Colloidal Physicochemical Properties and Variation Mechanisms of Lithium Complex Grease under Limited Operating Temperature

Abstract

Abstract This study aims to investigate the colloidal physicochemical properties and variation mechanisms of lithium complex grease after heating at a limited operating temperature (180°C). Experimental lubricating grease samples were prepared by static heating in the laboratory for different times to simulate the limited operating temperature. The variations in grease mass loss and consistence were studied. Rheological behavior tests were carried out to explore the structural strength and structural recovery properties of all grease samples by using a continuous shear and oscillatory shear rheometry model of rotational rheometer. The fibrous microstructure was investigated by field emission scanning electron microscope, and infrared spectra were recorded using a Fourier transform infrared spectrometer. A structural evolution model of grease colloidal dispersion system was established and used to elucidate the variation mechanism of grease colloidal physicochemical properties under limited operating temperature conditions. The colloidal property of lithium complex grease gradually changed with prolonged heating time. The consistence of grease increased with increasing heating time. The typical shear yield phenomenon became less obvious, and the structural recovery property evidently weakened obviously with prolonged heating time. The variation mechanism of grease colloidal physicochemical properties could be mainly attributed to the thickener oxidation of grease. Results provide experimental support for grease application and failure analysis under harsh conditions.