S. H. Jiang, B. Yu, K. Q. Zhou, H. Y. Yang, Y. Q. Shi, S. M. Lo, Y. Hu and Z. Gui (2014) Sol-gel synthesis and enhanced properties of a novel transparent PMMA based organic-inorganic hybrid containing phosphorus, nitrogen and silicon. Journal/Journal Of Sol-Gel Science And Technology 69 418-428. [In English]
Web link: http://dx.doi.org/10.1007/s10971-013-3236-x
Keywords: ,Poly(methyl methacrylate), Sol-gel method, Organic-inorganic hybrids, Flame retardancy, Thermal property, Mechanism, INTUMESCENT FLAME-RETARDANT, POLY(METHYL METHACRYLATE), THERMAL-PROPERTIES, SURFACE MODIFICATION, FIRE RETARDANCY, NANOCOMPOSITES, DEGRADATION, COPOLYMER, MONTMORILLONITE, NANOPARTICLES

Abstract: A novel flame-retardant silane containing phosphorus and nitrogen, tetramethyl(3-(triethoxysilyl)propylazanediyl) bis(methylene) diphosphonate (TMSAP), is firstly synthesized and then incorporated into poly(methyl methacrylate) (PMMA) matrix through sol-gel method to produce organic-inorganic hybrids. The chemical structure of TMSAP was confirmed by Fourier transform infrared spectra, H-1 nuclear magnetic resonance (NMR) and P-31 NMR spectra. The hybrids obtained maintain relatively high transparency, and exhibit a significant improvement in thermal properties, mechanical performance and flame retardancy when compared to pure PMMA, including increased glass transition temperature (T (g) ) by 11.4 A degrees C, increased onset thermal degradation temperature (T-0.1) by 82.6 A degrees C, increased half thermal degradation temperature (T-0.5) by 42.0 A degrees C, increased hardness, increased limited oxygen index and decreased heat release rate. Morphological studies of hybrids by scanning electron microscopy (SEM) and Si-29 MAS NMR suggest that cross-linked silica network is formed in the hybrids and the inorganic silica particles are distributed well in the polymer matrix. Thermal degradation behaviors investigated by thermogravimetric analysis and char structure analysis studied by SEM and X-ray photoelectron spectroscopy demonstrate the catalytic charring function of TMSAP, and synergistic effect between phosphorus, nitrogen and silicon element. The formation of network structure, homogeneous distribution of silica and the char formation during degradation play key roles in these property enhancements. Detailed mechanisms for these enhancements are proposed.