Predicting and measuring repulsive van der Waals forces for a Teflon AF™–solvent–α-alumina system

The force interaction of an α-alumina particle against Teflon AF™ in the presence of several non-polar and polar solvents was quantified. Solvents were chosen based on calculation of a negative Hamaker constant, indicating a repulsive van der Waals interaction. These results were compared to those predicted by theoretical models for van der Waals forces. Measured forces for the non-polar solvent interactions are comparable to theoretical predictions, whereas the polar solvent interactions show repulsive forces between one and two orders of magnitude smaller than those predicted. In the case of water, surface charges were large enough to completely counteract the repulsive van der Waals forces and lead to an attractive force interaction. This minimization of repulsion, and even attraction, can be predicted by DLVO theory.