An Investigation of the Resistance of Polyhedral Oligomeric Silsesquioxane Polyimide to Atomic-Oxygen Attack

Abstract

Hybrid inorganic/organic polymers have been prepared by copolymerizing a polyimide having the same chemical repeat unit as Kapton with an open-cage polyhedral oligomeric silsesquioxane (POSS). These POSS/polyimide hybrid polymers are Kapton-like polymers containing POSS nanoparticles that are chemically bound into the polymer chain. Samples of these POSS polyimides, as well as polyimide controls, have been exposed to a hyperthermal 0-atom beam that is produced by a laser-detonation source. Exposed and unexposed surfaces have been characterized by surface profilometry, atomic force microscopy, and X-ray photoelectron spectroscopy The data indicate that the POSS-containing polyimides have significantly lower erosion yields than Kapton, because they form a surface SiO2 layer which passivates the surface and protects the underlying polymer from further 0-atom attack. These results suggest promise for the use of a POSS polyimide polymer as a "drop-in" replacement for Kapton on spacecraft operating in the low-Earth orbital environment.

Synthesis and Characterization of Space-Survivable POSS-Kapton (Trademark) Polyimides (Preprint)

“…[29] For various exposures, the step heights (or etch depths) of POSS-PI films were plotted as a function of the step height of the Kapton H ® film. [23] The derivative functions indicated that the 3.5 and 7.0 wt % Si 8 This paper is declared a work of the U.S. Government and is not subject to copyright protection in the United States and increased in depth to 1.4 µm after the second exposure. The top of the SiO 2 -coated Kapton HN ® image was exposed to AO and only had erosion in the scratched area with unaffected neighboring silica-coated Kapton HN ® , demonstrating the effects of damage to silica coatings on Kapton ® .…”

“…The beam was produced by the laser detonation source previously described. [9,23] Three samples of each type were exposed to 100k DISTRIBUTION A. Approved for public release; distribution unlimited.…”

“…[9,23] The hyperthermal beam contains neutral O-atoms and molecular oxygen, with an ionic component of 0.01%. The mole fraction of AO in the beam was above 70 % and, for some exposures, above 90 %.…”

Properties and Improved Space Survivability of POSS (Polyhedral Oligomeric Silsesquioxane) Polyimides

“…The surface layer of 10 and 20 wt% POSS-Polyimide film has been characterized using XPS before and after incremental exposures to the hyperthermal O-atom source. [19] Details of this study were described by Minton et al [14] XPS survey spectra of C(1s) and Si(2p) peaks were obtained from 0, 10, and 20 wt% POSS-polyimide surface before and after AO exposures, and the Si(2p) spectra are shown in Figure 4. Following exposure of 20wt% POSS polyimide to 100 kpulses of the O-atom beam, the Si(2p) peak shifted from a binding energy of 102.3 eV corresponding to the silsesquioxane (Si 2 O 3 ) to 104 eV approximately corresponding to the formation of SiO 2 .…”

“…[14] The average of 30 step height of the etched and unetched portions was determined by surface profilometry. These measurements were obtained with the use of a Dektak 3 (Veeco Metrology Group, Santa Barbara, CA) surface profilometer.…”