*Article* **Investigation of Tribological Behavior of Lubricating Greases Composed of Different Bio-Based Polymer Thickeners**

**Seyedmohammad Vafaei 1,\*, Dennis Fischer 1, Max Jopen 2, Georg Jacobs 1, Florian König 1 and Ralf Weberskirch 2**


**Abstract:** One commonly used lubricant in rolling bearings is grease, which consists of base oil, thickener and small amounts of additives. Commercial greases are mostly produced from petrochemical base oil and thickener. Recently, the development of base oils from renewable resources have been significantly focused on in the lubricant industry. However, to produce an entirely bio-based grease, the thickener must also be produced from renewable materials. Therefore, this work presents the design and evaluation of three different bio-based polymer thickener systems. Tribological tests are performed to characterize lubrication properties of developed bio-based greases. The effect of thickener type on film thickness and friction behavior of the produced bio-based greases is evaluated on a ball-on-disc tribometer. Moreover, the results are compared to a commercial petrochemical grease chosen as benchmark.

**Keywords:** bio-based grease; grease lubrication; film thickness; friction measurements; polyurea thickener
