Effects of MeV proton bombardment in thin film PFA and FEP polymers

The polymers tetrafluoroethylene-per-fluoromethoxyethylene (PFA) and tetrafluoroethylene-hexa-fluoropropylene (FEP) are widely used in aerospace engineering applications. In medical physics, they are used as substitutes for some human body tissues replacement and as radiation dosimeters. In the aerospace as in space field, they are used because they resist damage from the high of ionizing radiation met in space. When a polymer is exposed to ionizing radiation, it can suffer damage according to the type, energy and intensity of the radiation. In order to determine the damage mechanism of these polymers, they were bombarded with 1 MeV protons at constant current and fluence from 1×1011 to 1×1016 ions/cm2. The emission of chemical species was monitored with a residual gas analyzer (RGA) during bombardment. Results from FEP and PFA show that the CF3 is the specie preferentially emitted. The bombarded films were also analyzed with optical absorption photospectrometry (OAP), micro-Raman and Fourier transform infrared (FTIR) showing quantitatively the chemical specific evidence from the damage caused by the proton bombardment for each polymer. Our results show that damage to polymer surfaces is detectable at low fluence but damage that compromises applications in dosimetry occur only for fluence greater than 1015 protons/cm2.