Incorporation of silica nanoparticles and polyurethane into hybrid composites for increase of char residue

Abstract

Effect of different chain extenders, silica nanoparticle loading, and using sol–gel method on the thermal properties of polyurethane (PU) hybrid composites was investigated from the viewpoint of increase of char residue and decomposition temperature. Two different chain extenders were used for this purpose, and the PU products were modified with (3-aminopropyl) triethoxysilane to obtain PUI (ethoxysilane-terminated PU with pyromellitic dianhydride chain extender) and PUBD (ethoxysilane-terminated PU with butanediol chain extender), respectively. Fourier-transform infrared spectroscopy was used for confirmation of synthesis of PUI and PUBD. Thermogravimetric analysis showed that char residue and thermal degradation temperature of PU hybrid composites were increased after incorporation of silica nanoparticles. Also, using pyromellitic dianhydride as chain extender resulted in higher char contents and also thermal stabilities in comparison with butanediol. By the addition of 4 and 8 mass% silica nanoparticles in PUBD hybrids, char residue increased to 15.1 and 16.3%, respectively. In the case of PUI hybrids, addition of 4 and 8 mass% of silica nanoparticles resulted in char residue of 20.8 and 25.7% and Tmax of 409.3 and 411.8 °C, respectively. X-ray diffraction showed an amorphous peak for cross-linked PU at 2θ = 21.7°. Transmission electron microscopy showed dispersion of silica nanoparticles in the hybrid composite of PUI.