Reaction control and pyrolysis evolution of one-pot synthesized polysiloxane-resorcinol-terephthalaldehyde hybrid thermal insulation monoliths

Polysiloxane modified phenolic porous materials are useful as lightweight thermal insulators. This work proposed an efficient and controllable process to prepare polysiloxane-resorcinol-terephthalaldehyde (SiRT) hybrid porous monolith by one-pot synthesis from monomers and ambient pressure drying. 1 H NMR, FTIR and XPS results on molecular structure confirmed the hybrid networks were composed of crosslinked polysiloxane and phenolic with chemical linkage of Schiff base via reaction of γ-aminopropyl(diethoxy)methylsilane (APDEMS) with terephthalaldehyde. The reaction was crucial to promote transformation of terephthalaldehyde for achieving homogenous hybrid prepolymer solution in one-pot synthesis. The well controlled procedure resulted in formation of intact monoliths with average values of density of 0.273 g/cm 3 , compressive strength of 2.46 MPa, and room temperature thermal conductivity of 0.052 W/(m‧K). Under 1300 °C-pyrolysis, hybrid monoliths were transformed to lightweight thermally stable insulator. Pyrolysis mechanisms under major steps were revealed by Py-GC-MS results and structural analysis on pyrolyzed derivatives. Polysiloxane-resorcinol-terephthalaldehyde hybrid and the pyrolyzed porous monoliths are potential in the field of thermal insulation due to their good comprehensive performance.