Relationship Between Photofixed, Effluent, and Bulk Composition of Several Room-Temperature-Vulcanized Materials

摘要

Raman spectroscopy and Fourier transform infrared spectroscopy are employed to analyze the bulk compositions of five kinds of room-temperature-vulcanized silicones (CV2568, RTV566, DC93-500, SCV2590, and SCV2590-2) that are commonly employed in orbiting spacecraft. It is found that polydimethylsiloxane, silicon dioxide, tetra-n-propylsilicate (NFS), silicic acid, tetraethyl orthosilicate, and trimethylsilanol are contained in all of them. The outgassing products from those silicones are characterized by Fourier transform infrared. By comparing the position of the peaks, it is found that the outgassing products of each material are polydimethylsiloxane and tetra-n-propylsilicate, which are consistent with the compositions of samples determined with Raman and Fourier transform infrared, respectively. These results indicate that the composition analysis of bulk or thin film silicones with Raman and Fourier transform infrared could be used as the guideline to predict the outgassing products of silicones. This, in turn, can lead to a more global approach for determining photofixing issues associated with outgassing. In support of this, the photofixed films from pure polydimethylsiloxane and tetra-n-propylsilicate, and their mixtures were analyzed by spectroscopic ellipsometry, and their optical constants were determined.