Formulation of lyotropic liquid crystal emulsion based on natural sucrose ester and its tribological behavior as novel lubricant

作     者：Yumei GUO Jiusheng LI Xiaojie ZHOU Yuzhao TANG Xiangqiong ZENG Yumei GUO;Jiusheng LI;Xiaojie ZHOU;Yuzhao TANG;Xiangqiong ZENG

作者机构：Laboratory for Advanced Lubricating MaterialsShanghai Advanced Research InstituteChinese Academy of SciencesShanghai 201210China University of Chinese Academy of SciencesBeijing 100049China National Facility for Protein Science in ShanghaiShanghai Advanced Research InstituteChinese Academy of SciencesShanghai 201210China 

出 版 物：《Friction》 (摩擦（英文版）)

年 卷 期：2022年第10卷第11期

页      面：1879-1892页

核心收录：

学科分类：081702[工学-化学工艺] 08[工学] 0817[工学-化学工程与技术] 0802[工学-机械工程] 

基　　金：We thank the Pudong New Area Science&Technology Development Fund(Grant No.PKJ2020-N007) the BL19U2 and BL01B beamlines of the National Facility for Protein Science in Shanghai(NFPS)at Shanghai Synchrotron Radiation Facility,China,for the support in the SAXS,WAXS,and synchrotron infrared micro-spectroscopy measurements(Grant Nos.2020-NFPS-PT-004482 and h21pr0002). 

主　　题：lyotropic liquid crystal(LLC) emulsion aqueous lubrication tribological behavior 

摘      要：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.