Investigation on stability of Teflon under extreme conditions: analysis of surface degradation

This paper investigates the effect of a prolonged acid attack on the surface of PTFE by Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). PTFE is a very non-reactive polymer, partly due to the strength of carbon–fluorine bonds, and for this reason it is often used in containers and pipework parts in contact with reactive and corrosive chemicals. The PTFE under analysis is commercialized by two manufacturers in form of Teflon adhesive tapes. These tapes are used as gaskets in a tyre moulds cleaning plant, based on different acid baths and ultrasonic waves. In particular, PTFE gaskets show anomalous phenomena of surface degradation in a relatively short operation time. Nevertheless, even considering the combined effect of ultrasonic waves, temperature, humidity and acid attack, PTFE properties nominally exclude the risk of the extreme erosion phenomena as observed. The present experimental research aim at investigating this contradiction. In this study PTFE samples have been treated with different mixes of acids, in order to investigate the different aging effects. The infrared and thermal analysis has permitted the characterization of PTFE surface and core properties after acid attack, providing evidence of the degradation phenomena. In particular, the different acid treatments adopted for the aging of gaskets have highlighted not only the different response of the PTFE matrix, but also differences between manufacturers.