Abstract
The plant cuticle is a complex mixture of omnipresent, commonly monofunctional, fatty acid derivatives and taxon-specific, generally bifunctional, specialty compounds. This study explored expanded applications for these substances. Four types of plant cuticles were distilled from leaves and the resulting lipid mixtures were analyzed using gas chromatography-mass spectrometry. These were then used as additives for a synthetic ester lubricant. A reciprocating friction and wear testing machine was utilized to investigate the resulting tribological properties. The worn surfaces of the lower discs were observed and analyzed using optical microscopy and time-of-flight secondary ion mass spectrometry. The results reveal that cuticular waxes can modify the friction properties of the base oil. Furthermore, cuticular waxes demonstrate better performance when compared to the commercially available additive molybdenum dithiocarbamates. A protective adsorption film was identified as the reason for the improved friction reduction and anti-wear properties of the lubricant on the friction pair. This study provides a reference for the study of new types of non-sulfur, phosphorus, and other active element additives and demonstrates considerable potential for the economical utilization of plant leaf waxes.
Highlights
The overwhelming majority of terrestrial flora has a layer of wax coating that serves to protect them from injuries and the surrounding environment [1]
Wax was extracted by the following series of steps: (1) pick and collect leaves; (2) wash the leaves with water and brush carefully and gently to remove any impurities without damaging the blade surface; (3) air-dry the leaves at room temperature; (4) steep the leaves in a chloroform solution (SJ leaves are very soft and thin; they are bathed in the solution for 10 seconds, while the other leaves are bathed for 30 seconds); (5) let the solution completely volatilize in an exhaust ventilation system; (6) glean the precipitate
Epicuticular waxes have excellent friction-reducing and anti-wear properties when used as lubricant additives, compared with Synthetic ester (SE) and molybdenum dithiocarbamate (MoDTC), and clearly enhance the function of SE
Summary
The overwhelming majority of terrestrial flora has a layer of wax coating that serves to protect them from injuries and the surrounding environment [1] This cuticle is the outermost hydrophobic layer that is non-cellular, and consists of cutin and waxes covering the external surfaces of plant leaves, flower petals, and non-woody stem organs. According to the results of prior research, the dominant constituents in most plants are very-long-chain saturated aliphatic compounds that may or may not have additional functional groups. The chemical compounds in the cuticular wax are mixtures of homologous series, with chain lengths typically ranging from 24 to 34. In the plant waxes of some species, the content of alicyclic compounds such as triterpenoids can be highly dominant, and in some cases, it exceeds the amount of very-long chain (VLC) aliphatics present.
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