Curing Stages of Ceramic Coatings
Ceramic coatings are meant to provide an additional layer of protection for your paint, a film derived from a reaction between an oligomer, a catalyst, and humidity (water).
A chemical explanation summary:
The coating has a SiO2 ceramic matrix that includes the condensation product of hydrolyzed alkoxysilane and a colloidal silica sol.
Ceramic coating materials material has two main components of silicon dioxide: One is silica sol which is pure SiO2, another is an organoalkoxysilane which is an organic-inorganic hybrid material.
Both materials can make strong chemical bond from the chemical reaction, condensation. (ORX ′ )X 4−x (ORX′)X4−x groups are hydrolyzed with water and then make condensation with silica sol and each other.
The ceramic coating is applied by a sol-gel process. Two kinds of hydrophobic organic compounds make a chemical bond with the silica ceramic network or matrix and exist in the ceramic structure at a stable state.
The main matrix is composed of a network of silica formed by the chemical reaction or condensation of colloidal silica sol and an organoalkoxysilane such as MTMS (methyltrimethoxysilane).
The surface of colloidal silica is coated by organoalkoxysilanes, in other words, hydrolyzed organoalkoxysilane make a thin layer or coating on the silica surface as a result of the condensation reaction with the hydroxyl groups of the silica surface.
The phrase “nano-ceramic” is often said when referring to SiO2 coatings, which are only the Ceramics. The Nano materials used in coatings usually contain Silanes and Polysiloxanes as hydrophobic agents.
The Ceramic molecules are formed in a non-amorphic structure, which gives the coating very high flexibility features, compared to regular glass.
The Silanes (SiH3) are nano molecules while Siloxanes are micro molecules, in addition, Siloxanes are bonded into the ceramic structure of the coating while Silanes are not.
Siloxanes are less sensitive to water spots, whiles Silanes require a topcoat in order to prevent them from reacting with calcium and make “water-spots”.
That is the reason why topcoat, in general, are often made from Functional-Siloxanes and rather from Silanes
Application tips and guidelines:
The curing time of a ceramic coating depends allot on the amount of catalyst add the formula and the humidity rate of the environment.
As written in the chemical explanation, the coating reacts with water at its initial curing stage in order to form the SiO2 molecules, therefore, at the leveling stage of a ceramic coating (right after application), it is possible to use a damp or slightly humid towel in order to properly level the coating the vehicle’s surface without the fear of hurting the coating or making water-spots. If you chose to use a damp towel, It’s recommended to do so right after the spreading of the ceramic coating on the surface – the buffing will be much easier, and there is no risk of hurting the ceramic coating as long as the coating is fresh and it hasn’t reached the tack-free stage.
Once the coating reaches the tack-free stage, means that the polysilazane groups are fully hydrolyzed with water and the coating is dry to the touch, do not get the surface wet again for at least 7 days.
The hydrolysis of the silica leaves some the catalyst is still active, therefore can slowly react with humidity and make the entire surface become hazy white, some are confusing it water-spots – these are white reaction areas of the catalyst with water.
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