Effect of the addition of 3-glycidoxypropyltrimethoxysilane to tetraethoxyorthosilicate-based stone protective coating using n-octylamine as a catalyst

A tetraethoxyorthosilicate (TEOS)-based stone protective coating containing functional 3-glycidoxypropyltrimethoxysilane (GPTMS) has been prepared in order to reduce gel crack formation during the drying phase using n-octylamine as a catalyst. The effect of gel time and viscosity on GPTMS concentration were studied. We have demonstrated that the addition of GPTMS accelerated the gel process and improve viscosity of sol. It was found that GPTMS was chemically incorporated into the gel matrix via Si–O bonds by Fourier transform infrared spectroscopy (FTIR) analysis. Nitrogen adsorption–desorption isotherms of xerogels were measured, they showed that the pore size of xerogels decreased with the addition of GPTMS. Atomic force microscopy (AFM) showed the surface roughness increased as content of GPTMS was higher. The Scotch Tape test and the hardness values showed improvement of cohesion and consolidation ability of hybrid sol. The protective performance evaluation of the treated stones with hybrid sol indicated its acid rain resistance.