Abstract
The tribological behavior of oil-in-water emulsions formulated with natural lyotropic liquid crystal (LLC) emulsifiers based on natural sucrose ester was studied for the first time. Polarized optical microscopy, synchrotron radiation small-angle X-ray scattering, wide-angle X-ray scattering, and synchrotron radiation infrared microspectroscopy demonstrated that LLC emulsifiers were tightly ordered at the oil—water interface with a distinct nematic texture. The viscosity of emulsion was observed to change over time. Moreover, the zeta potential and laser particle size distribution verified the emulsion’s satisfactory stability. The frictional shearing test proved that the coefficient of friction of the emulsion versus pure oil decreased by 34.2%. The coefficient of friction of the emulsion with liquid crystal decreased 10.1% versus that without liquid crystal. Although liquid crystal emulsion did not exhibit outstanding anti-wear performance compared with pure oil, its wear volume was 29.4% less than the emulsion without liquid crystal. X-ray photoelectron spectroscopy and scanning electron microscope—energy dispersive X-ray spectroscopy (SEM—EDS) proved that the tribo-film of the emulsion with liquid crystal was formed synergistically by the liquid crystal phase with the base oil. The formulation affecting the lubricant quality was further studied by orthogonal experiments. The resulting Stribeck curve behavior suggested that proper composition with a slightly higher viscosity can better reduce friction in both boundary lubrication and mixed lubrication regimes. The lubrication mechanism indicated that the periodically ordered liquid crystal was transported to the sliding asperity in the form of emulsion droplets, which bored the pressure and released the oil to form a tribo-film. This LLC emulsion is environmentally friendly and potentially non-irritant to the skin. Thus, it has promising application prospects as novel water-based and biological lubricants.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
