INFLUENCE OF POLYORGANOSILOXANES ON HYDROPHOBICITY AND BARRIER PROPERTIES OF POLYACRYLATE COATINGS
The influence of polyorganosiloxane resins on the wetting edge angle and barrier properties of polyacrylate coatings based on copolymer of methyl methacrylate and n-butyl methacrylate was studied. The wetting edge angle of the water coated surface determined by the lying drop method increases with an increase in the content of polyorganosiloxanes in the formulation of transparent lacquer compositions, has been shown. To determine the insulating and barrier properties of coatings applied by pneumatic spraying, an electrochemical cell filled with a 3% aqueous NaCl was formed on their surface by gluing a glass cylinder. Static tests of the electrolyte solution were carried out for 500 hours with the registration of the value of the electrical capacity. It was shown, that the electrical capacity in the electrochemical cell decreases with an increase in the content of polyorganosiloxanes in the coating, which indicates an increase in the insulating capacity of coatings formed on a steel substrate. Effect of the side chain substituent type in polyorganosiloxane macromolecules on the characteristics of polyacrylate coatings was found during the tests. In particular, the use of polyphenylsiloxane resin as a modifier allows to obtain more hydrophobic coatings with better insulating properties, reaching of a comparable wetting edge angle by using of methyl-substituted analog requires more additives of the latter. At the same time, the use of polymethylsiloxane as a hydrophobizing additive does not allow to obtain a coating with insulating properties similar to a coating containing phenyl-substituted polyorganosiloxane in the concentration range above 3%, because further introduction of the additive does not lead to any noticeable change in the value of the electrical capacity in the electrochemical cell during the electrolyte solution action test.