Direct Photo-Etching and Surface Modification of Polytetrafluoroethylene by Synchrotron Radiation

Abstract

Micromachining of various polytetrafluoroethylene (sintered PTFE, non-sintered PTFE and expand PTFE) using synchrotron radiation (SR) direct photo-etching has been carried out, and also the etched surface was studied by various analyses. The thin sintered (10μm) and expand (80μm) PTFE films were piled up, and the layered PTFE and non-sintered PTFE (1.2mm) irradiated by SR below the melting temperature, in order to clarify the degree of chemical and physical changes according to the depth from the etched surface. SR irradiated films were examined by 19F solid-state magic-angle spinning (MAS) NMR spectroscopy and differential scanning calorimetric (DSC) analysis. The results showed that the modification by SR irradiation depended on the depth from the surface: within about 60μm from the surface, the network structure formation would be induced even in its solid state; in deeper regions, the chain scission would be dominant. Furthermore, SR was irradiated for non-sintered PTFE with different molecular conformation, compared with usual PTFE. It was found that non-sintered PTFE was also crosslinked in the surface region. Moreover, the sintered and non-sintered PTFE could be etched well. In the case of non-sintered PTFE, the distance of the non-etched remaining structures shrank by heat-treatment at 360°C. The shrinking was about 20%.