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

Abstract

Kapton polyimide (PI) is widely used on the exterior of spacecraft as a thermal insulator. Atomic oxygen (AO) in lower earth orbit (LEO) causes severe degradation in Kapton resulting in reduced spacecraft lifetimes. One solution is to coat the polymer surface with SiO2 since this coating is known to impart remarkable oxidation resistance. Imperfections in the SiO2 application process and micrometeoroid/debris impact in orbit damage the SiO2 coating, leading to erosion of Kapton. A self passivating, self healing silica layer protecting underlying Kapton upon exposure to AO may result from the nanodispersion of silicon and oxygen within the polymer matrix. Polyhedral oligomeric silsesquioxane (POSS) is composed of an inorganic cage structure with a 2:3 Si:O ratio surrounded by tailorable organic groups and is a possible delivery system for nanodispersed silica. A POSS dianiline was copolymerized with pyromellitic dianhydride and 4,4΄-oxydianiline resulting in POSS Kapton Polyimide. The glass transition temperature (Tg) of 5 to 25 weight % POSS Polyimide was determined to be slightly lower, 5 - 10 %, than that of unmodified polyimides (414 C). Furthermore the room temperature modulus of polyimide is unaffected by POSS, and the modulus at temperatures greater than the Tg of the polyimide is doubled by the incorporation of 20 wt % POSS. To simulate LEO conditions, POSS PI films underwent exposure to a hyperthermal O-atom beam. Surface analysis of exposed and unexposed films conducted with X-ray photoelectron spectroscopy, atomic force microscopy, and surface profilometry support the formation of a SiO2 self healing passivation layer upon AO exposure. This is exemplified by erosion rates of 10 and 20 weight % POSS PI samples which were 3.7 and 0.98 percent, respectively, of the erosion rate for Kapton H at a fluence of 8.5 x 1020 O atoms/sq cm.

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Document Details

Document Type
Technical Report
Publication Date
Nov 01, 2004
Accession Number
ADA435770

Entities

People

  • Amy L. Brunsvold
  • Darrell Marchant
  • Diego Troya
  • Eitan Grossman
  • George C. Schatz
  • Irina Gouzman
  • Lipeng Sun
  • Sandra J. Tomczak
  • Steve Svejda
  • Timothy K. Minton

Organizations

  • Air Force Research Laboratory

Tags

Communities of Interest

  • Energy and Power Technologies

DTIC Thesaurus Topics

  • Air Force
  • Air Force Research Laboratories
  • Charged Particles
  • Chemistry
  • Copolymers
  • Earth Orbits
  • Films
  • Glass Transition Temperature
  • Low Earth Orbits
  • Materials
  • Molecular Dynamics
  • Self Assembled Monolayers
  • Spectroscopy
  • Trajectories
  • Transition Temperature
  • X Ray Photoelectron Spectroscopy
  • X Rays

Readers

  • Polymer Science and Engineering.
  • Polymer Science and Technology
  • Thin Film Deposition Science.

Technology Areas

  • Microelectronics
  • Microelectronics - Graphene
  • Space