SBIR-STTR Award

Polymers and paints in space are subjected to a barrage of incident oxygen atoms, UV and VUV photons and ions. The oxygen atoms and photons can erode the polymer and the ions can lead to the buildup of static charge. This Phase I proposal will use atomic layer deposition (ALD) methods to coat polymers with various conformal films to protect the polymer and prevent the buildup of static charge. Al2O3 ALD will be used to prevent oxygen atom corrosion of Teflon polymers. TiO2 ALD and ZnO ALD will be employed to absorb UV and VUV photons to prevent photodegradation of PMMA polymers. ZnO ALD and possibly TiO2 ALD will be used to provide electrical conductivity to remove static charge on Kapton or Teflon polymers. Earlier work by this research team has demonstrated that Al2O3 ALD films with a thickness of ~35 Å can completely protect Pyralin polymer films from erosion by hyperthermal oxygen atoms. The proposed Phase I work will build on these earlier investigations and extend the ALD method to other polymers and to the problems of UV and VUV erosion and the buildup of static charge.

Keywords:
Polymers, Atomic Layer Deposition, Protective Coatings, Oxygen Atom Corrosion, Photodegradation, Static Charge Buildup

Polymers in space are subjected to various threats including hyperthermal oxygen atoms, UV and VUV photons, and ions.  These threats can degrade the polymer and lead to static charge accumulation.  This Phase II proposal will build on the Phase I work which demonstrated that inorganic films grown by atomic layer deposition (ALD) can protect polymers such as Kapton, Teflon and PMMA.  Al2O3 ALD films can prevent oxygen atom corrosion.  TiO2 ALD can be employed to absorb UV/VUV radiation.  ZnO ALD can be used to dissipate static charge. The Phase II work will explore the mechanisms of polymer degradation by atomic oxygen and VUV radiation.  The new work will also examine the cracking of inorganic films on polymers resulting from different thermal expansion coefficients as well as develop new multilayer films that should display increased strength and flexibility.  Phase II will explore coatings to enhance the durability of POSS copolymers as well as commercially important polycarbonates and acrylics that are used on aircraft window and canopies.  ALD-coated polymeric films will be tested in low Earth orbit on the International Space Station.  The ALD process will be scaled up to perform validation testing with our commercial partners in the aerospace industry.

Benefit:
Degradation of polymers in the space environment limits the lifetime of commercial and military space vehicles.  Polymers used in thermal control systems and energy harvesting panels erode because of hyperthermal oxygen atoms and VUV and UV radiation.  In addition, windows and canopies on commercial and military aircraft have to be replaced frequently due to weathering.  Current coatings cannot withstand the mechanical and thermal stresses nor protect against oxygen atoms and radiation.  Conventional line-of-sight deposition methods can also not easily coat 3D objects.  Atomic layer deposition (ALD) coatings have demonstrated protection against oxygen atom and VUV photodegradation during the Phase I work.  The proposed Phase II work will validate multilayer ALD protective coatings for polymers in low Earth orbit and establish commercial viability for the aerospace industry.  These results, together with additional understanding of the polymer degradation mechanisms, will lead to commercial applications for these ALD coatings on polymers.  One example is transparent, durable, UV blocking and flexible coatings for acrylics and polycarbonates use as aircraft windows and canopies.  In addition to the space vehicle and aircraft applications, these protective coatings will also be useful in other consumer applications such as flexible organic light emitting diodes (OLEDs) for flexible displays on polymer substrates.

Keywords:
Polymers, Atomic Layer Deposition, Protective Coatings, Oxygen Atom Corrosion, Photodegradation, Sta