(174i) Tribology of PVA Borax Gel on Silanized Silica

The forces that are required to slide drops on surfaces (retention forces) are known to increase with time that the drop rests on the surface. Here we present a system in which the opposite happens; the retention force decreases with time the drop rests on the surface; and after following a minimum in the retention force, it rises again. This peculiar phenomenon is explained by the nature of the components present in the system. The gel drop is made of an aqueous solution of polyvinyl alcohol (PVA) and disodium tetraborate (borax) , and it rests on a silanized silica surface.We explain this phenomenon correlating the physical nature of the gel and the mechanism that drives its motion on the surface. Sequential events like the breakage of the polymer molecules while the gel has been placed on the surface, and its adhesion to the surface where a reduction in the solid liquid interfacial tension happens because of coffee ring effect, and a subsequent re-joining of the broken polymer molecules increasing the robustness of the gel and its adhesion to the solid surface explain the bizarre behavior of this gel on silanized silica.