On the resistance of hydrophobic soil polymer coatings created by cold plasma polymerization

Institute of Geotechnical Engineering and Construction Management, Hamburg University of Technology, 21079 Germany

^* Corresponding author: clara.toffoli@tuhh.de

Abstract

Hydrophobic soils have natural or artificial origin. In this context, some techniques exist to turn into hydrophobic sand that was originally hydrophilic, as most soils in fact are. Its classical application is impermeabilizing structures where water percolation is not desired. In this paper, a new technique to achieve hydrophobicity is described. It consists of coating particles via cold plasma. The process is known to the industry, but its application in geotechnics is not yet described in literature. The monomers used were octafluorcyclobutane (C4F8) and 1H,1H,2H,2H-perfluoroctylacrilate (PFA-C6). For each monomer, the material was in the coating chamber during two different time spans and a sample was pretreated with oxygen. Different mechanical, thermal and hydraulic conditions were imposed to the samples in order to evaluate the resistance of the coating and its properties. The hydrophobicity was evaluated by means of Water Drop Penetration Time. Results indicate that longer time spans in the cold plasma chamber lead to a more hydrophobic material and that oxygen pretreatment on the sample is irrelevant. It was also observed that mechanical, hydraulic and thermal procedures influence the coating. These observations lead to optimization of the production process and to the understanding of how the material can be applied in the construction industry and what mechanical/hydraulic loads it can be subjected to.