Assessment of the predictive capabilities of a solid-gas model for poly (methyl methacrylate) ignition

Effects of the PMMA Molecular Weight on the Thermal and Thermo-Oxidative Decomposition as the First Chemical Stage of Flaming Ignition

“…For the development of predictive models, chemical and physical processes should be described with accuracy levels depending on specific requirements for the predictions. In accordance with the literature review reported in [7,8], the first class of PMMA ignition models consists of condensed-phase descriptions coupled with empirical ignition criteria [9][10][11][12][13][14][15][16][17][18][19]. Another model class is based on descriptions of both the condensed and gas phases [7,8,[20][21][22][23][24][25][26][27][28][29], which do not require the use of empirical criteria.…”

“…In accordance with the literature review reported in [7,8], the first class of PMMA ignition models consists of condensed-phase descriptions coupled with empirical ignition criteria [9][10][11][12][13][14][15][16][17][18][19]. Another model class is based on descriptions of both the condensed and gas phases [7,8,[20][21][22][23][24][25][26][27][28][29], which do not require the use of empirical criteria. These include both simple unsteady onedimensional models, which give quantitative information on the main global parameters (e.g., ignition delay time, surface temperature, and volatile mass flux at ignition), and more advanced CFD formulations.…”

“…To quantify the influences of such variability on ignition predictions, an extensive sensitivity analysis has been recently carried out for a one-dimensional solid-gas phase model [7]. For both the spontaneous and the piloted cases, the highest sensitivity concerns the kinetics of polymer decomposition [8]. It is interesting to observe that despite the improvements in the mathematical description of the flaming ignition of PMMA when the empirical criteria of the models [9][10][11][12][13][14][15][16][17][18][19] are substituted by rigorous formulations of conservation equations for mass and energy coupled with combustion kinetics by models [7,8,[20][21][22][23][24][25][26][27][28][29], a global single-step mechanism is always used for the polymer decomposition into monomers.…”

“…In particular, the PMMA molecular weight determines important features of the decomposition mechanism that turns from a one-stage global reaction (low molecular weight) [7,[31][32][33] into a multistep process (high molecular weight) [17,34]. However, none of the literature models combine multistep decomposition kinetics with the description of either solid phase physical processes only [9][10][11][12][13][14][15][16][17][18][19] or both solid and gas processes [7,8,[20][21][22][23][24][25][26][27][28][29]. Hence, the subsequent impact of the polymer molecular weight on the ignition behavior has never been investigated.…”

“…These are the central topics of this study. In fact, a comprehensive condensed-gas phase model, previously developed by [7,8], is used to investigate the effects of the PMMA molecular weight and thermal or thermo-oxidative decomposition on spontaneous and piloted ignition. More precisely, a single-step or a multistep decomposition mechanism for low and high molecular weight PMMA, respectively, is combined with the description of the main physical processes and the gas-phase combustion of methyl methacrylate (MMA) for conditions that reproduce those of the cone calorimeter and heat fluxes intensities in the range of 25-150 kW/m 2 .…”