composites. It was found that the distribution state of polysiloxane could be greatly influenced by the chemical interaction between PUS and silica sol. The composites had been applied in anti-corrosion coatings. Salt spray test indicated that corrosion resistance of composites had been related to the amount of Si-OH groups.