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Antiadhesion elastomer seal coatings for UV and atomic oxygen protection
Author(s) -
de Groh Henry C.,
Puleo Bernadette J.,
Waters Deborah L.,
Miller Sharon K.
Publication year - 2015
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.41662
Subject(s) - materials science , elastomer , ultraviolet , composite material , atomic oxygen , oxygen , chemistry , optoelectronics , organic chemistry
ABSTRACT Radiation blocking sunscreen coatings have been developed for the protection of elastomer seals used in low‐Earth‐orbit (LEO). The coatings protect the seals from ultraviolet (UV) radiation and atomic oxygen (AO) damage. The coatings were developed for use on NASA docking seals. Docking seal damage from the UV and AO present in LEO can constrain mission time‐line, flight mode options, and increases risk. A low level of adhesion is also required for docking seals so undocking push‐off forces can be low. The coatings presented also mitigate this unwanted adhesion. Greases with low collected volatile condensable materials (CVCM) and low total mass loss (TML) were mixed with slippery and/or UV blocking powders to create the protective coatings. Coatings were applied at rates up to 2 mg/cm 2 . Coated seals were exposed to AO and UV in the NUV (near‐UV) and UV‐C wavelength ranges (300 to 400 nm and 254 nm, respectively). Ground based ashers were used to simulate the AO of space. The Sun's UV energy was mimicked assuming a nose forward flight mode, resulting in an exposure rate of 2.5 MJ/m 2 day. Exposures between 0 and 147 MJ/m 2 (UV‐C) and 245 MJ/m 2 (NUV) were accomplished. The protective coatings were durable, providing protection from UV after a simulated docking and undocking cycle. The level of protection begins to decline at coverage rates less than 0.9 mg/cm 2 . The leakage of seals coated with Braycote + 20%Z‐cote ZnO sunscreen increased by a factor of 40 after moderate AO exposure; indicating that this coating might not be suitable due to AO intolerance. Seals coated with DC‐7–16.4%Z‐cote ZnO sunscreen were not significantly affected by combined doses of 2 × 10 21 atoms/cm 2 AO with 73 MJ/m 2 UV‐C. Unprotected seals were significantly damaged at UV‐C exposures of 0.3 MJ/m 2 and DC‐7–16.4%Z‐cote coated seals were undamaged at all exposures up to the limits tested thus far which were 147 MJ/m 2 UV‐C and 245 MJ/m 2 NUV. The coatings decreased adhesion sufficiently for docking seals at temperatures equal to or greater than −8°C thus offer a simple and inexpensive way to mitigate adhesion. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132 , 41662.