Fire resistance of Scots pine modified with sorbitol, citric acid and fire retardants

Abstract

Sorbitol-citric acid (SorCA) modification is an eco-friendly wood treatment that demonstrates promising potential for enhancing dimensional stability and decay resistance of wood material. To improve the fire resistance property of SorCA (1:2; 30%) modified wood, fire retardants (FRs) such as diammonium hydrogen phosphate (DAP) and potassium carbonate (PC) were incorporated into the modification system at a rate of 10% and 15%, respectively. Scots pine wood modified with the combination of SorCA and FRs was subjected to mass loss calorimeter test to evaluate its flame retardancy. In addition, thermogravimetric analysis (TGA) was carried out for determining the thermal behaviour of modified wood at elevated temperatures. Fourier-transform infrared spectroscopy (FTIR) was used to identify the chemical bonds in the modified wood. The FTIR spectrum indicated an intensity enhancement at 1716 cm- 1, resulting from the bonding with the cell wall or between the reagents. TGA analysis showed that the addition of DAP and PC to the SorCA system enhanced the thermal stability, yielding higher residual mass compared to SorCA alone and the untreated reference. The mass loss calorimeter revealed that SorCA with DAP 15% significantly improved flame retardancy, lowering the peak heat release rate by 65% and total heat release within 600 s by 82% compared to untreated wood. The combination of SorCA with DAP and PC contributed to the char formation and showed potential flame retardancy for modified Scots pine wood.