Physicochemical regularities of processes occurring in the "polyorganosiloxane-silicate-metal oxide" system are investigated over a wide range of temperatures. The results of investigations are used to design organosilicate materials, such as heat-resistant functional coatings, high-temperature adhesives, and vacuum-tight sealants, which find wide application in various fields of engineering. Modern materials science of organosilicate composites is a dynamic knowledge system.

The influence of the parameters of curing of organosilicate coatings and the degree of completeness of interfacial chemical reactions on the total surface energy, its dispersion and polar components, and the physicochemical and protective properties of coatings is analyzed. The possibility of using organosilicate coatings as easily cleanable materials is determined by the small values of the surface energy and its polar component.

The factors characterizing the adhesion of water to the coating surface are analyzed. The compatibility of polymer components and its influence on the characteristics determining the anti-icing properties of coatings are considered. It is demonstrated that the use of the complementing results obtained by physicochemical methods of investigations and operational, accelerated, and natural tests makes it possible to properly choose and optimize the coating compositions.

The functional role of sepiolite in organosilicate composites is investigated. It is demonstrated that the addition of the organomodified sepiolite to organosilicate composites during their fabrication in amounts of 1 wt % increases the thixotropy and pseudoplasticity of "polydimethylphenylsiloxane-silicate-inorganic pigment" suspensions and prevents sedimentation of pigments and fillers, as well as the formation of dense sediments in the course of storage. Upon introduction of this stabilizing additive, the physicomechanical and protective properties of organosilicate coatings remain good.

INTRODUCTIONOrganosilicate coatings are represented by films with specific functional properties [1][2][3]. Commercial organosilicon oligomers have been used as film formers. In the case of high-temperature composites, the functional properties are provided by the use of mineral components (finely dispersed layered silicates), inorganic pigments, and special modifiers (for example, vitreous additives, finely dispersed metal powders, etc.).The curing of organosilicate composites (OSCs) and coatings in the course of heat treatment, as a rule, is associated with the condensation of silanol groups of polyorganosiloxanes and the removal of water thus formed from the coating. An increase in the temperature accelerates these processes and makes it possible to achieve a more complete curing (this manifests itself in a decrease in the content of the soluble fraction in the coating). The kinetics of curing and aging of organosilicate composites is affected by oxidants of the environment (for example, oxygen) and the oxidizing and reducing agents introduced into the composition of organosilicate composites.The purpose of this work was to investigate the role of chemical reactions in the formation and aging of heat-resistant organosilicate composites and coatings. SAMPLE PREPARATION AND EXPERIMENTAL TECHNIQUEFive model organosilicate composites ( I -V ) in the "polydimethylphenylsiloxane (PDMPS)-mica-asbestos-zirconia" system were prepared for investigation. The composites differed in the presence or absence of a vitreous additive, vanadium oxide V 2 O 5 , and barium peroxide. The organosilicate composites were prepared through mechanochemical treatment of different components in a ball mill (Table 1).Composite I contains the polymer, mica, asbestos, glass, and zirconia and does not involve the vanadium oxide and barium peroxide. The glass is absent in composite II . The vanadium oxide is absent in composites III and IV ; in this case, the latter composite does not involve the glass. All the above components are contained in composite V .In this work, we used the organosilicon varnish, which was a 65-67% solution of polydimethylphenylsiloxane of the composition {[C 6 H 5 SiO 1.5 ][[CH 3 SiO 1.5 ] 0.42 [(CH 3 ) 2 SiO] 1.33 ]} n modified by an organic polyester in toluene. The polyester (the product of polycondensation of ethylene glycol with phthalic and maleic anhydrides) modified by the castor oil was introduced into the polydimethylphenylsiloxane at the final synthesis stage in the ratio polymer : polyester = 10 : 1.Muscovite mica [ GOST (State Standard) 855], chrysotile asbestos [ GOST (State Standard) 12 871], zirconia, vanadium oxide V 2 O 5 , and barium peroxide (reagent grade) were used as fillers. The aluminoborosilicate glass of the composition (wt %) 53.6SiO 2 · 9.6B 2 O 3 · 14.7Al 2 O 3 · 20.9CaO · 0.7MgO · 0.5Na 2 O (according to the chemical analysis) served as a vitreous additive.The content of nonvolatile compounds in organosilicate composites I -V was determined from the weight losses of weighed portions of t...