Wu, Han; Wang, Jiabei; Guo, Zhaoyang; Du, Hengrui; Hu, Wenjing; Xu, Jian; Wang, Jing; Lu, Hengyi; Li, Jiusheng

TRIBOLOGY INTERNATIONAL

2025, ,

Wu, Han; Wang, Jiabei; Guo, Zhaoyang; Du, Hengrui; Hu, Wenjing; Xu, Jian; Wang, Jing; Lu, Hengyi; Li, Jiusheng

Friction causes mechanical parts' wear and even failures. Using lubricating grease can effectively diminish the friction for bearing and associated components. However, along with the operation, the temperatures increase significantly reduce the viscosity of the base oil and weaken the structural stability of the thickener network, resulting in excessive oil separation, and ultimately impacting its lubrication performance. Herein, three types of polyurea grease with different thickener structures were synthesized using Metallocene poly (alpha-olefin) oil (mPAO) with varied polymerization degrees and presynthetic thickener. Structural characterizations indicate that increasing the polymerization degree of mPAO facilitates the formation of longer thickener fibers and more loose thickener networks. Through an integrated analysis of its network cross-linking degree and oil separation behaviors, we found that the polyurea grease prepared from the high polymerization degree base oil (mGH), although possessing the weakest base oil binding capacity, can generate a significant number of short fibers and establish new cross-linking points under shear, thus maintaining structural integrity. This mechanism enables the thickener network to sustain the continuous release of base oil to the friction surface under evaluated temperature, thereby promoting the formation of a robust lubricant film during continuous operation. These results will provide new theoretical insights for the development of high-performance greases.