Relationship between structure and thermal stability of fluorosilicones at high temperatures

• Anisothermal and isothermal degradation of fluorosilicone based rubbers studied by TGA. • Comparison of homo-, co-, terpolymers, uncrosslinked and crosslinked, filled and unfilled materials. • Improvement of thermal stability by fillers and crosslinking. • Discussion of chemical mechanisms (depolymerization, scission of lateral chains). The thermal stability of fluorosilicones at high temperatures has been investigated with thermogravimetric analysis (TGA) based on their chemical structure (copolymerization and crosslinking), and compounding (incorporation of silica and titanium dioxide particle fillers). This allowed the comparison of thermal degradation kinetics of model samples and commercial fluorosilicones rubbers. Increasing dimethylsiloxane content in copolymers enhances thermal stability, while the presence of vinyl groups accelerates degradation by promoting depolymerization and crosslinking reactions at an earlier stage. In model filled fluorosilicone rubbers (FSR), untreated silica particles were found to destabilize the polymer matrix in the short term, whereas commercial filled FSRs exhibited greater thermal stability due to treated silica surfaces. Additionally, commercial samples crosslinked with DCP mixed with CaCO 3 resulted in the highest thermal stability. FTIR transmission analysis of copolymer residues revealed that degradation does not favor the preferential release of any monomer (dimethylsiloxane or trifluoropropylmethylsiloxane). Elemental analysis of a model homopolymer suggested that depolymerization is the dominant degradation mechanism, but side group scissions also contribute to this process.