Development of a fire-proof coating containing silica for polystyrene

Abstract

The possibility of applying a silica-containing coating to the surface of XPS extruded polystyrene foam, which is characterized by a high degree of flammability, was evaluated. The effect of the content and concentration (11, 22, 44 and 85 %) of orthophosphate acid on the optical properties of silicic acid sols obtained by the exchange reaction between aqueous solutions of liquid glass and acetic acid was studied. The fact of incorporation of orthophosphate acid into the gel structure was confirmed by the results of acid-base titration with a sodium hydroxide solution of the intermicellar liquid isolated as a result of gel syneresis. Using an optical microscope, the structure of the polystyrene film coating after treatment with orthophosphate and sulfuric acid solutions was investigated. In both cases, the effect of an increase in the pore area and a general increase in the looseness of the surface was noted, which can help reduce its hydrophobicity and improve adhesion to the coating. The increase in hydrophilicity of the surfaces of polystyrene films after treatment with acids was also confirmed by the flatter, non-spherical shape of the drops of the composition on them. The structure of the obtained coatings on polystyrene films was analyzed. The similarity of the directions of the cracks in the case of treatment of the films with solutions of both acids was noted, and an assumption was made about the presence of uniform deformation stresses during gel shrinkage. A microscopic study of coatings on the surface of extruded polystyrene foam was conducted, and a positive effect of orthophosphate acid on the density of their structure was established. It was determined that the optimal solution for obtaining a uniform coating is the modification of the sol with the help of a 22 % solution of orthophosphate acid. Schemes of the interaction of the silica coating and the polystyrene base in cases of electrostatic interaction and in the case of the formation of covalent bonds between the coating and the polystyrene surface are proposed.