Abstract
In this work, a thermal degradation mechanism of room temperature vulcanized (RTV) phenyl silicone rubber that was vulcanized by different crosslinking agents was discussed. Firstly, RTV phenyl silicone rubber samples were prepared by curing hydroxyl-terminated polymethyldiphenylsiloxane via three crosslinking agents, namely, tetraethoxysilane (TEOS), tetrapropoxysilane (TPOS), and polysilazane. Secondly, the ablation properties of RTV phenyl silicone rubber were studied by the muffle roaster test and FT-IR. Thirdly, thermal stability of the three samples was studied by thermogravimetric (TG) analysis. Finally, to explore the thermal degradation mechanism, the RTV phenyl silicone rubber vulcanized by different crosslinking agents were characterized by TG analysis-mass spectrum (TG-MS) and pyrolysis gas chromatogram-mass spectrum (pyGC-MS). Results showed that the thermal stability of RTV phenyl silicone rubber is related to the amount of residual Si–OH groups. The residual Si–OH groups initiated the polysiloxane chain degradation via an ‘unzipping’ mechanism.
Highlights
Silicone is the compound of Si atoms connected with organic groups through chemical bonds [1].It is more thermally stable than other organic compounds, resulting from the many chemical bonds containing Si atoms that have a higher bond energy, such as the Si–O bond, the Si–C bond, or theSi–N bond
The muffle roaster shows that room temperature vulcanized (RTV) phenyl silicone rubber vulcanized by polysilazane has a better thermal stability than RTV phenyl silicone rubber vulcanized by TEOS and TPOS
TG analysis showed that the RTV phenyl silicone rubber vulcanized by polysilazane has the optimum thermal stability, and the thermal pyrolysis reaction could be divided into two stages
Summary
Silicone is the compound of Si atoms connected with organic groups through chemical bonds [1].It is more thermally stable than other organic compounds, resulting from the many chemical bonds containing Si atoms that have a higher bond energy, such as the Si–O bond, the Si–C bond, or theSi–N bond. Silicone is the compound of Si atoms connected with organic groups through chemical bonds [1]. RTV silicone rubber is more flexible, easier to be vulcanized, and has a lower glass transition temperature than other silicone compounds. It has been extensively used as a polymer matrix of thermal protection systems (TPSs) in the field of aerospace, given its excellent thermal stability, favorable flexibility, and better low temperature resistance [2,3,4,5,6,7,8]. The Martin company utilized silicone rubber as the polymer matrix of the TPS of the Mars probe (SLA-561) [4]
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