Co-binder in Silicate Paints

In silicate paints potassium sihcate is the most commonly used binder. By replacing a portion of the potassiiun sihcate by a glycerolpropylsilyl-modified silica dispersion it is possible to obtain sihcate paints with improved properties, e.g.. 

A certain amount of potassium sificate in the binder is necessary in order to have good film properties since colloidal silica by itself is not film forming. In addition, a high pH enables the reaction between sificate species and calcium to form calcium sificate, which is almost insoluble in water and thus contributes to the water resistance of the sificate paint [67]. 

System Silicate paint 20 parts silicate binder of 100 parts paint formulation Absorbed water Volume [mL] after 6 hours 

However, when replacing two-thirds of the potassium sihcate, the resulting DPU resistance was dramahcally improved. The reason for this can be that on a nanoscale it takes a minimum amount of silica nanoparticles to substantially cover/modify the surface of the pigment and fillers, micron-sized particles, in the silicate paint. Unless the surface of the silicate film is completely protected by a thin layer of glycerolpropyl-modi-fied silica nanoparticles, dirt particles can be adsorbed on the unprotected parts of the surfaces in the sihcate paint film. In addition, stress forces during the paint drying process were 

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