• CN: 11-2187/TH
  • ISSN: 0577-6686

Journal of Mechanical Engineering ›› 2021, Vol. 57 ›› Issue (9): 118-126.doi: 10.3901/JME.2021.09.118

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Effect of Salt Solution Condition on Adsorption Behaviors of Boundary Lubrication Additive on Charged Surfaces

WU Bo1,2, GU Le3, CAO Huajun1,2, QU Da1,2   

  1. 1. College of Mechanical and Vehicle Engineering, Chongqing University, Chongqing 400044;
    2. State Key Laboratory of Mechanical Transmissions, Chongqing University, Chongqing 400044;
    3. School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001
  • Received:2020-07-11 Revised:2020-12-08 Online:2021-05-05 Published:2021-06-15

Abstract: To reveal the effect of salt solution condition on adsorption behaviors of boundary lubrication additive poly(carboxylate ether) (PCE), normal interaction forces are directly measured between charged mica surfaces in multiple aqueous solutions of a commercial PCE by a surface forces apparatus. Force—distance measurements indicate that the PCE weakly adsorbs onto mica from 0.1 mol/L K2SO4 and its boundary adsorption layers (about 50 Å thick) are totally squeezed out from the surface gap under an equivalent load level of three to four atmosphere pressures. The PCE is able to immediately accomplish the same adsorption after desorption. In the same ionic strength condition of 0.1 mol/L Ca(NO3)2, the PCE does not adsorb onto mica. However, the PCE builds up a 40-angstrom-thick robust adsorption layer on mica in the low calcium solution of 5 mmol/L Ca(NO3)2. Divalent Ca2+ ions are able to bridge adsorbed PCE layers while monovalent K+ ions unable. The divalent cation bridging adsorption mechanism only functions in a finite ion concentration range.

Key words: adsorption, boundary lubrication additive, poly(carboxylate ether), salt condition, surface forces apparatus

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