AZJ-4020 is a sprayable epoxy based thermal control coating that was originally developed for terrestrial applications. This coating was developed for the Haleakala high altitude observatory. AZJ-4020 has been exposed to atmospheric conditions at the observatory with little to no change to it’s optical properties.
This coating system has been proven to withstand the elements, in a particularly harsh environment. The starting solar absorptance was 0.145 and the thermal emittance was 0.930, the results after a full year of exposure were 0.145 solar absorptance and 0.940 thermal emittance.
In addition, all components of AZJ-4020 have spaceflight history. It has been flown on recent Materials International Space Station Experiment (MISSE) flights.
Rendering Courtesy of Tom Kekona, K.C. Environmental, Inc.
The March 2008 issue of the newsletter of the Advanced Technology Solar Telescope Project, reports that,
“The properties of traditional white coatings and paints are known to degrade with time as they are exposed to the elements. The thermal coating system for the ATST is based on test results of samples weathered on the Haleakalā High Altitude Observatories site. Two coatings have been identified for ATST…. The coating system for the most critical areas is AZJ-4020 white epoxy thermal-control coating manufactured by AZ Technology. Initial test results indicate a solar reflectance of just over 86% and near-normal emittance of 97% after one year of weathering.” ATST Quarterly News, Vol. 4, No. 1: March 2008. Reproduced couresy of NSO/AURA.
This quote from the ATST newsletter represents a brief summary of a larger ATST study comparing the impact of 1 year of weather exposure atop Haleakalā on the island of Maui, Hawaii on solar reflectance and near-normal emittance of a number of coatings from various manufacturers. The study is described in detail in the proceedings paper of L. Phelps from the National Solar Observatory,
Phelps, L. (2008) “Evaluation of thermal control coatings exposed to ambient weather
conditions at Haleakalā High Altitude Observatory,” Ground-based and Airborne Telescopes II, edited by Larry M. Stepp, Roberto Gilmozzi, Proc. of SPIE Vol. 7012, 701230, (2008)
The paper is available for a modest purchase price from SPIE.
The Advanced Technology Solar Telescope (ATST) Project is a large collaboration of segments of the solar physics community that is in the design phase to build the next-generation earth-based solar telescope.
AZJ-4020 represents an example of AZ Technology’s ability to develop customized thermal control and conductive paints/coatings for use in terrestrial applications.
|Nominal Surface Resistivity||N/A|
|Thermal Emittance (ε_t)||0.88 ± 0.02|
|Solar Absorptance (α_s)||0.15 ± 0.02 at ≥ 5.0 mils thickness|
|Use Temperature Range||-180 C to 200 C|
|Nominal Dry Thickness||~5.0 mils (over 85% of coated area)|
|ASTM D3359A Adhesion Grade||Not less than 3A|
|Full Cure||48-72 hours|