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 µm 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. Polytetrafluoroethylene (PTFE) has a weak boundary layer (WBL) on the surface. A cross-section of PTFE was observed using a scanning electron microscope for investigating the difference in morphology between WBL and bulk layer. Large voids of 0.5–2.0 µm in diameter were observed on the surface side of PTFE but not on the bulk side. These voids existed up to approximately 5 µm from the outermost surface of the PTFE. This result indicated that the thickness of WBL of PTFE was in the order of single µm.