A new model to predict pyrolysis, ignition and burning of flammable materials in fire tests A.Yu. Snegirev a,n , V.A. Talalov a , V.V. Stepanov a , J.N. Harris b a Saint-Petersburg State Polytechnic University, Department of Fluid Dynamics (Thermal Physics), Polytechnicheskaya, 29, Saint-Petersburg 195251, Russia b Boeing Research and Technology, MP&ST, Elastomers Group, PO Box 3707, MS 19-LF, Seattle, WA 98124-2207, USA article info Article history: Received 5 February 2013 Received in revised form 21 March 2013 Accepted 24 March 2013 Keywords: Pyrolysis Gasification Flammability Polymer composite Ignition Burning abstract 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. & 2013 Elsevier Ltd. All rights reserved. 1. Introduction Quantitative prediction thermal decomposition, ignition and burning of solid combustibles is a challenging task which has not yet been resolved despite long history of research. In its turn, a versatile and well validated modeling methodology would offer an opportunity of predicting flame spread over solid combustibles and closing the feedback between combustion in the gas phase and solid fuel gasification—driving force of the fire growth in a realistic fire scenario. It has been recognized that further progress in CFD fire modeling cannot advance without capability to predict flammability of real materials with the same level of fidelity as that in description of the gas phase [1]. Another important application is the prediction of an expected outcome of large scale fire tests, which could reduce the number of tests required for the material certification. This is particularly important in the aircraft industry, which strengthens regulations limiting the heat release rate of the cabin interior components and, at the same time, increasingly applies new lightweight, combustible polymers and composites for aircraft interiors and structures [2]. Reduced flammability materials would eliminate catastrophic inflight fuselage fires and provide more escape time for a passenger in a postcrash fire. Standard methodologies, such as that implemented in OSU apparatus [3] are time-consuming, they produce the sample size- dependent outcome and may exhibit lack of repeatability. This inspired development of the novel testing methodology, microscale combustion calorimetry, MCC (ASTM D7309-07a) [4], which inherits the accuracy of classical thermal analysis techniques (TGA and DSC) and has the advantage of predicting heat release rate in volatile combustion. The MCC measurements provide information of two types. First, material properties, such as the heat release capacity and characteristic temperatures, can be evaluated for further use as flammability indicators. Second, a kinetic model and associated kinetic parameters can be derived and then used as the input data of the pyrolysis model. It has been reported in the literature that for some polymeric materials the heat release capacity measured in MCC experiments correlates with the parameters measured in conven- tional fire tests such as cone calorimeter peak heat release rates (ISO Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/firesaf Fire Safety Journal 0379-7112/$ - see front matter & 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.firesaf.2013.03.012 n Corresponding author. Tel.: +7 812 2944276, mobile: +7 9216494754. E-mail addresses: a.snegirev@phmf.spbstu.ru, a.snegirev@mail.ru (A.Yu. Snegirev). Fire Safety Journal 59 (2013) 132–150