Fire retardancy impact of sodium bicarbonate on ligno-cellulosic materials

In this paper, the effect of NaHCO3 as fire retardant additive during pyrolysis and combustion has been investigated. Four different contents (5%, 10%, 15%, and 20% w/w) of NaHCO3 have been tested on Pinus brutia, Laurus nobilis and Nerium oleander; forest species commonly dispersed in the Mediterranean region. Pyrolysis experiments have been conducted using a thermogravimetric analyzer (TGA) employing nitrogen (N2) flow of 50 ml/min, under a heating rate of 10 °C/min. Experiments for flaming combustion have been conducted in a specially designed furnace, isothermally controlled, under an air flow supply of 1.5 l min−1; key parameters including time to self ignition and duration of flame combustion were measured. Pyrolysis data revealed that the addition of NaHCO3 induces a shift towards lower thermal degradation temperatures for each of the forest specie considered. Thus, sodium bicarbonate decreases the threshold of initial temperature of pyrolysis of forest species (promotion effect). On the other hand NaHCO3 increases the self ignition delay time and combustion duration of forest species (inhibition effect). In addition the presence of NaHCO3 increases the pyrolysis mass residue of forest species, especially when sodium carbonate applied on N. oleander.