Polyamide self-lubricating composites filled with thermolysis products of lignin: composition, structure, properties

Compositions of antifriction composites with a polyamide matrix filled with carbon additives obtained by modifying hydrolytic lignin (graphite from lignin, graphite bisulfate from lignin, thermally expanded graphite from lignin) have been developed. Powders of carbon materials were impregnated with cylinder oil before being added to the polyamide matrix. The tribotechnical characteristics of filled polyamide composites, their microstructure and water absorption kinetics have been investigated. It was found that the lowest values of the friction factor are observed in composites filled with thermally expanded graphite from lignin. The friction factor for such composites is 1.5-2 times less than the indicators obtained for currently used graphites. Thus, at specific loads of 0.67 and 2.33 MPa, the friction factor was 0.065 and 0.064, respectively. The investigated antifriction composites have low water absorption compared to pure polyamide. The maximum water absorption (2.2%) in the series of the studied composites had the samples filled with graphite from lignin with an oil content of 9%. According to the data of microstructural analysis, the structure of composites with additives of carbon materials from lignin is homogeneous. The components, including the oil plasticizer, are evenly distributed, the bulk of the oil is localized in the interlayer spaces. The elemental composition of the composites indicates the high chemical purity of the composites. Antifriction composites with the proposed additives are recommended for use in friction units operating in an aqueous mediumor an environment with high humidity.

REPAIR OF POWER HYDRAULIC CYLINDERS USING NEW POLYMER COMPOSITE MATERIALS

The development and implementation of a new repair technology based on the use of polymer parts made of high-performance antifriction composites in tribo-couplings of power hydraulic cylinders will reduce the cost and repair time, significantly increase the reliability of the entire hydraulic system. (Research purpose) The research purpose is in increasing the efficiency of repairing of power hydraulic cylinders of agricultural machinery by restoring tribo-conjugations with new antifriction composites based on modified caprolon. (Materials and methods) The article presents the study of the physical and mechanical characteristics of samples of polymer composites according to well- known and original methods. Authors used computer programs and original methods of equipment suppliers in the study of compounding processes, rheological and tribotechnical tests. Theoretical research using the provisions of theoretical mechanics, elasticity theory and thermophysics has been conducted. A numerical study of the introduction of a spherical indenter into a sample of a viscoelastic composite material was carried out using the ANSYS software package, the MAPDL module. (Results and discussion) The article analyzes the obtained data on the elastic-strength, rheological and tribotechnical characteristics of the studied compositions of polyamide composites. The three-component composite containing 2 percent shungite, 0.5 percent graphite, 6 surfactants has the best complex of these properties. It has been proposed to restore the operability of the piston assembly and the front cover during the repair of the power hydraulic cylinder to change their design with the installation of guide support rings made of polyamide composite into the cover and piston of the hydraulic cylinders. This will lead to a significant reduction in the wear rate of the tribo-coupling parts and reduce the complexity of repairing hydraulic cylinders. (Conclusions) Restoration of tribo-couplings of power hydraulic cylinders with the installation of a guide ring made of a new polymer composite ensures a decrease in the maximum contact stresses, the rate of their increase with an increase in the gap and, as a result, a decrease in the wear rate of the contacted parts.

Structure and Properties of New Antifriction Composites Based on Tool Steel Grinding Waste

This article investigates the impact of manufacturing technology on the structure, mechanical, and tribological properties of new antifriction composite materials based on R6M5 high-speed tool steel grinding waste. The characteristics of the new composite’s structure formation and its impact on properties after use of the established technological modes, including grinding waste regeneration, were illustrated. It was demonstrated that such technology is capable of ensuring microheterogeneous structure. The material’s structure consists of the metal matrix based on R6M5 high-speed tool steel waste and uniformly distributed CaF2 solid lubricant in the steel matrix. As compared to known iron-based composites, this structure promotes a high degree of mechanical and tribological properties. During tribological tests, anti-seize thin films of 15–20 μm are formed on the contacting surfaces. These constantly renewable films contribute to the high antifriction properties of the composite under the studied friction conditions and provide a self-lubricating effect. Such films fully cover both the material’s surface and the counterface. The formation of antifriction films results in the self-lubrication mode. The findings of the study open up the possibility of predicting the friction behavior of a composite at high temperatures by selecting the initial metal grinding waste to ensure the appropriate level of properties. The extensive use of various alloy steel-based industrial grinding waste in the re-production cycle would significantly contribute to resolving the global environmental problem of protecting the environment from pollution.