Electron, Proton, and Ultraviolet Radiation Effects on Thermophysical Properties of Polymeric Films

Abstract

The response of coated thin polymer films to simultaneous ultraviolet, electron, and proton radiation has been evaluated by selected measurements in situ and in the laboratory. Exposures simulated the radiation environment near the Earth-sun Lagrangian points 1 and 2 for five years and ∼1000 ultraviolet equivalent solar hours. Materials evaluated were both commercially available and newly developed aromatic polyimide films aluminized on one side and exposed as second surface mirrors. Effects on solar absorptance, thermal emittance, and tensile properties were measured. The in situ changes in solar absorptance of Kapton® and Upilex® were less than 0.1, whereas the solar absorptance of TOR and CP films increased by more than 0.3 without saturating. Thermal emittance measurements also showed that the Kapton and Upilex materials increased only 1-2%, but the remaining materials increased 5-8%. Tensile property measurements made in air following the test showed the failure stress of every type of polymer film decreased as a result of irradiation.