Novel polymer grease microstructure and its proposed lubrication mechanism in rolling/sliding contacts

A novel polymer grease micro-structure is revealed using scanning electron microscopy (SEM), cryogenic scanning electron microscopy (cryo-SEM) and transmission electron microscopy (TEM). The structure consists of amorphous polypropylene nano-particles uniformly distributed in the base oil. This novel microstructure has never been documented before. Rheology shows that there is no irreversible shear-thinning. The grease shows excellent stability and flow behaviours. In the absence of crystallization and a network thickener structure, it has a potential for use at extremely low start-up temperatures. Spherical roller bearing (SRB) testing shows excellent lubricating performance and the potential for lowering friction in comparison with benchmark greases. It is hypothesized that the grease behaves as a highly stable nano-fluid allowing abundant oil replenishment into the rolling contact, whereby nanoparticles are released with the base oil in the contact.