Preparation and thermal stability of poly(methyl methacrylate)/rice husk silica/triphenylphosphine nanocomposites: assessment of degradation mechanism using model-free kinetics

Abstract

Nanostructured silica powder was prepared from rice husk ( Oryza sativa), an outer covering of rice. Silica was characterized using Fourier transform infrared spectroscopy, X-ray diffraction and transmission electron microscopy. The silica powder thus prepared was treated with stearic acid for the surface modification. The modified silica was utilized to prepare poly(methyl methacrylate)/modified silica composite films at 1, 5 and 10 wt% loadings by solution casting method, which promises the preparation of homogeneous composites. For comparative analyses, composite films were also made using unmodified silica. Distribution of silica particles in composite film was checked using scanning electron microscopy. Thermal analysis of the samples was carried out using thermogravimetric analyzer followed by model–free multiple–heating rate kinetics. The onset degradation temperature of poly(methyl methacrylate)/silica (modified) composites is found higher than both pure poly(methyl methacrylate) and corresponding poly(methyl methacrylate)/silica (unmodified) composites. This study also reveals the effect of a phosphorus flame retardant additive, triphenylphosphine, on the thermal degradation and flammability behavior of poly(methyl methacrylate) and poly(methyl methacrylate)/silica (modified).