The effect of simulated low earth orbit radiation on polyimides (UV degradation study)

Conference · Wed Feb 01 04:00:00 EST 1995

OSTI ID:42770

Forsythe, J S; George, G A; Hill, D J.T.; Odonnell, J H; Pomery, P J; Rasoul, F A

UV degradation of polyimide films in air and vacuum were studied using UV-visible, ESR, FTIR, and XPS spectroscopies. The UV-visible spectra of polyimide films showed a blue shift in the absorption compared to Kapton. This behavior was attributed to the presence of bulky groups and kinks along the polymer chains which disrupt the formation of a charge transfer complex. The UV-visible spectra showed also that UV irradiation of polyimides result extensively in surface degradation, leaving the bulk of the polymer intact. ESR spectra of polyimides irradiated in vacuum revealed the formation of stable carbon-centered radicals which give a singlet ESR spectrum, while polyimides irradiated in air produced an asymmetric signal shifted to a lower magnetic field, with a higher g value and line width. This signal was attributed to oxygen-cenetered radicals of peroxy and/or alkoxy type. The rate of radical formation in air was two fold higher than for vacuum irradiation, and reached a plateau after a short time. This suggests a continuous depletion of radicals on the surface via an ablative degradation process. FTIR, XPS, and weight loss studies supported this postulate. An XPS study of the surface indicated a substantial increase in the surface oxidation after irradiation in air. The sharp increase in the C-O binding energy peak relative to the C-C peak was believed to be associated with an aromatic ring opening reaction.

• Research Organization: National Aeronautics and Space Administration, Hampton, VA (United States). Langley Research Center
• OSTI ID: 42770
• Report Number(s): N--95-23896; NASA-CP--3275-PT-2; L--17430B-PT-2; NAS--1.55:3275-PT-2; CONF-9311137--
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ABLATION
DECOMPOSITION
IMIDES
OXIDATION
PHYSICAL RADIATION EFFECTS
TESTING
THIN FILMS
ULTRAVIOLET RADIATION