Tribological Properties And Mechanism Research Of Epicuticular Wax As Green Lubricant Additives

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,they were utilized as a new type of environmentally lubricant additive adding into base oil to investigate the tribology properties.In order to explore the feasibility of plant leaf wax as lubricant additives,four kinds of arbor plants(Sophora japonica,Photiniax fraseri,Pittosporum,and Ilex chinensis)were selected as the research object.Four types of plant cuticles were distilled from leaves and the resulting lipid mixtures were analyzed using gas chromatography-mass spectrometry.Synthetic ester was utilized as base oil and plant waxes were 'then used as additives for required lubricants.A reciprocating friction and wear testing machine was utilized to investigate the resulting tribological properties.Three types of friction pairs were adopted:steel-steel,steel-aluminum and copper-aluminum.Under steel-steel friction pair,commercial additive MoDTC was used as a control.The worn surfaces of the lower discs were observed and analyzed using metallographic microscopy and time-of-flight secondary ion mass spectrometry.In the end,the data were analyzed by means of mathematical technique,combined with the resultant on the worn surface,tribological mechanism were explored in depth,and conclusions are drawn as below:1.Extracts from Sophora japonica(SJ),Photiniax fraseri(PH),Pittosporum(PI),and Ilex chinensis(IC)contain aliphatic,aromatic and naphthenic compounds with a large amount of oxygen containing group and the largest fractions of the cuticular wax components are alkanes and alcohols.The constituents of PH wax are diversified heterocyclic compounds while the other three kinds of wax in which the highest content is aliphatic compound,such as VLC hydrocarbon and alcohol.2.Plant additives have the best performance for steel-steel frictional couple,and under this condition,the COF-reducing performance of IC is excellent,while SJ performs well for both anti-friction and anti-wear properties.All four plant additives have better tribological propertities than SE and MoDTC.For steel-aluminum pair,IC has the best tribology properties while SJ has better load-bearing capacity.For copper-aluminum couple,PI has the best tribology properties while PH has better load-bearing capacity.3?Twenty-nine alkane played a great role in the improvement of tribological properties while 1,30-thirty alkanediol had negative effects on that.Iron ions,oxygen negative ions,Hydroxyl Anion and very short carbon chain negative ions were found in the tribological films in application of TOF-SIMS,indicating that physical and chemical adsorption films were formed during the tribological process which can reduce the friction and abrasion.