Polytetrafluoroethylene or PTFE is a synthetic fluoropolymer of tetrafluoroethylene. This material is known for its chemical resistance, thermal stability and excellent hydrophobicity. PTFE is a simple polymer consisting of the two elements carbon and fluorine. The covalent compounds C–C and C–F are extremely strong. In addition, fluorine is the most electronegative element in the periodic table, which does not release its electrons. For this reason, PTFE has a low surface energy. High surface energy liquids, such as e.g. Water, difficult to wet the surface, which leads to the good hydrophobicity of PTFE. In a special manufacturing process, expanded PTFE membranes (ePTFE) are produced, which have a highly compressed structure and nevertheless an 85% porosity. These membranes are very breathable and defined pores.