Formation of effective concentration of film forming superhydrophobic coatings based on silicon dioxide

The object of research is the hydrophobization of a coating based on styrene-acrylic copolymer and cellulose acetate butyrate with pyrogenic silicon dioxide. The hydrophobicity or hydrophilicity of a surface depends mainly on the chemical structure of the surface and its roughness. A relief hydrophilic surface will be wetted much more easily than a flat surface of the same material, and vice versa – an increase in the roughness of a hydrophobe is accompanied by a more pronounced repulsion of water. The size and number of irregularities significantly affect the wetting characteristics of the investigated surface. The combination of low surface energy and relief structure forms a superhydrophobic surface. Such surfaces have found application in self-cleaning, frost-resistant, antifriction, electrically conductive and oil-sorbing coatings. In this work, styrene-acrylic copolymer and cellulose acetate butyrate were used as a film former. Pyrogenic silicon dioxide Aerosil R 972, which was hydrophobized with dimethyldichlorosilane, was used as a nanofiller. In this work, the compositions were applied to laboratory glasses by dip coating. The determination of surface energy was carried out using glycerin and diiodomethane. The hydrophobic properties of the coatings were evaluated by measuring the contact angles with water using a goniometer. The analysis of the morphological structure of the coating surface with photographs of a scanning electron microscope has been carried out. The energy state of the surface of the created superhydrophobic coatings has been determined and their surface energies have been calculated using the technique based on the Owens-Wendt model. The process of hydrophobization of polymer-based coatings is investigated, which occurs both due to chemical modification with the introduction of silicon dioxide and due to the creation of nanoroughness of the surface layer of the coatings. The dependences of this process on materials are investigated using an electron microscope and the determination of their surface energy depending on the SiO2 filling. The values of the critical concentration of the modifier for the transition of polymers to the superhydrophobic state have been determined. As a result, the influence of polymer crystallinity on hydrophobization was determined by comparing changes in the surface energy of materials during their modification.

GENERATION OF NANO-FILLED EPOXY-POLYESTER COMPOSITE MATERIALS FOR PROTECTION OF ELEMENTS OF VESSEL TECHNICAL MEANS

The influence of nanofillers on thermophysical properties of epoxy-polyester composites has been investigated in the work. The filler content (oxidized nanodisperse additive and pyrogenic silicon dioxide) has been varied within q = 0.02…1.0 pts.wt. per 100 pts.wt. of epoxy oligomer ED-20. It has been discovered that the introduction of the oxidized nanodisperse additive in the amount of q = 0.05…0.08 pts.wt. into the epoxy-polyester binder leads to an improvement in the thermophysical properties of the composite. Value of heat resistance (according to Martens) increased from Т = 335 К (for the epoxy-polyester matrix) to T = 346 K at the content of oxidized nanodisperse additive of q = 0.075 pts.wt. Introduction of q = 0.05 pts.wt. of oxidized nanodisperse additive allows to obtain improved values of the temperature coefficient of linear expansion in different temperature ranges: in the region ΔT = 303…323 K – α = 1.0 × 10-5 K-1, in the region ΔT = 303… 373 K - α = 1.9 × 10-5 K-1, in the region ΔT = 303… 423 K – α = 3.4 × 10-5 K-1. It has been determined that the composite material has also improved its heat resistance (according to Martens), which is T = 347 K and the minimum thermal coefficient of linear expansion at the content of q = 0.05 pts.wt. of pyrogenic silicon dioxide nanofiller. Values of the temperature coefficient of linear expansion were: α = 1.0 × 10-5 K-1 in the region (ΔT = 303… 323 K), α = 1.9 × 10-5 K-1 (in the region ΔT = 303… 373 K), Δα = 3.4 ×× 10-5 K-1 (in the region ΔT = 303… 423 K), α = 8.4 × 10-5 K-1 (in the region ΔT = 303… 473 K). It is recommended that in order to form a composite material with improved thermophysical properties to protect the elements of ship technical equipment, it is advisable to introduce the pyrogenic silicon dioxide nanofiller in the amount of q = 0.05 pts.wt. into the epoxy-polyester binder.

Silver nanoparticles deposited on pyrogenic silica solids: Preparation and textural properties

Silver-based nanomaterials and composites are important components in materials science and engineering due to the reactivity of silver nanophase based on exceptional surface effects. Ag-doped SiO2 nanocomposites were synthesized by wet impregnation procedure of aminopropyl-functionalized silica materials with submicrometer structure. Aminopropyl-functionalized pyrogenic silicon dioxide with amount of amino groups established as half and close to full monolayer was used to immobilize the nanosilver phase obtained from ammoniacal silver complex as a noble metal precursor. Pyrogenic silicon dioxide as an inexpensive nanostructured material with useful properties including adsorptive affinity for noble metal ions and organic macromolecules was applied as a support for diamminesilver(I) ions and finally for silver nanoparticles. In the present study, the effect of amino-functionalization and silver nanoparticles deposition was monitored by investigation of the textural properties and thermal stability of obtained nanocomposites. The properties of the nanocomposites were investigated by transmission electron microscopy, nitrogen adsorption–desorption isotherms, and thermal analysis (thermogravimetry/differential scanning calorimetry).