The influence of mechanical shearing on the thickener microstructure and properties of Polyurea greases

Abstract

Polyurea (PU) greases have found widespread applications in harsh working conditions. While the influence of PU molecule and thermal treatment condition on the microstructure and properties of PU greases has been well elucidated, the impact of mechanical shearing remains unclear. This study explored how mechanical shearing during production affects the structure and properties of PU grease made from octylamine and 4,4′-diphenylmethane diisocyanate. It was found that static heat treatment leads to nanotube structures, while stirred heat treatment creates twisted fibers. Shearing flow is shown to influence the formation of these structures. The nanotube PU grease has lower consistency and better lubrication for high-speed conditions, while the twisted fiber grease offers higher consistency and stability, suited for boundary lubrication.