The dynamic development and enhancement of the efficiency and safety of power engineering in the Arctic and remote Siberian regions of Russia are promising and relevant. The aim of this work is search for scientifically based approaches and methods against icing, which is one of the main problems hindering efficient use of wind turbines for autonomous power supply to remote settlements in the Far North. The necessity in the research and its relevance are confirmed by the growing interest in the development of the Arctic region by the leading world countries. The presented research strives for an optimal strategy against icing of wind turbine blades in climatic conditions typical of the Arctic coast of Russia. The efficiency of combined anti-icing methods relying on the use of aerodynamically transparent substrates, hierarchical superhydrophobic (HSH) coatings, and materials based on polytetrafluoroethylene fiber for wind turbine blades in Arctic climatic conditions was experimentally studied. It is a fundamentally new approach, which has no world analogues. For verification of the efficiency of the de-icing systems and identification of the most efficient protection methods or combination of them, an experimental comparison was made for the efficiency of superhydrophobic coatings when used separately and together with various traditional de-icing methods based on heaters and ultrasonic and vibration devices. It has been shown that the integral use of the proposed methods and approaches successfully solves the problem of developing a general anti-icing strategy.

The change in the main power parameters of poly(methyl methacrylate) ablation by continuous-wave CO2 laser radiation has been studied. Measurements of the complex parameter “target weight + recoil force of ablation flow” were carried out using a force meter with computer data recording having a time resolution of 126.5 ms. Experimental data for the initial interval of 0–2 s were approximated by a model function, the processing of which made it possible to identify changes in the target weight and the recoil force of the ablation flow during irradiation. For the moment the ablation rate reaches a stationary regime, the energy efficiency of the process in a low-thrust jet engine was determined to be Cm = 115 μN/W, which decreases over time of laser irradiation due to the formation of a crater with a concave surface and an increase in gas pressure in the ablation chamber. It is noted that the type of ablation curve and, accordingly, an approximating function for the initial stage of ablation are individual for each polymer and laser beam parameters.

The surface of chemically modified polytetrafluoroethylene, obtained by introducing 1 mol % perfluoropropyl vinyl ether in the polytetrafluoroethylene macromolecule chain, has been studied using Raman spectroscopy. Three conventional zones with varying degrees of modification are distinguishable on the surface, and the spectrum of the ablation crater is fundamentally different from that of the pristine polymer. The crater spectrum, showing a general rise in the baseline, exhibits new bands due to both double carbon bonds and absorption bands of CF3 groups. A key factor in the laser ablation process is the influence of defects in the regular structure of polymer macromolecules, both intrinsically present in the polymer and induced by laser irradiation.

The formation of laser thrust by the pressure of gases released from the crater of laser ablation of polytetrafluoroethylene in vacuum has been studied, and a model for calculating the mechanical recoil impulse of ablation products has been implemented on the basis of a gravimetric curve obtained using an electronic balance that allows direct recording during intermittent (at 5-s intervals) or continuous irradiation for 5, 10, 15, 25, and 30 s with an infrared CO2 laser. Regardless of the laser operation mode, the observed polymer weight loss by ablation is linearly related to the laser irradiation time, having a rate of 80 μN/s. The maximum mechanical recoil impulse, which appears on the gravimetric ablation curves 4.5 ± 0.3 s after the laser is switched on, is 145 ± 7 or 90 ± 20 μN s in the continuous or the intermittent irradiation mode, respectively. In this case, an increase in the time of laser irradiation of the polymer in both modes leads to an insignificant change in the specific mechanical recoil impulse within 2.76 ± 0.06 μN/J. The results of the study show the possibility of using a polytetrafluoroethylene target for laser thrust, and the method of calculating the force momentum from the gravimetric curve of ablation of polytetrafluoroethylene can be used to investigate the mechanism of laser ablation of other polymer targets.

The XPS method was used to study the composition of the surface of carbon fibers after modification in a low-temperature plasma in an octafluorocyclobutane medium. It has been shown that ionic and semi-ionic fluorine bonds are formed on the surface of carbon fibers at the initial stages of treatment (30–60 s), and, then, a coating is formed that is similar in composition to polytetrafluoroethylene, but is characterized by a branched structure and the content of oxygen groups. The influence of the initial state of the surface of carbon fibers, namely, preliminary oxidation, on the composition of the formed fluoropolymer coating has been studied.

This paper reports on studies of tribotechnical behavior under conditions of friction without lubrication and the mechanical properties of fluoroplastic composites with discrete carbon fibers obtained from different grades of fluoroplastic-4 (F-4, PTFE). The particle size of PTFE powder and its mechanical properties influence the tribotechnical properties of composites with carbon fibers. The wear resistance and PV factor are higher and the friction coefficient is lower for the composite based on F-4 grade PN 90, whose powder particles are larger than the PTFE particles of the other studied grades. Composite made of modified fine-particle PTFE (grade TFM 1705) showed the highest modulus of elasticity and strength. It is assumed that large PTFE particles, which affect the mechanical properties of the composite negatively, contribute to a more intense formation of a transfer film during friction, and also reduce the contact area, which reduces the friction coefficient with increasing pressure in the friction zone.

