Impact of Pyrolysis Behavior and Residue Formation on Fire Growth Predictions in Polymer Fires

In this study, representative polymer fuels, namely acrylonitrile-butadiene-styrene (ABS) and polyvinyl chloride (PVC), were examined by conducting cone calorimeter experiments based on ISO 5660-1 and numerical analysis using the fire dynamics simulator (FDS) to quantify the effects of pyrolysis characteristics and residue formation mechanism on combustion predictions. The results revealed that ABS, a non-charring fuel, exhibited simple pyrolysis reactions and single-peak characteristics of the heat release rate (HRR) and showed good agreement with the numerical model. By contrast, PVC exhibited complex combustion suppression behaviors, releasing non-flammable HCl gas upon thermal decomposition and forming a thick residual layer that inhibited heat transfer and oxygen diffusion. The FDS overestimated the HRR and total heat release (THR) by approximately 2.6 and 2.1 times, respectively. However, the predicted mass loss rate (MLR) was similar to the experimental results for both ABS and PVC, indicating that the FDS reflected the mass-loss-centric pyrolysis behavior relatively well. For PVC, the numerical model did not adequately implement the heat-shielding and flame-suppression effects observed in the experiment, resulting in significant errors in the HRR and THR. However, the predicted MLR was similar to real-world values. These results suggest that although the prediction reliability of FDS is high for fuels with simple pyrolysis characteristics, it is limited for fuels with a complex suppression mechanism. Therefore, metrics based on physical values such as the MLR, HRR, and THR must be utilized when predicting combustion.