Adhesion associated with solids and liquids
This work was done to study the relation between the lateral adhesive force, f, and time t. The experiments were performed on different substrates using different liquids. Both soft and rigid surfaces were checked to find whether there is an effect of waiting time on lateral adhesive force. Experiments were performed on both coated as well as uncoated surfaces. The lateral adhesive force was measured using the tilting plate method. The drop motion was recorded using a PG Goniometer. The force, f, required to slide a drop past a surface is shown to be a function of the time, t, the drop waited on the surface prior to the commencement of sliding along it. The “rest time” effect was observed in different systems, which suggests that this phenomenon is general. It is shown that df/dt is never negative. As the resting time increases, df/dt decreases towards zero (plateau) as time approaches infinity. The reason for the change in retention force with time is a deformation of the surface that results from the Laplace pressure induced by the drop on the surface as expressed by the unsatisfied normal component of the Young's equation. From the experimental results it was observed that this phenomenon was more pronounced for softer materials than for hard materials.
0794: Materials science