Pyrolysis characters and fire behavior of bus ceiling materials

The pyrolysis characters and fire behavior of ceiling materials have a great impact on the fire retardant of the whole bus because the fire might spread along the ceiling. This study investigated the pyrolysis characters of five plastic ceiling components with TG tests at four heating rates, and then, the kinetic parameters were calculated with Kissinger method, Friedman method and an advanced isoconversional Vyazovkin method. The obtained kinetic parameters were also validated by reconstruction of conversion curves. Finally, the flammability of each component from three ceiling materials was estimated using PCFC, and the fire behavior of three ceiling materials was investigated with cone calorimeter at different heat fluxes. Results show the pyrolysis characters of surface material could explain the early stage fire behavior of ceiling materials. The ignition and fire resistance were also highly dependent on the properties of surface materials. A transition between limited and more fierce combustion occurs at some heat flux for three ceiling materials. This property was related to the composition and structure of ceilings. Below this transition heat flux level, only the surface layer of ceiling was ignited and the fire load was limited. Above this level, the underlying layer was involved in combustion and leads to a sharply increased heat release. These results suggest that the flame retardant of surface material was important to promote fire retardant of the whole ceiling. Moreover, the obtained parameters can be used for predicting fire propagation in bus ceiling.