November / December 2019 NLGI Spokesman

The study of relationships of urea groups in polyurea greases and their properties

By Vijay Deshmukh & Chetan Pagare Standard Greases & Specialities Pvt. Ltd. Mumbai, India Abstract The “2017 NLGI World Grease Production Survey” indicates that the production of polyurea greases is growing slowly. Its popularity as multipurpose greases in various industrial and automotive applications is growing. They are used as excellent high temperature greases in steel plants and in many automotive applications. The commercially available polyurea greases are thickened mostly with diureas and tetraureas. The properties of polyurea greases depend upon their composition and manufacturing process.

The present paper studied the relationship between the number of urea groups in polyurea grease thickeners and the grease properties. Polyurea greases thickened with different numbers of urea groups such as diurea, tetraurea, hexaurea and octaurea were prepared in the laboratory with mineral oil. These greases were tested for their major properties. The effect of number of urea groups on the properties of polyurea greases was studied and discussed.

Introduction Although polyurea greases were known since the 1950s, their commercial production gained importance only in the early twentieth century. The major challenge in its large scale production was the handling and storage of toxic and hazardous raw materials used for their production. Even now the production of polyurea greases is restricted to a few major companies.

Polyurea greases have excellent high temperature properties and oxidation resistance. The absence of any metal ion in polyurea greases give them excellent oxidation stability and thereby very long life. These greases have very good water resistance and corrosion resistance properties. Their flow properties are also good and, hence, they are most suitable for centralised lubrication systems.

These properties make them a very good choice for high temperature applications in steel plants especially in continuous casting applications. Special thermostable polyurea greases were developed for such applications, which resulted in improvement in lubricity and reduction in wear and damage of bearings. (1) Polyurea greases are also popular for automotive applications such as wheel bearings, CV joints, ball joints, brake callipers, etc.

There are many patents on polyurea greases regarding their composition and method of preparation.

(2-10) . Normally, polyurea greases are prepared in open kettles. But it has been shown that polyurea greases can also be prepared in Stratco Contactor reactors. (11) The major components of polyurea grease are isocyanates and amines. By using different combinations of aliphatic or aromatic isocyanates and various amines, polyurea greases with desired properties can be produced. Thus, polyurea chemistry offers an opportunity to develop thickeners for greases with diverse properties. (12) - 22 VOLUME 83, NUMBER 4