Key Engineering Materials Vol. 899

Abstract: The article discusses the synthesis and development of the direction of vulcanization of elastomers with quinol esters of p-benzoquinone dioxime. The concept of a critical temperature T_cr which denotes noticeability of the vulcanization process of unsaturated rubbers (with k=1×10^-6, s^-1) is introduced. Noted the increased vulcanizational activity of quinol esters of p-quinone dioxime after nitrosoarenes addition. The reactional ability of nitrosoarenes is proportional to estimated charge value on the oxygen of the nitroso group, with lgk= 11,3+49,7 qO. Quinol esters of p-quinone dioxime are proposed to create three-dimensional rubber paintings and prints.

Abstract: In conclusion, one should say that, to determine the approximate stress state in the body, it is quite enough to consider the problem in a linearized problem setting. When determining the deformed state, it is necessary to consider the problem exclusively in a nonlinear setting.

Abstract: A high risk of complications in burn injuries is associated with the development of systemic inflammatory response syndrome. Thermal injury (burn) causes the release of cytokines and prostaglandia, resulting in increased interaction between leukocytes, platelets and endothelial cells. Activation of leukocytes leads to an increase in the formation of reactive oxygen species (ROS) and nitrogen, which is normally compensated by the activation of protective antioxidant enzymes. An imbalance between the activity of the radical-producing and antioxidant systems leads to an excess of free radicals and the development of oxidative stress. Oxidative stress limits the repair of damaged tissue and also leads to localized chronic inflammation. Thus, the removal of inflammation and a decrease in the ROS level, which exceeds the physiological level in the burn zone, seems to be expedient for accelerating the healing process of burn injuries of the skin. In this study, we used a polysaccharide hydrogel modified with cerium dioxide (CeO₂) nanoparticles, which have unique anti-inflammatory and antioxidant properties, as an effective agent for the treatment of thermal burns. It has been shown that modification of the hydrogel with CeO₂ nanoparticles provides accelerated healing of a model burn wound in rats. Already on the 5th day after the treatment of damage to the skin with the modified hydrogel, a decrease in the area of ​​the burn wound that is different from the control is observed. The use of a hydrogel accelerates the healing process of a burn wound on the 25th day by 25.42% (p <0.05) and ensures complete healing of burn wounds on average 5 days earlier in comparison with the control group with Levomekol ointment. Treatment of burn wounds using a hydrogel leads to the formation of a small post-burn scar. Thus, a polysaccharide hydrogel modified with CeO₂ nanoparticles can be considered as an effective wound healing agent in the treatment of thermal burns and skin lesions of various etiologies.

Abstract: Atomic force microscopy techniques (conductive-AFM, I-V spectroscopy and PFM) were used for characterisation of the local electrical properties of bilayer polyaniline-polystyrene/P(VDF-TrFE) polymer nanocomposite. Observed hysteresis of current-voltage characteristics confirms its memristive properties. It was caused by the influence of the ferroelectric polarization of P(VDF-TrFE) layer, the domain structure of which was visualised by piezoelectric force microscopy on the transport of charge carriers at the interface.

Abstract: The paper considers the dependence of the strength properties of 3D-printed parts on FDM printing modes (temperature and speed), as well as the layer arrangement. PETG (polyethylene glycol terephthalate) based filament was chosen as the basis. A 3D printer was used to produce samples with strictly defined orientation of layers — longitudinal and transverse tensile force at different temperature and printing speed. The experiment has established the effect of these two factors on the tensile strength. The strength of the samples printed transversely was higher than the strength of samples printed longitudinally. This indicates a higher interlayer adhesion.

Abstract: A synthetic method for the new chain extenders with different amounts of furan groups and a prepolymer derived from three-furyl diol was developed. A series of polyurethanes cross-linked via the Diels-Alder reaction with various amounts of bismaleimide were produced. The structure, mechanical and thermal properties, and recycling ability of the obtained materials were investigated.

Abstract: The influence of various tacticity regulators on the reversible addition-fragmentation (RAFT) polymerization of 2,2,3,3-tetrafluoropropyl methacrylate in the presence of 2-cyano-2-propyldodecyltritiocarbonate as an chain transfer agent was investigated. Among Lewis acids considered, the polymerization of TFPMA in dioxane with ZnBr₂ turned out to be the most effective from the point of view of tacticity; the polymer with the highest isotacticity is formed. The addition of hexafluoroisopropanol leads to an increase in the heterotacticity and a decrease in the isotacticity of the polymer chain.

Abstract: The paper investigates the dependence of the reduced viscosity and some properties of aromatic copolyethersulfone ketones on the chemical structure of diphenols and activated dihaloid compounds on the conditions of copolycondensation processes. It is shown that the course of copolycondensation processes and important performance characteristics of products are significantly influenced by the chemical structures of the starting monomers and the order of their introduction into the reaction.

Abstract: The paper investigates the processes of carbon fiber surface treatment and their influence on the properties of polyetheretherketone composites. It has been shown that preliminary thermal activation of carbon fiber followed by treatment with a dressing agent - polyhydroxyether makes it possible to create polyetheretherketone composite carbon-filled materials with an increased level of physical and mechanical properties.

Abstract: The presented work presents the results of the studies carried out to elucidate the possibility of obtaining by the microencapsulation method of powdered polyetheretherketones and spherical copolyetheretherketones recommended for use in 3D-printing. The influence of temperature-time and concentration parameters, the reaction medium on the size of microencapsulated particles of polyetheretherketones and copolyetheretherketones was determined. It was determined that the bulk density of microencapsulated particles of polyetheretherketone and copolyetheretherketones is 8-10 times higher than similar unencapsulated ones.