Organic friction modifiers (OFMs) are often used with zinc-dialkyl-dithio-phosphate (ZDDP) in engine oil formulations to reduce boundary friction while maintaining the anti-wear property of ZDDP. This study investigated the interaction between fatty acids and ZDDP. The results showed that the adsorption of fatty acids determines the friction coefficient when fatty acids are used alone. The friction coefficient was smaller when a denser fatty acid adsorbed layer was formed. Neutron reflectivity (NR) measurement revealed that, for a fatty acid-ZDDP combination, the fatty acid also contributes to friction behavior; a synergistic effect occurred only with a reduction in the interface metal thickness. These results suggest that the fatty acid-ZDDP combination promotes metallic soap formation, which reduces friction.

在发动机油配方中，有机摩擦改性剂 (OFM) 通常与二烷基二硫代磷酸锌 (ZDDP) 一起使用，以减少边界摩擦，同时保持 ZDDP 的抗磨损性能。本研究调查了脂肪酸与 ZDDP 之间的相互作用。结果表明，脂肪酸的吸附决定了单独使用脂肪酸时的摩擦系数。当形成更致密的脂肪酸吸附层时，摩擦系数更小。中子反射率 (NR) 测量表明，对于脂肪酸-ZDDP 组合，脂肪酸也有助于摩擦行为；只有在减少界面金属厚度时才会产生协同效应。这些结果表明脂肪酸-ZDDP 组合促进了金属皂的形成，从而减少了摩擦。