Impact of polyurea structure on grease properties

Abstract

The thickener structure of polyurea grease has a crucial effect on its properties. Therefore, it is very important to study the relationship between a thickener structure and physical and performance properties. In this study, polyurea greases were synthesised, having a different number of urea groups in per polyurea thickener molecule. Properties such as dropping point, penetration, oil separation, shear stability and four-ball wear and extreme pressure (EP) were evaluated. The result shows that properties of polyurea grease vary with the number of urea group per polyurea molecule. Based on molecular theory, the mechanisms explaining these effects are briefly discussed.

Improving the lubrication and anti-corrosion performance of polyurea grease via ingredient optimization

“…| https://mc03.manuscriptcentral.com/friction of thickener that is polymerized by urea compounds [10,11]. Based on the amount of carbamido contained in a polyurea thickener, it can be divided into diurea or tetraurea based on the proportion and structure of reactants [12]. Nitrogen atoms with lone pair electrons enhance the polarity of urea compounds, which makes the PUG possess excellent affinity with metals.…”

“…Considering the importance of the thickener to the performance of grease, numerous scholars have focused on the microstructure of thickener to improve the performance of PUG. Liu and Sun [12] illustrated that there is a higher number of urea groups in the polyurea thickener molecule, and the PUG has superior performance, such as higher dropping point, lower oil separation, better shear stability, and initial wear load. Lyadov et al [24] investigated the effect of base oil viscosity and the different lengths of hydrocarbon substituent in the diurea thickeners on the physicochemical property and the tribological performance of PUG.…”

“…The stretching vibration peak of the C=O bond appeared at 1,630 cm 1 . The appearance of these bonds clearly demonstrated the existence of the carbamido in the polyurea thickener [12,13,23].…”

Microscopy of Polyurea Grease

“…The microstructure of polyurea greases, the most prevalent non-soap grease variety, has been typically reported to consist of "platelets" (Cyriac et al, 2016), fibers (Liu & Sun, 2010), and 3D network structures (Fan et al, 2018). However, the sample preparation of the polyurea greases for microscopy has usually involved the removal of the base oil or is not described in enough detail to replicate the results.…”

Comparative study on corrosion resistance and lubrication function of lithium complex grease and polyurea grease

“…The rheology and anti-wear properties of PUG were also investigated via using sebacic acid ester and esters of polyols as a base oil [26]. The effect of thickener structure on the performance of PUG was also evaluated [27]. Above all, although a large amount of literature reported the relationship between performance characteristics and ingredients/ structure of the two greases, the salt-spray resistance of grease has never been investigated thus far [28].…”