Characterization of Branched-Chain Fatty Acids as Organic Friction-Modifier Additives for Boundary Lubrication

IF 3.3 3区工程技术 Q2 ENGINEERING, CHEMICAL

Tribology Letters Pub Date : 2025-10-18 DOI:10.1007/s11249-025-02067-z

Masanori Iizuka, Masashi Mizukami, Kazue Kurihara

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Abstract

Organic friction modifier additives, such as fatty acids, are widely used in the boundary lubrication regime to reduce friction. In this study, we employed resonance shear measurements to study 0.1 wt% solutions of branched-chain fatty acids in a linear model base oil/hexadecane and branched base oil/poly(α-olefin) (PAO) confined between mica surfaces under various applied loads (L). At L = 3.3 mN, the viscosity parameter (b_s) values of isostearic acid and isostearic acid T in hexadecane were one-seventh and one-thirtieth of the value of pure hexadecane, respectively. Especially, isostearic acid T in hexadecane had a lower viscosity parameter b_s value, one-eighth that of pure hexadecane even at L = 22.7 mN. On the other hand, the b_s value at L = 3.3 mN of isostearic acid in PAO was half the value of pure PAO and this effect disappeared at L = 11.6 mN; isostearic acid T in PAO resulted in a behavior similar to that of pure PAO. The densely packed structure of linear lubricants as hexadecane confined between the surfaces is known to cause a high b_s value and such a structure could be disturbed in the presence of branched-chain fatty acid additives. In case of the branched base oil, such as PAO, the densely packed state was not formed under confinement, thus the effect of the branched-chain fatty acid additive was not significant. This study demonstrated that a relatively small difference in molecular structure of an additive is important for efficiently reducing friction, especially in the boundary lubrication regime of linear base oils.

Graphical Abstract

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支链脂肪酸作为边界润滑有机摩擦改性添加剂的表征

有机摩擦改性剂添加剂，如脂肪酸，广泛用于边界润滑制度，以减少摩擦。在这项研究中，我们采用了共振剪切测量，研究了0.1 wt%的支链脂肪酸溶液中基础油/十六烷和支链基础油/聚α-烯烃（PAO）的线性模型，这些溶液被限制在云母表面之间，受到不同的施加载荷(L)。L = 3.3 mN时，十六烷中异硬脂酸和异硬脂酸T的粘度参数（bs）值分别为纯十六烷的七分之一和三十分之一。特别是十六烷中的异硬脂酸T，即使在L = 22.7 mN时，粘度参数bs值也较低，仅为纯十六烷的1 / 8。另一方面，在L = 3.3 mN时，PAO中异硬脂酸的bs值为纯PAO的一半，在L = 11.6 mN时，这种影响消失；PAO中的异硬脂酸T导致与纯PAO相似的行为。线性润滑剂的密集堆积结构，如十六烷被限制在表面之间，已知会导致高bs值，并且这种结构可能在支链脂肪酸添加剂的存在下受到干扰。对于支链基础油，如PAO，在约束下没有形成致密堆积状态，因此支链脂肪酸添加剂的影响不显著。该研究表明，添加剂的分子结构相对较小的差异对于有效减少摩擦非常重要，特别是在线性基础油的边界润滑制度中。图形抽象

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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.