Greatly improving thermal stability of silicone resins by modification with POSS

Silicone resins, due to its excellent high thermal stability, are widely applied in high-temperature environment. However, it is still a problem that the initial decomposition temperature of silicone resins is relatively low, which limits their wider applications. In this paper, three kinds of polyhedral oligomeric silsesquioxane (POSS) (aminopropyl, mercaptopropyl and chloropropyl) were synthesized and analyzed by FTIR, NMR and MS for structure characterization and purity analysis. Significant improvement of thermal stability was achieved by incorporating POSS into silicone resins. Three different POSS were used to modify silicone resins, and the effects of different POSS on thermal stability of silicone resins were studied. The results indicated that the thermal stability of octa-aminopropyl POSS modified silicone resins improved most significantly, with the decomposition temperature increased by nearly 45 °C compared with pure silicone resins. Moreover, the thermal decomposition mechanism of silicone resins with different POSS was studied, and chemical simulation indicated the thermal stability of silicone resins greatly improved by forming hydrogen bond between POSS and silicone resins. And the results showed one distinctive mode of increasing thermal stability, forming hydrogen bond to block resin chains' movements.