# Polyisocyanurate Foam Pyrolysis and Flame Spread Modeling
## 3 Results and Discussion  
### TGA and DSC Experimental Results and Modeling  
The mean TGA and DSC experimental data collected for the PIR foam samples at 10 K min\({}^{-1}\) in nitrogen are shown in Figure 3. The TGA data are plotted as sample mass, m, and MLR normalized by the initial sample mass, m\({}_{0}\), with respect to the sample temperature, \(T\). The DSC data are presented as heat flow and integral of heat flow, both normalized by m\({}_{0}\). The error bars were calculated from the scatter of the data as two standard deviations of the mean. According to the TGA data, the thermal decomposition of the foam begins at about 400 K and continues over a wide range of temperature. The MLR becomes insignificant around 900 K, at which point about 32 wt.% of material remains in the crucible. Figure 3: Mean experimental results and model predictions for the thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) tests performed on the PIR foam at 10 K min\({}^{-1}\) in nitrogen. During modeling of these data, the foam material was represented by a mixture 95.9 wt.% of reactive PIR component and 4.1 wt.% of inert glass fiber component. The amount of the glass fiber component was determined from the results of the TGA tests performed in air using open crucibles. The PIR component was assumed to decompose through seven consecutive first-order reactions with one condensed-phase, PIR_Int_#, and one gaseous, Gas_#, product to accurately capture the multipeak structure of the experimental MLR. The kinetic parameters of these reactions, including the pre-exponential factors, \(A_{r}\), activation energies, \(E_{r}\), and mass-based stoichiometric coefficients, were obtained through fitting of these experimental data. The results of this fitting exercise are shown in Figure 3; the optimized parameters are summarized in Table 1.  
The heat capacities, \(C_{p}\), of the condensed-phase components of Tuff-R foam core are summarized in Table 2. The heat capacity of the glass fiber component was obtained from the literature [41]. The PIR component heat capacity was determined by fitting the portion of the 10 K min\({}^{-1}\) DSC data preceding decomposition. The final residue (PIR_Int_7) heat capacity was obtained by fitting the results of separate DSC experiments performed on fully decomposed samples. The heat capacities of the intermediate condensed-phase products could not be determined directly and were assumed to be equal to the heat capacity of the PIR component taken at 420 K, which produced a reasonable sensible heat flow base-line shown in Figure 3. Finally, the heats of reactions, \(\Delta H_{r}\), were selected to fully reproduce the experimental heat flow and its integral. The values of the heats of reaction are summarized in Table 1. All reactions, with the exception of Reaction 4, were found to be endothermic or thermally neutral. The heat capacities of the gas-phase decomposition products could not be obtained from the current measurements and were assumed to be equal to 2100 J kg\({}^{-1}\) K\({}^{-1}\), which was the mean heat capacity of a collection of C1 to C8 hydrocarbons at a temperature of 600 K [20]. To ensure that the developed reaction model was capable of extrapolating to alternate heating rates, its predictions were compared with the experimental TGA and DSC data collected at nominal heating rates of 5 and 20 K min\({}^{-1}\). These comparisons are shown in