Environmental Durability of Silver Teflon FEP Thermal Control Tape Protected by a SiO2/NiCr Backcoat
Session
Poster Session 4
Location
Salt Palace Convention Center, Salt Lake City, UT
Abstract
Silver Teflon® FEP thermal control tapes are widely used on small satellites due to their low solar absorptance and high infrared emittance. However, long-term operation in low Earth orbit (LEO) is often limited by degradation mechanisms associated with atomic oxygen (AO), ultraviolet (UV) radiation, and thermal cycling. In particular, silver–adhesive interactions and defect-mediated undercutting have been identified, based on results from NASA’s Long Duration Exposure Facility (LDEF) mission (5.7 years in LEO), as primary contributors to the increase in solar absorptance over mission life. This work investigates a SiO2/NiCr protective backcoat film stack sputtered on top of the silver layer in Silver Teflon® FEP tape. A thin NiCr metallic interlayer is deposited directly onto the silver to enhance adhesion, suppress silver diffusion, and mechanically support the oxide layer, followed by a SiO2 backcoat that serves as an AO-resistant and chemically inert diffusion barrier. A 10-mil Silver Teflon® FEP tape with the backcoat was exposed to a simulated AO environment in a radio-frequency (RF) plasma asher to a Kapton-equivalent effective fluence of approximately 1.30 ⋅ 1021 atoms/cm2. Total solar reflectance was evaluated per ASTM E903 from spectral reflectance measured over 250 to 2500 nm and weighted by the AM0 solar spectrum. The FEP front surface exhibited a modest decrease in total solar reflectance of approximately 6.8%. The measured AO erosion yield of the front FEP was consistent, on a depth-recession basis, with established flight values for Teflon FEP from past MISSE and LDEF missions, while the SiO2/NiCr backside surface remained essentially unchanged. These results indicate that the protective backcoat retains stable thermo-optical performance, with degradation governed by the well characterized erosion of the bare FEP front surface rather than by the protective backcoat. The film stack offers a robust and manufacturable alternative to the Inconel backcoats that have been the industry standard for the past four decades, is compatible with roll-to-roll magnetron sputtering, and is well suited for typical LEO applications where a controlled increase of end-of-life (EOL) solar absorptance is required.
Document Type
Event
Environmental Durability of Silver Teflon FEP Thermal Control Tape Protected by a SiO2/NiCr Backcoat
Salt Palace Convention Center, Salt Lake City, UT
Silver Teflon® FEP thermal control tapes are widely used on small satellites due to their low solar absorptance and high infrared emittance. However, long-term operation in low Earth orbit (LEO) is often limited by degradation mechanisms associated with atomic oxygen (AO), ultraviolet (UV) radiation, and thermal cycling. In particular, silver–adhesive interactions and defect-mediated undercutting have been identified, based on results from NASA’s Long Duration Exposure Facility (LDEF) mission (5.7 years in LEO), as primary contributors to the increase in solar absorptance over mission life. This work investigates a SiO2/NiCr protective backcoat film stack sputtered on top of the silver layer in Silver Teflon® FEP tape. A thin NiCr metallic interlayer is deposited directly onto the silver to enhance adhesion, suppress silver diffusion, and mechanically support the oxide layer, followed by a SiO2 backcoat that serves as an AO-resistant and chemically inert diffusion barrier. A 10-mil Silver Teflon® FEP tape with the backcoat was exposed to a simulated AO environment in a radio-frequency (RF) plasma asher to a Kapton-equivalent effective fluence of approximately 1.30 ⋅ 1021 atoms/cm2. Total solar reflectance was evaluated per ASTM E903 from spectral reflectance measured over 250 to 2500 nm and weighted by the AM0 solar spectrum. The FEP front surface exhibited a modest decrease in total solar reflectance of approximately 6.8%. The measured AO erosion yield of the front FEP was consistent, on a depth-recession basis, with established flight values for Teflon FEP from past MISSE and LDEF missions, while the SiO2/NiCr backside surface remained essentially unchanged. These results indicate that the protective backcoat retains stable thermo-optical performance, with degradation governed by the well characterized erosion of the bare FEP front surface rather than by the protective backcoat. The film stack offers a robust and manufacturable alternative to the Inconel backcoats that have been the industry standard for the past four decades, is compatible with roll-to-roll magnetron sputtering, and is well suited for typical LEO applications where a controlled increase of end-of-life (EOL) solar absorptance is required.
