Combustion behavior of furfurylated wood in the presence of montmorillonite and its char characteristics

To investigate the combustion behavior of furfurylated wood in the presence of montmorillonite (MMT) and its char properties, original, MMT-treated, furfuryl alcohol (FA)-treated (i.e., furfurylated), and MMT/FA-treated wood were pyrolyzed and carbonized using thermo-gravimetry and cone calorimeter, respectively. Results on thermal stability, gas emission, microstructure, surface area, porosity, and chemical components confirmed that MMT dramatically affected the pyrolysis features of both control and furfurylated wood, and increased the char yield due to the catalytic activity and barrier effect of the clay sheets. Furfurylated wood released massive carbon-containing compounds and heat during combustion, which supported burning. The flame retardancy index (FRI) values of MMT/FA-treated wood were increased by 65.6% compared with the furfurylated wood, suggesting that MMT inhibited the spreading of gases and heat and promoted the formation of protective char layer. MMT uniformly distributed in wood cell lumina, promoted the effective carbonization of cellulose, and restrained the formation of carbon gaseous species, thus exerting a pronounced effect on char formation. The microstructure and chemical composition of the char residue indicated that due to the acid catalysis and barrier property of MMT sheets and the wrap of furfuryl alcohol resin, the coherent surface and porous structure of the char residues with Si–O–C/C–Si structures dominated the char-forming process, which was conducive to the comprehensive utilization of modified wood waste.