Nitrocellulose-based hybrid materials with T7-POSS as a modifier: effective reinforcement for thermal stability, combustion safety, and mechanical properties

Abstract

Novel nitrocellulose (NC)-based hybrid materials with self-synthesized heptaphenyltricycloheptasiloxane trihydroxy silanol (T7-POSS) as a modifier were prepared using a “one-step” chemical cross-linking process. To comprehensively demonstrate the superiority of the modifier, hybrid materials with different contents of T7-POSS were assessed. The gel content was measured, and the chemical structure and composition of the T7-POSS-NC hybrid materials were characterized by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). Thermogravimetric analysis (TGA) results showed that the thermal stability of the T7-POSS-NC hybrid materials increased with the T7-POSS content. Typically, when 12.3 wt.% T7-POSS was incorporated into the NC, the decomposition temperature based on 50% weight loss (T50%) was delayed from 183.3 °C to 243.5 °C, the maximum weight loss rate (WLRmax) decreased markedly from 432.9%/min to 1.3%/min, and the char residues increased from 1.4% to 26.0%. The scanning electron microscopy (SEM) results of the char residues indicated that the introduction of T7-POSS led to the formation of a sufficient and compact char layer. Notably, the incorporation of T7-POSS improved not only the combustion safety according to micro-scale combustion calorimeter (MCC) results but also the mechanical prop-erties due to the formation of cross-linking networks and the good distribution of T7-POSS particles, which was confirmed by SEM and energy-dispersive spectroscopy (EDS).