Silica sol inorganic polymer coatings are a recent development. The key technology in preparing this coating is removing water-soluble sodium ions from water glass using specialized methods. This is typically achieved through ion exchange, acid neutralization, water decomposition, or electrodialysis, generating an extremely fine silica ultrafine particle colloidal aqueous solution with a particle size of 580 nm (generally, emulsion particles are 800-1000 nm). The Si₂O content is 20%-30%, the Na₂O content is 0.3%, and the ratio of silica to sodium oxide is above 40%. Using this silica solution/gel as a base, pigments and various additives are combined to produce silica sol inorganic polymer coatings. When the silica solution loses water, the monomeric silicic acid gradually polymerizes into high-polymer silica gel. As water evaporates, the colloidal molecules increase in size, eventually forming a -SiO₂-O₂SiO₂- coating: IO₂SiO₂OH + HO₂SiO₂OH. Due to the low Na₂O content in the silica sol, it possesses a certain degree of film-forming and dissolving properties, exhibiting significantly better water resistance and heat resistance than organic coatings. The coating film is dense and relatively hard, does not generate static electricity, and makes it difficult for various dust particles in the air to adhere. Among architectural coatings, it has strong anti-fouling capabilities.
The fine particles have strong penetrating power into the substrate, able to penetrate deep into the substrate through capillary action, and can react with calcium hydroxide in the concrete substrate to form calcium silicate, giving the coating strong adhesion.
However, silica sol experiences significant volume shrinkage during film formation, making the coating prone to cracking. Silica sol is miscible with emulsions such as acrylates and vinyl acetate. The complementary properties of both allow for the formulation of high-performance organic-inorganic composite coatings.