Effects of Vacuum Ultraviolet Radiation on Thin Polyimide Films

Abstract

This paper describes the vacuum ultraviolet (VUV) radiation durability screening testing of thin (12.7-25.4 µm) polyimide films proposed for use on the Next Generation Space Telescope (NGST) sunshield. Materials included in this screening test were Kapton ® E, Kapton ® HN, Upilex ® S, CP1, CP1 with vapour deposited aluminium (VDA) on its back surface, and CP2 with a VDA coating on its back surface. Samples were exposed to approximately 1000 equivalent sun hours (ESH) of VUV radiation and examined for changes in solar absorptance, thermal emittance, ultimate tensile strength, and elongation at failure. Changes in the solar absorptance were observed for some materials, and, additionally, significant changes in spectral reflectance were observed in the ultraviolet to visible wavelength region for all of the polyimide materials tested. Changes in the ultimate tensile strength and elongation at failure were within the experimental uncertainty for all samples. Longer exposures are needed to verify the observed trends and to develop performance predictions for these materials on the NGST sunshield.

Preparation and properties of polyimide nanocomposites with negative thermal expansion nanoparticle filler

“…9. The base PI, LaRC-CP1, had a distinct yield point and broke at a relatively high strain rate because of the presence of the flexible ether and hexafluoropropyl groups in the main PI structure [52]. The addition of rigid nanofillers to the polymer matrix produced composites that were brittle with lower strain at break compared to the base PI.…”

Photodegradation of PEEK sheets under tensile stress

“…Photodegradation of polymeric material has been extensively investigated, and most studies of deterioration were generally conducted under UV irradiation [1][2][3][4][5][6][7][8][9][10][11]. Polymers are used under stress in most practical applications; therefore, several studies of the combined effect of photo-oxidation and mechanical stress have been discussed [12][13][14][15][16].…”

Review of Radiation-Induced Effects in Polyimide

“…VUV exposure of PI film has not been shown to significantly affect its mechanical properties. For example, the irradiation of PI film, intended to serve as a sunshield in the next generation space telescope (NGST) mission, with VUV radiation of 1000 equivalent sun hours, caused changes in the ultimate tensile strength and elongation of failure of all samples within the experimental uncertainty [137].…”

“…Irradiation of PI film with VUV radiation (5-200 nm) led to a darkening of the PI material and is attributed to surface carbonification, causing significantly reduced reflectance of PI film in the 250-500 nm spectral region [137]. The VUV-induced breakage of the ether bridge oxygen and carbon-nitrogen bonds leads to the high concentration of benzene group near the surface of PI film [113].…”