Heat-Resistant Protective Organosilicate Coatings for Nuclear Energy
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Heat-Resistant Protective Organosilicate Coatings for Nuclear Energy G. S. Buslaeva, T. A. Kochinaa, *, L. N. Krasil’nikovaa, P. A. Milyutinaa, and O. A. Shilovaa aGrebenshchikov
Institute of Silicate Chemistry, Russian Academy of Sciences, St. Petersburg, 199034 Russia *e-mail: [email protected] Received November 11, 2019; revised February 6, 2020; accepted April 3, 2020
Abstract—A cold hardened organosilicate material for coatings with improved decontamination is developed, which obviates the need for an additional varnish layer on its surface. In terms of its physical and mechanical characteristics and heat resistance (300°C), this coating is not inferior to the currently used OS-51-03 coating. DOI: 10.1134/S1087659620040045
Hybrid organic–inorganic materials, due to their superiority in a number of properties compared to unfilled polymers, are widely used in engineering. One of the types of hybrid composites, organosilicate materials (OSM), used as coatings (OSC), adhesives, and pastes, are quite widely known [1]. Their industrial production, organized in 1960, is carried out according to TU 84-725-78. The demand for OSM is due to a combination of important technical characteristics, such as their physical-mechanical, electroinsulating, atmospheric, and heat and moisture resistant features. In this case, the heat resistance of OSM is determined not only by the composition of the polymer silicone binder but also by the quantitative ratio (С) of the latter to the hydrosilicate layered filler: the smaller С the higher the heat resistance. For example, in accordance with TU 84-725-78 for OSC, OS-82-01, OS-92-03, and OS-82-05 are dark green with heat resistance up to 500°C, they have the same silicone binder, KO-915 varnish (polymethyldimethylphenylsiloxane modified with pentaphthalic resin), and С is 0.46, 0.45, and 0.38, respectively. Admittedly, the last coating’s adhesion to the metal substrate is slightly weaker. Trying to use OSC of dark gray OS-92-05 (С = 0.19) as the coating for the electrical insulation protection of microthermocouples, did not generally lead to positive results due to the weak adhesion of the material to the substrate. Therefore, for OSC with the binder mentioned above with heat resistance up to 500°C, i.e., until the complete decarburization of the material within 2 h, the minimum value of С is probably 0.4. For OSC, as for other coatings, the presentation of the surface and the invariability of this type (including the color) during the operation of the material are of importance. Since some OSCs are used at a tempera-
ture of 500°C, heat-resistant pigments are used to preserve the color of the coating. For the green color, Cr2O3 is applied; for light green, a mixture of Cr2O3 and TiO2; for white, TiO2; etc. Pigments have no effect on heat resistance. Conversely, for example, in OSP OS-92-03, the green amount of Cr2O3 was reduced to 3 wt % and, due to the successful selection of hydrosilicates and the value С = 0.45, the coating has a heat resistance of 500°C and sa
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