固液界面润湿性对面接触乳化液成膜特性的影响

乳化液广泛应用于机械加工装备，在不同润湿性界面下的摩擦润滑机制亟待明晰。通过涂镀疏油层AF(氟改性有机基团，主要成分为CF(CF₃)CF₂O]_x(CF₂O)_y)和FAS(C₁₃H₁₃F₁₇O₃Si)对轴承钢滑块进行修饰，采用光干涉法测量不同润湿性(AF、FAS、Steel)界面乳化液膜厚度。结果表明：界面润湿性不同导致乳化液膜厚发生较大变化，同卷吸速度下AF表面膜厚最高，Steel表面次之，FAS表面膜厚最低。稀释前乳化液原液成膜能力与其在入口处所受Laplace压力正相关；稀释后乳化液油水两相存在竞争吸附行为，乳化液成膜厚度受水相将油相从固体表面分离所做黏附功影响。结合光致荧光法和固水油三相黏附功共同分析界面润湿性对乳化液成膜的影响，认为涂镀AF后乳化液更易进入接触区。AF界面乳液池特性与油膜厚度的关系，证明了疏油表面可以具有较好的成膜能力。

Effect of Solid / liquid Interface Wettability on Film Formation of Emulsion in Conformal Contact

Emulsion are widely used in mechanical processing equipment. However, their friction and lubrication mechanisms at different wettability interfaces still need to be clarified. The film formation properties of emulsions on different wettability surfaces were studied using a micro-slider on a rotating disc oil-film measurement system in conformal contact. The wettability of the slider working surface was changed by applying oleophobic layers of AF (CF(CF₃) CF₂O]x (CF₂O)y) and FAS (C₁₃H₁₃F₁₇O₃Si). The emulsion film thicknesses of the AF, FAS and unmodified steel surfaces were measured by optical interferometry. The test results showed that differences in interfacial wettability led to a significant change in the thickness of the emulsion film. At the same entrainment speed, the oil film thickness at the AF interface was higher than that of the steel surface, whereas the film thickness of the FAS surface was the lowest. The emulsion film thickness of the AF surface with different concentrations tends to be constant at a high speed. Low-viscosity emulsions require a higher entrainment speed to achieve the same film thickness. A positive correlation exists between the film thickness and viscosity on both the steel and FAS surfaces. To explore the reasons for the different film thicknesses of the emulsions on different wettability surfaces, the emulsion was fluorescently treated with R6G at a concentration of 0.5 mmol / L. The pool distribution of the emulsion stock solution was determined by fluorescence microscopy. The cross-sections of the reservoir characteristics along the entrainment direction speed of the interfacial emulsions with different wettabilities were extracted. The emulsion formed a curved surface at the entrance of the contact zone. Different surface wettabilities resulted in different curvatures of the liquid surface. The radius of curvature of the liquid surface formed by the emulsion on the surface after the application of the FAS coating was the largest, followed by the steel surface, with the smallest on the AF surface. Based on the inverse relationship between the radius of curvature and Laplace pressure, the Laplace pressure at the inlet of the emulsion reservoir before dilution is positively correlated with the oil film thickness. The AF surface emulsions were subjected to high Laplace pressures, allowing easier access to the contact area. Diluted emulsified droplets will break inside or before the contact area under the combined action of the interaction forces between the droplets, shear force and sliding force. After the rupture, a competitive relationship emerges between the oil and water phases. Theoretical analysis showed that the oil phase formed an oil film in the contact area by a plate-out mechanism, which plays a major load-bearing role. The film-formation ability is affected by the adhesion work performed by the water phase to separate the oil phase from the solid surface. The surface energies of the different wettability sliders were calculated by the Owens two-liquid method. Based on the contact angles of the emulsions at the interface of the steel, AF and FAS, the three-phase solid-water-oil adhesion work was calculated. When the dispersion component of the emulsion is between 47.4 mN / m and 60 mN / m, the calculated value of the adhesion work is consistent with the variations in the film thickness. In the experiment, the fluorescence method and three-phase solid-water-oil adhesion work were combined to analyze the effects of the interfacial wettability on emulsion film formation. The film thickness of the emulsions with different concentrations significantly increased after the slider was modified by the AF. The relationship between the emulsion pool characteristics of the AF interface and film thickness proves that the oleophobic surface also has a good film formation ability.