Mass loss and flammability of insulation materials used in sandwich panels during the pre-flashover phase of fire

In this study, the mass-loss and flammability limits of different sandwich panels and their cores (PUR, PIR, stone wool, EPS and XPS) are studied separately using a special developed furnace. The focus is on the pre-flashover phase of fire (up to 400°C), because exceeding the lower flammability limit in this phase may lead to a smoke layer explosion, a hazardous situation for an offensive intervention by the fire brigade. The research has shown that the actual mass-loss of synthetic and stone wool based cores is comparable up to 300°C. From 300°C onwards, the mass-loss of PUR panels is significant. EPS and XPS cores become fluid before pyrolysis starts. Furthermore delamination of the panels can be observed at exposure to temperatures above 250°C for the synthetic and 350°C for the mineral wool panels. The lower flammability limits have been established experimentally at 39% m/m (PUR) and 36% m/m (PS) of the pyrolysis gasses on the air mass, respectively. For PIR and mineral wool no flammability limits could be established.