MECHANISMS OF DEGRADATION OF POLYMERIC THERMAL CONTROL COATINGS. PART I. INVESTIGATION ON DEGRADATION OF THERMAL CONTROL COATING MATERIALS
Technical rept. 1 Jun 1967-3 Sep 1968
GULF GENERAL ATOMIC CO SAN DIEGO CA
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Progress of an investigation on the mechanisms of degradation of white pigments used in polymeric thermal control coatings by ultraviolet radiation is reported. The materials investigated were rutile TiO2 with different controlled impurity levels and surface treatments and high-purity strontium titanate SrTiO3. Apparatus combining a gas chromatograph with means for measuring optical reflectance and electrical conductivity enables samples of pigments to be investigated in a controlled environment. Changes in optical properties, produced by exposure to ultraviolet light, are correlated with gas evolution and adsorption. Some optical changes were correlated with gas evolution and electrical conductivity. The gas evolved in all cases was CO2, with no O2 being observed. Carbonaceous impurities found in these materials are believed to play a role in the damage process. Instrumentation and test techniques were developed, including a recently completed reflectometer of novel design. A comparison was made between chemical reduction of various rutile pigments and the effects of uv light Chemical reduction produces changes in optical and other properties that correlate with one of the two types of effects produced by uv light reduction of reflectance near one micron and the relative susceptibility of different pigments to chemical reductions similar to their relative susceptibility to uv degradation.
- Radiation and Nuclear Chemistry
- Coatings, Colorants and Finishes