A new model to predict pyrolysis, ignition and burning of flammable materials in fire tests

• New comprehensive model to predict thermal performance of polymer composite materials is presented.
• Formal kinetics of material thermal decomposition uses measurement-based kinetic function.
• Calibrated and validated for non-charring, charring intumescent polymer, and the fiber-reinforced composite.
• Key model parameters affecting model predictions are identified.

New comprehensive model, Pyropolis, aimed to predict performance of polymer composite materials exposed to radiative heating is presented, and a procedure to derive kinetic model of material thermal decomposition from either TGA or MCC measurements is introduced. In this procedure we do not pre-assume a kinetic function, but derive it from the measurements thereby achieving model validity in a wide range of heating rates. The Pyropolis model is capable of predicting thermal decomposition of both charring and non-charring polymers; in case of charring polymers, material intumescence is assumed to be controlled by the amount of char produced in decomposition reactions, given the intrinsic char porosity. Current version of the Pyropolis model has been calibrated and favorably validated for three types of flammable materials: non-charring polymer (high impact polystyrene), charring intumescent polymer (BPA polycarbonate), and the fiber-reinforced resin composite, all exposed to external heat flux. The model is demonstrated to be able of predicting test outcome (time to ignition, peak and average heat release rate) with a reasonable accuracy, provided material properties and test conditions are adequately identified. Sensitivity studies revealed the model components which have the most pronounced effect on the predictions. Sample surface emissivity, expansion propensity, and char layer conductivity are the key parameters controlling simulation results for charring polymers. For non-charring polymers, volumetric radiation absorption and availability of black coating film are important factors affecting the rate of virgin material gasification.