The optimum level of nano-wollastonite consumption as fire-retardant in poplar wood (Populus nigra)

Fire-retarding properties of wollastonite nanofibers in poplar wood (Populus nigra) were studied here. Some physical properties such as water absorption, volumetric swelling and anti-swelling efficiency (ASE) were also measured. Specimens were prepared according to the ISO 11925 specifications for the fire-retarding properties and according to the ASTM D4446 -2002 specifications for the physical properties. Impregnation of wood specimens with nanowollastonite was carried out at consumption levels of 4, 6.3, 10 and 12%, using Rueping Method (empty-cell process) and compared with the control specimens. Five fire-retarding properties were measured, including weight loss (%), ignition point (s), fire endurance (s), glow endurance (s) and carbonization area (%). The obtained results indicated that fire-retarding properties were significantly improved in the NW-treated specimens. Furthermore, the NW-impregnated specimens gained higher dimensional stability. However, water absorption increased. Heat-conductivity of wollastonite limited accumulation of heat at one spot, furthermore, it acted as a physical barrier to deter heat and mass transfer between the gas and the condensed phase, consequently, fire-retarding properties were improved.