Liquid Phase Deposition of a Space-Durable, Antistatic SnO₂ Coating on Kapton

Abstract

Polyimides are widely used in thermal blankets covering the external surfaces of spacecrafts due to their space durability and their thermo-optical properties. However, they are susceptible to atomic oxygen (AO) erosion, the main hazard of low Earth orbit (LEO), and to electrical charging. This work demonstrates that liquid phase deposition (LPD) of 100 nm of tin oxide creates a protective coating on Kapton polyimide that has good adherence and is effective in preventing AO-induced surface erosion and in reducing electrical charging. The as-deposited tin oxide induces no significant changes in the original thermo-optical properties of the polymer and is effective in preventing electrostatic discharge (ESD). The durability of the oxide coating under AO attack was studied using oxygen RF plasma. The AO exposure did not result in any significant changes in surface morphology, thermo-optical, mechanical, and electrical properties of the tin oxide-coated Kapton. The erosion yield of tin oxide-coated Kapton was negligible after exposure to 6.4 × 10(20) O atoms·cm(-2) of LEO equivalent AO fluence, indicating a complete protection of Kapton by the LPD deposited coating. Moreover, the tin oxide coating is flexible enough so that its electrical conductivity stays within the desired range of antistatic materials despite mechanical manipulations. The advantages of liquid phase deposited oxides in terms of their not being line of site limited are well established. We now extend these advantages to coatings that reduce electrostatic discharge while still providing a high level of protection from AO erosion.

Advances in Polyimide‐Based Materials for Space Applications

“…For example, indium tin oxide (ITO) is used in applications where electrostatic discharge (ESD) protection is essential . We have applied TiO 2 and SnO 2 coatings on Kapton films by the liquid phase deposition (LPD) process . Minton et al studied the efficacy of atomic layer deposited (ALD) Al 2 O 3 and TiO 2 coatings in protecting Kapton H, FEP Teflon, and poly(methyl methacrylate) (PMMA) films from AO and VUV attack.…”

Polyhedral oligomeric silsesquioxane polyimide nanocomposites for color filters and flexible conductive films

“…Traditional conductive coatings, such as metals and indium tin oxides, are sputtered or deposited as thin films onto flexible substrates such as polyimide for spacecraft applications 28–33 . Conductive metals such as copper, silver, and aluminum are used in spacecrafts, and their conductivity degrades when exposed to AO in LEO 34,35 .…”

Hyperthermal atomic oxygen durable transparent silicon-reinforced polyimide

“…Table 1 lists AO test conditions and erosion data of various materials based on polyimide in previous studies, mainly including inorganic coatings and reinforcement of silicon (Si) element. [24][25][26]27,28, Inorganic coatings on polyimide surfaces, such as silicon dioxide (SiO 2 ), metal oxide, and metal coatings, help spacecrafts resist the harsh oxidative LEO environment. [24][25][26][36][37][38][39][40] However, metal coatings of silver and copper are easy to get oxidized.…”