Evaluation of the abilities of atomic oxygen/ultraviolet resistance for the filled silicone rubber coating: Structures, properties, and aging mechanism

A series of experimental techniques were used to study the erosion-damage effect of a silica-filled silicone rubber coating exposed to simulated space environment (atomic oxygen and ultraviolet irradiation). The elastomer is known to be chemically and thermally stable, but there are insufficient data on its durability in the space environment. In the present work, atomic oxygen doses up to 3.8 × 1021 atoms·cm−2 and ultraviolet irradiation doses up to 360 equivalent sun-hours (ESH) were applied from Space Environment Simulation Measurement System, respectively. Since the aging and failure processes of the filled silicone rubber relate to different aspects of chemical structure and physics form, therefore, this study explored the use of chemical-mechanics methods to comprehensively evaluate the erosion-damage effect of materials. Morphology and chemical changes due to radiation were investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), and nanoindentation test probed surface mechanical properties changed with exposure dose. Results demonstrated that, with increased exposure time and irradiation-induced free radicals，the aggregation state and molecular chain structure of the silica-filled silicone rubber have changed, which caused an increase in surface hardness and modulus. Taken together, the results indicated that oxidative cross-linking was the dominant degradation mechanism under the irradiation dose in this paper.