Temperature Dependence of Viscoelasticity of Lubricating Oil with Adsorptive Polymer Additives Sheared in Nanogaps

IF 2.9 3区工程技术 Q2 ENGINEERING, CHEMICAL

Tribology Letters Pub Date : 2024-06-29 DOI:10.1007/s11249-024-01884-y

Takumi Nozue, Shintaro Itoh, Naoya Okubo, Kenji Fukuzawa, Hedong Zhang, Naoki Azuma

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Abstract

Adsorptive polymer additives have been reported to improve the retention capacity of oil films under hydrodynamic lubrication and to reduce friction under boundary lubrication. These effects are believed to result from the formation of a polymer adsorption film on the surface that acts as a lubricious coating. Polymer adsorption films have become dominant in nanometer-order microscopic gaps. However, their mechanical properties are difficult to quantify. This hinders the development of polymer additives. In our previous study, we successfully measured the shear viscoelasticity of lubricants (base oils) sheared in nanogaps using an originally developed measurement method called the fiber wobbling method (FWM). In this study, we measured the shear viscoelasticity of polymer-added lubricants in nanogaps by using FWM. In addition, we developed a heating stage in the FWM to quantify the temperature dependence of shear viscoelasticity in nanogaps. As a result, the viscosity index improved and elasticity was observed in the nanogap, where the polymer adsorption film was dominant. Furthermore, our results indicated that the elasticity of the adsorbed polymer film originated from entropic elasticity.

Graphical Abstract

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含吸附性聚合物添加剂的润滑油粘弹性在纳米间隙中剪切的温度依赖性

据报道，吸附性聚合物添加剂可提高流体动力润滑条件下油膜的保持能力，并减少边界润滑条件下的摩擦。这些效果被认为是由于在表面形成了一层作为润滑涂层的聚合物吸附膜。聚合物吸附膜已在纳米级微观间隙中占据主导地位。然而，它们的机械性能很难量化。这阻碍了聚合物添加剂的开发。在之前的研究中，我们使用一种最初开发的测量方法--纤维摆动法（FWM），成功测量了在纳米间隙中剪切的润滑油（基础油）的剪切粘弹性。在本研究中，我们使用 FWM 测量了纳米间隙中添加聚合物的润滑油的剪切粘弹性。此外，我们还在 FWM 中开发了一个加热阶段，以量化纳米间隙中剪切粘弹性的温度依赖性。结果表明，在聚合物吸附膜占主导地位的纳米间隙中，粘度指数得到了改善，并观察到了弹性。此外，我们的研究结果表明，吸附聚合物薄膜的弹性源于熵弹性。

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来源期刊

Tribology Letters 工程技术-工程：化工

CiteScore

5.30

自引率

9.40%

发文量

116

审稿时长

2.5 months

期刊介绍： Tribology Letters is devoted to the development of the science of tribology and its applications, particularly focusing on publishing high-quality papers at the forefront of tribological science and that address the fundamentals of friction, lubrication, wear, or adhesion. The journal facilitates communication and exchange of seminal ideas among thousands of practitioners who are engaged worldwide in the pursuit of tribology-based science and technology.