Nanoparticles I suggest: Silica, Alumina, etc

Polymer: acrylic resins is good choice, however PU give much higher weather stability

Dear Dr. Besharat:

Further resistance to the scratching can be reach using some Kind of acrylic resin, as mentioned. There is commercial resin that typically contain high fraction of solids. In this sense, good material is quartz (silica), that allow a resin clear and transparent, ideal condition to application on the noble stones. See, color and texture of stone can be seen despite of resin.

The mechanism of resistance to scratch is based on addition of particle of a material with high hardness in the Mohs scale. From quartz (silica), 7th in the ranking of Mohs’ scale, strong scratch resistance can be attained with zirconia addition or synthetic diamond, 10th rank.

As a function of rate cost/benefit, quartz (silica) is classical. Another material (hardness 8 or higher) gives a resin with high resistance to scratching but also high opacity level. A priori, nanoparticles should provide further dispersion of light and some opacity by consequence.

Kind regards

Marcos Nobre

 Silica, Alumina, as nanoparticles

Polymer: acrylic resins is good choice

Hi Seyede! I do not really understand what  the nanoparticles are needed for stones antiscratch coatings . If the stones are the external elements of building structures and are not subjected to abrasion, the main mechanism of cracking in countries with harsh climates, such as Russia, are cyclic temperature changes in winter. In the presence of adsorbed water it is an atmospheric freezing of the water. If water enters the crack, then the resulting ice expands it, etc. In this case, the presence of nanoparticles in the polymer coating will not have an appreciable (and may be negative) effect on its antiscratch properties.

 Nanoparticles : Silica, Alumina, etc. 

You can also try adding graphene powder, etc

Dear Besharat

The base polymers suitable for coating nano composite synthesis is silica. Because silica nanoparticles having different morphology and surface modification were used to prepare transparent polymeric coating samples. PLS look for the attached links it will help you very good.

Best regard

http://www.sciencedirect.com/science/article/pii/S0266353813003370

http://www.google.com/patents/WO2014116511A1?cl=en

www.researchgate.net/...of_the...antiscratch_layers_on_organic_lenses

Chapter Nanoparticles: Building Blocks for Nanotechnology

Thank you all so much all of the explanations were so helpful. 

Silica, zircornia, alumina and diamond (nano)