Molecular Disaggregation Process of PTFE Using Sodium Chloride: A Study by Infrared Spectroscopy

Mechanical recycling of polytetrafluoroethylene (PTFE) has long been a crucial matter in fluorocarbon chemistry. Since the molecular aggregation of PTFE is outstandingly strong, fluorocarbon solvents are believed to be necessary for the disaggregation of PTFE, but they should not be used as much as possible because of concerns about environmental impact. Recently, a new technique using solid sodium chloride with the aid of planetary ball milling, instead of using fluorocarbon solvents, has been proposed, and this simple technique works powerfully indeed for the purpose, as confirmed by a significant decrease of crystallinity. Here, we show that the molecular disaggregation process of PTFE using sodium chloride is revealed in detail by infrared (IR) spectroscopy. The spectra clearly show that PTFE is readily crushed into fine particles, and molecular disaggregation within the particles is also recognized. These changes are not found at all in a process that does not use sodium chloride. In addition, the generation of helical defects in perfluoroalkyl chains is also found, which is correlated with molecular disaggregation. In this manner, IR spectroscopy has been found to be a useful tool in providing us rich information on the molecular disaggregation process of PTFE across three different hierarchical structures.