The predictive service life of frost-resistant rubber based on polyurethane rubber, including a sulfur vulcanization system, an active grade of carbon black, and dioctyl adipate as a plasticizer, was evaluated. Based on the results of changes in the conditional tensile strength, relative elongation at break, temperature brittleness limit, glass transition temperature, hardness, and weight loss of the rubber depending on the time and temperature of thermostating, conditions were identified under which the predicted service life of the studied rubber in an unstressed state could exceed 25 000 h. The most important factor in this case is maintaining the level of frost resistance.
This paper contains the results of studies demonstrating irreversible physicochemical changes in the composition and structure of gas-filled polymers (using expanded polystyrene as an example) during natural aging under the influence of environmental factors. The identified characteristic structural changes are associated with the destruction of the polymer granule shells and the migration of the functional filler TiO2, which leads to a decrease in the density and an increase in amorphization of polymer thermal insulation. The more exposed surface of naturally aged samples contributes to increased contamination of the surface zone of the thermal insulation: nonpolymer particles (Cr, Cu, Ni, Pb, V, Zn, MgO, Sr, Fe2O3, etc.) were detected in the structure, which, to varying degrees, can affect the operational and fire safety characteristics of the material. The degree of contamination and its chemical nature largely depend on the duration and operating conditions of thermal insulation materials.
A new method for molding a composite material from epoxy resin is presented. The developed invention’ technical objective is to improve the strength properties of a composite material based on an epoxy resin. This objective is achieved through the use of combined electromagnetic treatment of the epoxy resin at different stages of the composite material molding process.
This article concludes a series devoted to studying the influence of milling conditions (feed rate and milling cutter speed) on changes in static and cyclic flexural strength of carbon fiber reinforced plastics (CFRP) under adverse climatic conditions (low subzero temperatures (–50°C), water dust, and salt fog). This study was conducted on individual carbon fiber reinforced plastic (CFRP) samples obtained by milling using two comparable milling conditions. Milling using higher milling conditions results in a decrease in CFRP stiffness after exposure to adverse climatic conditions. Based on the comprehensive research conducted, an algorithm for selecting milling conditions was developed and presented.
Initial stage of aging of the epoxy polymer Etal-247 in the cold climates of Tiksi and Yakutsk was studied. Deformation, strength, and dynamic mechanical properties of Etal-247 vary widely when using the hardeners Etal-1472, Etal-45TZ2, Etal-45M, and Etal-M7. After exposure for three winter months, a significant deterioration in mechanical properties was observed, caused by the sorbed moisture’ plasticizing effect. Depending on the hardener used, the glass transition temperature of polymer decreases by 8–22°C upon moisture sorption. Effect of moisture was reversible. After removal of moisture, the deformation, strength, and dynamic mechanical properties returned to their original values. As a result of climatic influence, the degree of crosslinking increases, which is caused by the additional curing of Etal-247, which is most noticeable when using the Etal-1472 hardener.
