Cross-sectional observation of a weak boundary layer in polytetrafluoroethylene (PTFE) using scanning electron microscope

A weak boundary layer (WBL), at the surface of polymers, causes poor adhesion, but such a WBL has not been characterized or quantified. In this study, to characterize a WBL of polytetrafluoroethylene (PTFE), we observed a cross-section of PTFE using a scanning electron microscope and compared the surfaces and bulk sides. We observed voids on the surface of the PTFE but not on the bulk side. These voids existed up to 5 mu m from the outermost surface of the PTFE. We defined a WBL by the presence or absence of voids and then concluded that the thickness of the WBL in PTFE was of the order of a single micrometer.