Characterization of microfibril development on PTFE surface during hot imprinting process and its application for oil–water separation

The importance of oil–water separator has increased due to environmental pollution caused by marine accidents. Many studies related to fabrication method of superhydrophobic surface have been conducted because those functional surfaces are an important component used in oil and water separators. However, processes that can be applied to large area and mass production still exist as limitations. In this paper, superhydrophobic surfaces were fabricated on polytetrafluoroethylene (PTFE) surface by hot imprinting. To impart rough surface morphology to PTFE surface, hot imprinting process using an electrical discharge textured (EDT) mold was conducted. It was found that undercut of a discharge crater on the EDT surface induced tensile deformation of PTFE surface during the hot imprinting process resulting in microfibril development. As a result, PTFE surface had rough morphology consisting of replicated EDT surface and microfibril network. Imprinted PTFE sheets showed high water contact angles about 154.3° with low contact angle hysteresis about 1.4°. Additionally, the effects of process temperature and roughness of the EDT mold on microfibril formation were investigated. It was found that microfibril formation is activated when the process temperature reaches glass transition temperature (115 °C) of PTFE. The PTFE sheets for oil–water separation were prepared by hot imprinting and followed by additional drilling process. The optimal hole diameter with respect to efficiency of oil–water separation was determined through experiments and separation of oil and water was effectively conducted.