Rheology of Olefinic Copolymer Layers Adsorbed on Solid Surfaces

Abstract

The rheology of two adsorbed layers of olefinic copolymers (OCPs) between two cobalt surfaces was investigated using a surface force apparatus (SFA). Each polymer layer is obtained by adsorption in a dilute solution of OCP and dispersant OCP (DOCP) in a 175 neutral solvent basestock at 24°C. The aim of these experiments is the mechanical characterization of the compressed polymer films. The hydrodynamic thickness R_H detected is compared with the thickness of the polymer layers L and the hydrodynamic radius R_H of the polymer coil in solution. All these distances, strongly related to the chemical structure of the polymer, indicate that the layers are not always homogeneous. For OCP, 0.55L ≈ L_H ≈ 2R_H, and for DOCP L ≈ L_H ≈ 2.7R_H. Finally the two layers present different inelastic behaviors. The DOCP layer presents a mesh more compact and more uniform than the OCP layer as indicated by the thickness measurements.

Presented as a Society of Tribologists and Lubrication Engineers paper at the STLE/ASME Tribology Conference in Kissimmee, Florida, October 8–11, 1995

KEY WORDS:

• Surface Films/Coatings
• Lubricant Rheology

Notes

Presented as a Society of Tribologists and Lubrication Engineers paper at the STLE/ASME Tribology Conference in Kissimmee, Florida, October 8–11, 1995