Contact of two carbon surfaces covered with a dispersant polymer

Using a surface force apparatus (SFA), me have studied, first the adhesive force between two smooth amorphous carbon surfaces in air, and second, the repulsive force due to the contact of two blush polymer layers adsorbed on carbon surfaces. Adhesion in dry air is compared to that due to the effect of a small meniscus formed in humid air and the partial wetting of a large water meniscus. Dispersive and acid-base contributions of carbon surfaces are also determined, using Fowkes analysis. The adsorption of a polyisobutenesuccinimide (PIB) in dilute solution with hydrocarbon solvent at 25 degrees C, and the resulting interactions between carbon surfaces are also characterised with the SFA. Our results show that this dispersant polymer on a carbon surface forms a 5.5 nm thick anisotropic brush leger. This anisotropy is detected mechanically and compared with that of other polymer or surfactant. The ability of PIE molecules to adsorb on carbon particles and thus stabilize them in the hydrocarbon solution, is of great implication in lubrication technology. The results clarify that this additive function by steric stabilization mechanism and not by electrostatic repulsion The results provide a basis for understanding the mechanism of action of of polyisobutenesuccinimides widely used as dispersant additives in lubricants.