Application of Microcapsules with Lubricants in Tribotechnics

Reducing of Friction in The Units of Transport Systems, Due to The Formation of Boundary Lubricating Films

M. Boiko, I. Kolesnikov, T. Boiko

Rostov State Transport University, Rostov-on-Don, Russia
РОСЖЕЛДОР
Федеральное государственное бюджетное образовательное учреждение
высшего образования
«Ростовский государственный университет путей сообщения»
(ФГБОУ ВО РГУПС)
Reducing friction losses in machine and mechanism assemblies is an important scientific and technical task that is solved at all stages of the tribo-units life cycle, starting with the design, selection of operating conditions and materials corresponding to these conditions, providing technological aspects of manufacturing and completing with the selection of lubricants. The correct selection of the component composition and the lubrication conditions of the units can significantly reduce the fuel and energy costs for the operation of transport systems.
The aim of this work was to establish specific chemical reactions that lead to the formation of boundary films in ester lubricants. For this purpose, we have considered the most probable transformations of organic substances in which metallic iron and iron oxides exhibit catalytic activity.
Structural formulas of ester oils
bis(2-ethylhexyl)sebacate (DEHS)
sunflower oil
pentaerythritol esters
Tribograms of 1 – DEHS, 2 – sunflower oil, 3 – pentaerythritol esters
Tribological tests
(a)
(b)
(c)
Destruction of esters molecules: (a) – DEHS, (b) – sunflower oil, (c) – pentaerythritol esters
(a)
(b)
Transformations of fragments of DOS molecules in interaction with iron:
(a) – formation of unsaturated compounds,
(b) – growth of tribofilm
(a)
(b)
Transformations of fragments of sunflower oil molecules in interaction with iron:
(a) – transformation of a primary radical into a secondary radical,
(b) – formation of unsaturated compounds
(a)
(b)
(c)
Transformations of pentaerythritol ester molecules: (a) – formation of three-membered cycle, (b) – decarboxylation of ester group, (a) – formation of radical particles
Conclusion
The analysis of a chemical transformations set in which metallic iron and iron oxides are the catalyst showed that during the formation of boundary lubricating films, reactions of lubricant molecules destruction with the participation of non-oxidized iron occur.
When interacting with metallic iron, the molecules of esters are decarboxylated and free radicals are formed, they are fixed on the metal surface. As a result of the dehydrogenation of such particles, unsaturated compounds are formed, the polymerization of which leads to the formation of boundary lubricating layers.
Tribo-chemical transformations of sunflower oil and pentaerythritol esters are determined by the structural features of free radicals formed during decarboxylation.
Acknowledgements
The research was carried out at the expense of the Russian Science Foundation grant No. 18-19-00292, https://rscf.ru/project/18-19-00292