Microgravity Expulsion of PTFE Spheres from Water: An Experimental Study

This paper presents the hypothesis and experimental results of expulsion of spheres that are made up of polytetrafluoroethylene (PTFE), also known as Teflon, and Teflon spheres layered with superhydrophobic substances, from water under microgravity conditions. The microgravity was simulated in a drop tower. The microgravity tests were conducted in the 2.2 Second Drop Tower at the NASA Glenn Research Center in Cleveland, Ohio. The experimental test objects chosen were: a) the unmodified PTFE sphere to serve as the base case (30 mm diameter); b) a PTFE sphere of same diameter layered with butyl rubber (25 mm of PTFE and 5 mm of butyl rubber); and c) a PTFE sphere of same diameter layered with paraffin (25 mm of PTFE and 5 mm of Paraffin). We hypothesized that the PTFE sphere with a butyl rubber coating would rise the highest distance in the drop chamber due to its super-hydrophobicity as determined by the contact angle of the objects. We tested the effect of microgravity on fully submerged and partially submerged objects in water. The expulsion data from our experimental runs in both fully and partially submerged protocols is presented, as well as our analysis and recommendations. Our test resulted in measurable reduction of the hydrophobicity effect while exposed to microgravity. We propose new research regarding a compounding effect of hydrophobicity based on surface properties and roughness of substances