Protection of Polymers from the Space Environment by Atomic Layer Deposition

Abstract

Polymers in space may be subjected to a barrage of incident atoms, photons, and/or ions. For example, oxygen atoms can etch and oxidize these materials. Photons may act either alone or in combination with oxygen atoms to degrade polymers and paints and thus limit their usefulness. Colors fade under the intense vacuum ultraviolet (VUV) solar radiation. Ions can lead to the build‐up of static charge on polymers. Atomic layer deposition (ALD) techniques can provide coatings that could mitigate many challenges for polymers in space. ALD is a gas‐phase technique based on two sequential, self‐limiting surface reactions, and it can deposit very uniform, conformal, and pinhole‐free films with atomic layer control. We have studied the efficacy of various ALD coatings to protect Kapton® polyimide, FEP Teflon®, and poly(methyl methacrylate) films from atomic‐oxygen and VUV attack. Atomic‐oxygen and VUV studies were conducted with the use of a laser‐breakdown source for hyperthermal O atoms and a D2 lamp as a source of VUV light. These studies used a quartz crystal microbalance (QCM) to monitor mass loss in situ, as well as surface profilometry and scanning electron microscopy to study the surface recession and morphology changes ex situ. Al2O3 ALD coatings applied to polyimide and FEP Teflon® films protected the underlying substrates from O‐atom attack, and ZnO coatings protected the poly(methyl methacrylate) substrate from VUV‐induced damage.