Abstract
The demand for bio-degradable lubricants is continuously increasing due to environmental concerns. One of the methods to achieve the bio-degradability property of lubricants is by using nanoparticles from bio-resources as additives in bio-degradable oils. Among the nanomaterials are nanofibers, cellulose, and graphene nanoplatelets. They can be mixed in Polyolester (POE) oil to produce lubricants for tribological applications. In a previous study, it has been confirmed that friction and wear of the tribo-pair reduced from 5 to 10% by mixing various volume percentages of bacterial cellulose (BC) into PEO as the base lubricant. The tribological performance BC containing POE base lubricant can further be enhanced by incorporating graphene nanoplatelets. This study shows that the specific wear rate of the material decreased by 20% by adding graphene nanoplatelets in BC containing POE oil. The friction and wear improvement can be related to the formation of tribofilm on the contact interface. EDS analysis indicates that oxygen played an important role in the friction and wear performance of the POE oil-based lubricant with BC and graphene additives. The tribofilm shows significant traces of oxygen elements. The presence of graphene nanoplatelets in POE oil removed the oxygen-rich layer but could not reduce the wear rate. However, incorporating both graphene and BC in POE oil significantly improved friction and wear, although the oxygen element was still traceable on the contact interface.
Highlights
Technological advancement in the lubrication industry has been directed to minimize the friction loss of the components and to develop lubricants that are bio-compatible and biodegradable
Additives with various functions can be designed and applied to improve the stability, viscosity, thermal conductivity, as well as ability to produce a protective layer on the sliding surface to reduce friction and wear
Lubricant sample L2 contains graphene dispersed in POE oil, lubricant L3 contains bacterial cellulose (BC) particles, Span 60 dispersed in POE oil, and lubricant sample L4 contains graphene, BC particles, and span 60 dispersed in POE oil
Summary
Technological advancement in the lubrication industry has been directed to minimize the friction loss of the components and to develop lubricants that are bio-compatible and biodegradable. The performance of cellulose nanocrystals (CNCs) as lubricant additives has been investigated by using mineral lubricants such as SAE40 oil (Awang et al, 2019a) or bio-degradable oils such as polyalphaolefin (PAO) base oil (Awang et al, 2019b; Li et al, 2019) It can be used as a viscosity modifier in biodegradable greases (Quinchia et al, 2014). A hybrid bacterial cellulose and graphene nanoplatelets nanoparticles could improve the heat transfer performance of the fluid and the tribological properties of the tribo system. Since both materials are bio-degradable, they could enhance the tribological performance of the bio-lubricant. The enhancement of the tribological properties of the lubricants due to the additive’s incorporation is elucidated
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