Octasilsesquioxane-reinforced TMBP epoxy nanocomposites: Characterization of thermal,flame-retardant,and morphological properties

Organic–inorganic nanocomposites comprising epoxy resins and polyhedral oligomeric silsesquioxanes (POSS) were prepared via in situ polymerization of 3,3′,5,5′-tetramethyl-4,4′-biphenyl diglycidyl epoxy resins and 4,4′-diaminodiphenylsulfone. The thermal, fire-retardant, and morphological properties of the nanocomposites were studied using thermogravimetric analysis (TGA), thermogravimetry-Fourier transform infrared (TG-FTIR) spectroscopy, microscale combustion calorimeter (MCC), limiting oxygen index (LOI), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The peak heat release rate and the total heat release were significantly reduced with the incorporation of POSS into the epoxy networks, based on the MCC results. Moreover, the LOI value slightly increased with the increase in POSS content. Further, SEM and XPS were used to explore the char residues of the pure epoxy resin and POSS-containing system. The introduction of POSS was found to lead to the formation of an inert layer on the surface of the materials, which protects the internal structure from decomposition.