Influence of nano-silica on flame resistance behavior of intumescent flame retardant cellulosic textiles: Remarkable synergistic effect?

• Intumescent flame retardant (APP/PER/MEL) cotton fabric treated by nano-silica
• Comparisons between APP/PER/MEL without and with nano-silica using TG, FTIR, MCC, LOI and VBT tests
• Appropriate amount of nano-silica improve flame retard properties of IFR cotton fabric.
• IFR coating cotton fabric with nano-silica worsened thermal stability.

In recent years, nano-silica has emerged as a promising synergistic agent for improving the flame retardancy of intumescent flame retardant (IFR) polymer materials. However, few researches have been focused on the influence of the nano-silica on the flame retardant behavior of IFR cellulosic materials. In the paper, flame retardant mixtures of nano-silica and traditional IFR (NS-IFR) were applied on cotton fabric (CF) to investigate the synergistic effect of nano-silica on the thermal stability and fire resistance of IFR system. The results of the limited oxygen index (LOI) test and the vertical burning test (VBT) demonstrated that the flame retardancy of the treated cotton fabric was optimized when 4 wt% APP/PER/MEL was replaced by the 4% nano-silica. But it is impaired with increasing the concentration of nano-silica. Char residues, characteristic decomposition temperatures and heat release data from thermogravimetric (TG) and micro-scale combustion calorimeter (MCC) measurements revealed that appropriate addition of nano-silica into traditional IFR system can improve the fire protection properties of IFR-CF to a certain extent, but cause depress in thermal stability of IFR-CF. Therefore, for cellulosic textiles, it is not strongly recommended for use of nano-silica as synergistic agents in IFR system.