Development of a pyrolysis model for oriented strand board. Part I: Kinetics and thermodynamics of the thermal decomposition

Oriented strand board is a widely used construction material responsible for a substantial portion of the fire load of many buildings. To accurately model the response of oriented strand board to fire, thermogravimetric analysis, differential scanning calorimetry, and microscale combustion calorimetry tests were carried out to construct a thermal decomposition model using a numerical solver, ThermaKin, and a hill climbing optimization algorithm. The model included a single-step water vaporization reaction and four consecutive reactions representing thermal decomposition of organic constituents of oriented strand board. The experiments and modeling revealed that the first two of the four reactions are endothermic, while the last two are exothermic. The net heat of decomposition was found to be near zero. The heat capacities of condensed-phase species and heats of combustion of evolved gases were also determined. The heats of combustion were found to vary over the course of decomposition—the trend captured by the model. Development of a complete pyrolysis model for this material will be a subject of Part II of this work.