ВЛИЯНИЕ СОДЕРЖАНИЯ МОДИФИЦИРОВАННЫХ УГЛЕРОДНЫХ ВОЛОКОН НА ФИЗИКО-МЕХАНИЧЕСКИЕ СВОЙСТВА МАЛОНАПОЛНЕННОГО ПТФЭ

One of the important tasks of the technology of surface treatment by plasma techniques is modification of sophisticatedly shaped items containing surface areas that are not directly accessible to the modifier. Gaseous organofluorine compounds are known to be used for plasma treatment of fibrous carbon fillers to improve the adhesive interaction with a binder [1]. However, the mechanism and results of the action of plasma of f luorinated gases on the surface of fibrous carbon materials, which are porous electrically conductive systems, have not been studied to a sufficient extent. One of the urgent problems is to increase the efficiency of processing the inner surfaces of fibrous– porous materials. The theoretical foundations of the treatment of hard-to-reach surfaces in relation to the synthesis of thin-layer coatings on them from the gas phase were initially developed in [2–5]. Theoretical conclusions were confirmed in experiments with the synthesis of poly-p-xylylene [2, 3, 6–9]. The aim of this work is to elucidate the main features of the formation of polymer coatings on hard-toreach surfaces for gaseous media in a narrow cavity during deposition from a glow discharge in an octafluorocyclobutane (C4F8 cycle, OFCB) medium. Experiments on the study of the effect of OFCB plasma on half-open surfaces, including the plasma with small admixtures of atmospheric gases, were carried out in a cylindrical chamber with parallel plate electrodes. The inhomogeneity of the thickness of the coating synthesized from the products of plasma-chemical transformations of OFCB on the surfaces of sensors placed in a narrow cavity in the absence of direct exposure to plasma was studied. Plasma-activated products could enter the cavity only from one side. The dimensions of the cavity formed by two polished plates fixed in parallel with a gap of 3 mm were 125 × 84 mm. One of the lateral sides of the cavity is open to the outside, and the other three are muffled and sealed to prevent uncontrolled penetration of plasma components. Quartz resonators with an open disk crystal of 8 mm in diameter were placed inside the cavity, serving as sensors for coating deposition or etching. The sensors were placed in two rows along both sides (side walls of the cavity): near the open side, in the middle of the gap, and near the plugged end at distances of 12, 56, and 106 mm from the open side of the gap. The layout of the cavity with installed sensors is shown in Fig. 1.

The irradiation of a poly(vinylidene fluoride) (PVDF) plate with γ-rays up to 100 kGy leads to the breaking of the chain and the formation of unsaturated bonds but practically does not have any effect on the conformation composition of PVDF macromolecules. The main conformer, as in native PVDF, is the β form. Irradiation with an IR laser leads to a noticeable carbonization of PVDF macromolecules and is accompanied by a structural transition of polymer macromolecules from the β conformer to the α conformer. In the IR spectrum of the powdered product from laser ablation of PVDF, in addition to the absorption bands of the ablation crater, absorption bands from the parent PVDF are still present.

Irradiation of polyamide-6 (PA) with γ-rays reduces its resistance to subsequent IR laser radiation. The average rate of laser ablation of PA, preliminarily irradiated with γ-rays at a dose above ~300 kGy, is almost dose-invariant and is 30% higher than that of the initial unirradiated polymer. The pattern of the dose dependence of the laser ablation rate for the samples pre-irradiated with a dose of 3.24 MGy at a dose rate of 4.2 Gy/s is mixed in character, varying from the shape characteristic of the initial polymer at the initial stage to the shape typical of the maximum radiation dose in the stationary laser ablation mode. One of the products of PA laser ablation is a dispersed polymer, consisting of nano- to micrometer-sized particles, the size range of these particles shifting toward smaller values with an increase in the γ radiation dose, a trend that is explained by a decrease in melt viscosity.

The effect of preliminary γ-irradiation on accelerating the speed of laser ablation of a polyamide is measured for the first time. A linear increase of intensity with a rate of 0.15 mg/s is observed during laser ablation of the polyamide pre-irradiated with γ-rays at a dose of 3,500 kGy. A γ-radiolysis dose of 10 – 20 kGy causes extreme changes in the molecular-topological parameters and the maximum level of growth of the rate of laser ablation. Thus pre-irradiation with γ-rays may be used to optimize the laser ablation of the polymer.