Long‐Time Thermal Aging of Perfluoroalkoxy Polymers for Electrical Insulation: Structural and Physical Properties Evolutions

ABSTRACT Poly(tetrafluoroethylene‐ co ‐perfluorovinyl ether) copolymers, more commonly known as PFA, form a family of extrudable fluoropolymers used in replacement of PTFE for electrical insulation of high voltage aeronautic cables. This work focuses on the investigation of the influence of a long‐time exposure to accelerated thermal aging at two different temperatures on the physical properties of PFA. Results showed that the evolution of the physicochemical structure does not depend on the applied temperature, but rather is linked to the caused degradation. We observed a decrease in the melting temperature of about 2°C and melting enthalpy of about 28% of its initial value, which could be due to the scission of the polymer chains entailed by a depolymerization mechanism. Chemical aging, linked to such mechanism, led to a decrease in both the mechanical modulus (about 45% at 25°C) and static electrical conductivity of about 1 decade.