Fire behaviors of vertical and horizontal polymethyl methacrylate slabs under autoignition conditions

Abstract

In this study, horizontal and vertical black polymethyl methacrylate (PMMA) samples were investigated experimentally and theoretically under 25‐70 kW/m2 heat flux with autoignition conditions. An empirical model was developed to predict the autoignition time, where the significance of this model is to unify the prediction for both horizontal and vertical samples. Both horizontal and vertical samples show similar phenomena, such as burning stages and no higher than 2 cm sample expansion. It is obtained that the vertical samples show averagely 21% lower CO yield and also longer ignition time than those of the horizontal samples, while the CO2 yield increases about 24%. However, the vertical samples show a relatively high fire risk. This can be reflected by higher surface temperature, bigger average heat release rate (HRR) and mass loss rate (MLR), higher peak MLR, longer bubbling stage, higher CO2 yield, where the differences become even bigger under a higher external heat flux. A linear relationship was found between the average HRR of vertical and horizontal samples, and also between the ignition temperature and external heat flux for both orientated samples. The research outcomes provide a practical basis and guide for the risk assessment of combustible materials under both vertical and horizontal orientation.

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

“…A comparison between measured and predicted t ig , T sig, and m sig in the range of heat fluxes 25-150 kW/m 2 is also carried out for the spontaneous ignition in Figures 10-12, respectively. As most of the measurements [23,25,28,52,[55][56][57][58] refer to clear PMMA, simulations have been carried out for clear LMW and HMW PMMA with thermal and thermo-oxidative kinetics, but results for black LMW and HMW PMMA with thermo-oxidative kinetics are also included for comparison. As expected, it can be observed that the best agreement between predicted and measured t ig is obtained with the data of clear LMW PMMA with thermo-oxidative kinetics.…”

“…The inverse of the square root of the spontaneous ignition delay time as a function of the heat flux, Q, as predicted for clear and black LMW (solid and dotted blue lines) and HMW (solid and dotted brown lines) PMMA with thermo-oxidative decomposition kinetics and for clear LMW (dashed blue line) and HMW (dashed brown line) PMMA with purely thermal decomposition kinetics.Experimental data (symbols) derived from the literature are also reported. (See Refs [25,28,[55][56][57][58]…”

“…Several experimental data (symbols) derived from the literature are also reported. (See Refs [57,58]…”

A review of thermal properties of timber and char at elevated temperatures

“…cross-laminated timber 10 ) The determination of the thermal properties for timber is much more challenging than those isotropic construction materials, such as steel, 11 concrete 12 and polymers. 13 For example, as an anisotropic material, timber’s thermal conductivity to the fibre orientation is generally twice of that perpendicular to fibre. 14 Some of its characteristics even complicate the situation, such as internal moisture 15 and pyrolysis behaviours under a high-temperature environment.…”