Many grease-lubricated machinery components operate in wet environments, making them susceptible to water contamination. It has been reported that the presence of a mere 1% water contamination in grease reduces the life of a bearing by 90%. Yet there are only a few standards available to characterize grease performance in the presence of water, most of which are primarily qualitative, providing inconclusive information, often relative to standard samples, at a significant cost in time and materials. In this paper, a unique approach is proposed for evaluating grease capability for repelling water. The method utilizes the contact angle of a water droplet on a grease surface to quantify grease water resistance. It is hypothesized that the higher the hydrophobic nature of the grease, the greater the resistance to water and vice versa. The validation of the hypothesis is established by performing extensive contact angle measurements on seven types of commercially available greases. The efficacy of contact angle results is established by measuring the change in the yield stress values obtained using a rheometer. From the obtained results, it is shown that the proposed approach is reliable and capable of distinguishing greases as water repellent/attractive.

Graphic Abstract

中文翻译：

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接触角法评估油脂中的水污染

许多油脂润滑的机械组件都在潮湿的环境中运行，因此容易受到水的污染。据报道，润滑脂中只有1％的水污染会降低轴承寿命90％。然而，只有少量标准可用来描述在水存在下的润滑脂性能，其中大多数主要是定性的，通常相对于标准样品而言，它提供了不确定的信息，而这会花费大量时间和材料。在本文中，提出了一种独特的方法来评估油脂的拒水能力。该方法利用水滴在润滑脂表面上的接触角来量化润滑脂的耐水性。据推测，润滑脂的疏水性越高，其对水的抵抗力越大，反之亦然。通过对七种市售润滑脂进行广泛的接触角测量，可以建立该假设的验证。通过测量使用流变仪获得的屈服应力值的变化来确定接触角结果的功效。从获得的结果可以看出，所提出的方法是可靠的，并且能够将油脂区分为疏水性/吸引力的。

图形摘要