Effect of Combined Fire- and Bio-Protective Coatings on the Thermal Degradation of Spruce Wood: Insights from Radiant Heat and Simultaneous Thermal Analysis
Keywords:
Boron-based coating, Fire-retardant coating, HR Prof, Krovsan, Mass loss, Norway spruce, Radiant heat exposure, Wood thermal degradation, Simultaneous thermal analysis (STA)Abstract
The influence of two commercial fire-retardant formulations, HR Prof and Krovsan, and their mixtures on the thermal behavior and fire resistance of spruce wood was evaluated by simultaneous thermal analysis STA (namely TG/DTG/DSC) and radiant-heat exposure. The untreated wood exhibited the typical three-stage degradation of lignocellulosic material with a maximum mass-loss rate near 265 °C. All treated specimens showed delayed decomposition, reduced oxidation rate, and markedly higher residual mass at 700 °C. A strong correlation was found between thermogravimetric residue and the mass retained after radiant-heat testing, confirming that improved performance resulted from condensed-phase stabilization. Phosphorus–nitrogen components of HR Prof promoted early dehydration and intumescence, while boron–copper species in Krovsan reinforced the carbonized layer and limited oxidation at elevated temperature. The balanced mixture (50 HR – 50 KR) provided the most effective protection, combining early char formation with long-term stability. The synergistic action of HR Prof and Krovsan thus offers an efficient and environmentally acceptable strategy for enhancing the fire safety of spruce wood.
