title: Resistance of POSS Polyimide Blends to Hyperthermal Atomic Oxygen Attack.
abstract: Copolymers of polyhedral oligomeric silsesquioxane (POSS) and polyimide (PI) have shown remarkable resistance to atomic oxygen (AO) attack and have been proposed as replacements for Kapton on the external surfaces of spacecraft in the harsh oxidizing environment of low Earth orbit (LEO). POSS PI blends would be an economical alternative to the copolymers if they also resisted AO attack. Thus, blends of trisilanolphenyl (TSP) POSS and PI with different weight percentages of the Si7O9POSS cage were cast into films and exposed to a hyperthermal AO beam, and they were characterized in terms of their recession, mass loss, surface morphology, and surface chemistry. In order to compare the AO resistance of the blends with POSS PI copolymers, samples of previously studied copolymers were also investigated in parallel with the blends. For all POSS PI materials, the AO resistance increased with increasing AO fluence and with increasing POSS cage loading. At similar POSS cage loadings and exposure conditions, the TSP POSS PI blends showed comparable erosion yields to the POSS PI copolymers, with specific samples of blends and copolymers achieving erosion yields as low as 0.066 × 10-24cm3atom-1with an AO fluence of 5.93 × 1020O atoms cm-2. SEM and XPS analyses indicated that passivating SiOxlayers were formed on the surfaces of all POSS-containing polymers during AO exposure. Thus, a TSP POSS PI blend is proposed as a low-cost variant of a POSS polyimide for use in extreme oxidizing environments, such as LEO.
authors.affiliation: Department of Chemistry and Biochemistry, Montana State University , 103 Chemistry and Biochemistry Building, Bozeman, Montana 59717, United States.
authors.forename: Min
authors.initials: M
authors.lastname: Qian
authors.affiliation: Department of Chemistry and Biochemistry, Montana State University , 103 Chemistry and Biochemistry Building, Bozeman, Montana 59717, United States.
authors.forename: Vanessa J
authors.initials: VJ
authors.lastname: Murray
authors.affiliation: Department of Chemistry and Biochemistry, Montana State University , 103 Chemistry and Biochemistry Building, Bozeman, Montana 59717, United States.
authors.forename: Wei
authors.initials: W
authors.lastname: Wei
authors.affiliation: Department of Chemistry and Biochemistry, Montana State University , 103 Chemistry and Biochemistry Building, Bozeman, Montana 59717, United States.
authors.forename: Brooks C
authors.initials: BC
authors.lastname: Marshall
authors.affiliation: Department of Chemistry and Biochemistry, Montana State University , 103 Chemistry and Biochemistry Building, Bozeman, Montana 59717, United States.
authors.forename: Timothy K
authors.initials: TK
authors.lastname: Minton
keywords: POSS; atomic oxygen; hyperthermal; low Earth orbit; polyhedral oligomeric silsesquioxane; polyimide