NASA developed Protective Ceramic Coatings (PCC) for the X-33; NASA's re-usable Space Vehicle Program. Wessex Incorporated was able to license the patent for PCC for the purpose of its commercialization into unique products for the ceramic, refractory, metal textile and other markets.
The NASA developed PCC, and therefore Emisshield Products, is based upon the important concept of emissivity for substrate protection and increased performance. Emissivity is defined as a substrates ability to absorb energy and subsequently re-radiate that energy to a cooler place.
Any substrate: metal, ceramic, refractory, paint, wood, etc., has an emissivity rating between 0.0 and 1.0. However, most of these emissivity ratings are based upon ambient temperatures. When temperatures increase most substrates are destroyed or see their emissivity reduce significantly. If a substrate has an emissivity of 0.01, it would not absorb and therefore release energy as well as a substrate with an emissivity if 0.98. The graph below demonstrates this with three different types of metal versus steel coated with an Emisshield Coating.
Where: qre-rad. is measured in units of Btu/hour-ft
s = Stefan-Boltzmann Constant
Ts = surface temperature
Tsur= surrounding temperature
This formula shows that emissivity is a function of temperature in that as the temperatures rise, the reradiation potential increases. Emisshield Coatings have a high emissivity rating of 0.8 to 0.9 at low and high temperatures.
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