盐溶液条件对边界润滑添加剂在带电表面吸附行为的影响

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

为揭示盐溶液条件对边界润滑添加剂聚醚接枝聚羧酸盐(Poly(carboxylate ether), PCE)吸附行为的影响,利用表面力仪在一种商业PCE的多种水溶液中直接测量带电云母表面之间的法向作用力。力—距离测量表明PCE从0.1 mol/L K2SO4溶液中微弱地吸附于云母表面,其边界吸附薄膜(厚度约50?)在相当于三四个大气压的载荷条件下即从两表面间完全挤出。解吸附之后,PCE能立即实现相同的再吸附。在相同离子强度的0.1 mol/L Ca(NO3)2溶液中,PCE却不吸附于云母表面。但是,在低浓度的5 mmol/L Ca(NO3)2溶液中,PCE在云母表面建立厚度约40?的牢固边界吸附层。二价Ca2+离子能桥接两PCE边界吸附层,而单价的K+离子不能。二价阳离子桥接吸附机理只能在有限的离子浓度范围内发生。

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 ? 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.