Grease composition influence on friction & starvation

Nowadays, grease lubrication is frequently used in rolling element applications such as bearings or constant velocity joints. The advantage of grease is to supply lubrication to the application without leaking thanks to its consistency. Nevertheless, starvation can occur leading to damage such as scuffing. In the present study, starvation is analyzed using the Starvation Degree parameter through tests with different operating conditions and different types of greases.

OBTAINING AND PROPERTIES OF COMPOSITIONS OF UREA GREASES AND THEIR COMPONENTS ON THE BASIS OF VEGETABLE OILS

Background. In recent years, requirements for the properties of lubricants and their components are increasing. Attention is paid to the impact of lubricants on the environment. Urea greases fully meet the high requirements for the properties of lubricants. The development of greases of this class and vegetable oil-based additives should solve the environmental problems of their use. Objective. The purpose of the paper is development of urea greases and their components using raw materials of plant origin. Methods. A number of protective additives to lubricants were obtained by epoxidation of vegetable oils and introduction of nitrogen-containing fragments on the carbonyl group and epoxy ring. Amidation of triacylglycerides of vegetable oils with ethylenediamine synthesized monoaminoamides of fatty acids of linear structure. Urea thixotropic systems are synthesized by the interaction of polyisocyanate with fatty acid monoaminoamides in petroleum oil. Synthesized additives in various quantities were introduced into the composition of the investigated products in order to check the operational properties of the finished greases. Results. The obtained greases are characterized by a high level of mechanical and colloidal stability. Their composition and chemical structure were established by a set of spectrometric methods of analysis. The upper temperature limit of application of the synthesized urea in the range of 150–200 °С is established by the method of derivatographic analysis. It is established that the combination of urea thickener and vegetable oil-based additives allows obtaining urea greases with high thermal stability, improved protective and antioxidant characteristics. The use of environmentally friendly oleochemical products in the composition of the thickener and lubricant additives improves the biodegradability of the developed grease composition. Conclusions. It is shown that the proposed series of vegetable oil transformations allows obtaining ready-made compositions of urea greases and their components using raw materials of natural origin. The obtained products have satisfactory operational properties and according to some indicators industrial analogues prevail. This allows us to recommend the developed urea oils as substitutes for commercial products.

THE EFFECT OF THE TYPE OF WALL MATERIAL AND GREASE COMPOSITION PAIRING ON SHEAR STRESSES IN BOUNDARY LAYER

The paper presents the results of research on the influence of fillers introduced into plastic greases on the rheological properties of the boundary layer of the resultant lubricant compositions. The fillers were PTFE and MoS2 powders. They are added to lubricants to improve their tribological properties; however, these fillers also affect the rheological properties of the composition. This affects the change of the shear stress value in the lubricant during its flow in the lubrication system. Knowledge of this value, especially during the flow of the lubricant composition in the boundary layer, has a significant impact on the operation of automated central lubrication systems in which these compositions can be used. Measurements were carried out by means of a rotary rheometer (Rheotest 2.1). Tests were performed on lithium and bentonite greases (without additives) as well as compositions of these greases containing various percentage of the fillers mentioned above. Test results showed that both the type of grease and the type of filler introduced into this grease affect the rheological properties in the boundary layer of the produced lubricating compositions.

Comparison of Several Common Types of Grease Performance Based AR 2000ex Remoter

Different substrates grease composition due to differences in their varying degrees of change in viscosity after shearing studied the rheological properties of three different substrates grease. Used AR2000ex rheometer, investigated the effects of different sessions on the rheological properties of the grease. It was found that the stability of lithium grease from the grease either stops working, or their work situation by cutting lubrication properties, are superior to calcium-based grease and urea-based grease. Urea-based grease on the shear sensitivity is smaller relatively than lithium and the recovery of viscosity after being subjected to continuous shear weak, easily lost during use based the grease flow curves with Herschel-Bulkley model, and the impact performance of the grease thixotropic grease is yield stress.