Burning and Thermal Degradation of Wood Under Defined Conditions: A Route of Preparation of Carbonaceous Char and Its Characterization for Potential Applicability in Evaluation of Real Fire

The burning process of wood types typically used in building construction (spruce) and for floor, furniture, and home accessories (oak and birch) using the specimen samples of the size 100 × 100 mm with a thickness of 8 mm was evaluated by a cone calorimeter and characterized by the time to ignition, the heat released, and the mass loss at several cone radiance. The carbonaceous char residues remaining after specified conditions of wood burning were characterized by an electron paramagnetic resonance spectroscopy and elemental analysis. Cone calorimeter tests revealed that time to ignition decreasing in order oak > birch > spruce and total time of burning is predominantly determined by the type of wood, initial mass, and depends on the cone radiance. According to maximum average rate of heat emission the cone calorimetry of respective woods shows the order of flammability as spruce < oak < birch. The comprehensive set of heat release rate data is of interest for fire modelling. By the EPR spectroscopy it was found that carbonaceous char residue involves qualitatively two different radical sites with slightly different g-factor values assigned to the aliphatic π-type radicals located on hydrocarbons and to the radicals of simple/complex aromatic hydrocarbons. Spin concentration elucidated from EPR spectra of chars revealed good correlation with the H atom content. An important practical output is aimed to characterization of char residue in real fires and thus more exact localization of the site of initial ignition.