Effect of air and vacuum storage on the tensile properties of x-ray exposed aluminized-FEP

Metallized Teflon (R) FEP (fluorinated ethylene propylene), a common spacec raft thermal control material, which forms the exterior layer of the Hubble Space Telescope (HST) has become embrittled and suffers from extensive cra cking. Teflon (R) samples retrieved during Hubble servicing missions and fr om the Long Duration Exposure Facility (LDEF) indicate that there may be co ntinued degradation in the tensile properties over time. An investigation h as been conducted to evaluate the effect of air and vacuum storage on the m echanical properties of x-ray exposed FER Aluminized-FEP (Al-FEP) tensile s amples were irradiated with 15.3 kV Cu x-rays and stored in air or under va cuum for various time periods. Tensile data indicate that samples stored in air display larger decreases in their tensile properties than for samples stored under vacuum. Air-stored samples developed a hazy appearance, which corresponded to a roughening of the aluminized surface. Optical property ch anges were also characterized. These findings indicate that air exposure pl ays a role in the degradation of irradiated FEP, therefore proper sample ha ndling and storage is necessary with materials retrieved from space.