Thermal and thermo-oxidative degradation of tetrafluoroethylene–propylene elastomer above 300 °C

Abstract

The research on the applicability of elastomeric sealing materials in geothermal environments has focused on changes in physical properties, and our understanding of the chemical changes remains lacking. This work investigates the thermal and thermo-oxidative aging behaviors of tetrafluoroethylene–propylene elastomer (FEPM) at temperatures above 300 °C. During thermal aging, the polypropylene (PP) molecular chain that is not adjacent to the polytetrafluoroethylene (PTFE) component breaks and thus causes the removal of partial saturated hydrocarbons. During thermo-oxidative aging, the appearance of O2 promotes the oxidative scission of the PP component and the removal of the PTFE component, thereby generating new carbonyl-containing substances and double bonds. Therefore, the degrees of mechanical and thermal property damages caused by thermo-oxidative aging are much higher than those caused by thermal aging. In addition, the triallyl isocyanurate crosslinked structure degrades during thermal and thermo-oxidative aging, resulting in the destruction of the crosslinked network. The analysis of the degradation mechanism of FEPM allows chemical changes to be correlated with physical modifications and provides theoretical guidance for the future development of fluoroelastomers.