The Effects of Oxygen Contents and Heating Rates on Characteristics of Pyrolysis Prior to Smoldering of Flexible Polyurethane Foam

The Simultaneous Differential Scanning Calorimeter-thermogravimetric analyses (DSC-TGA) apparatus was used to investigate the influences of different oxygen contents and heating rates on properties of pyrolysis phase (from room temperature to 800) prior to smoldering establishment of polyurethane foam. Results show that reduction of both oxygen content and heating rate show inhibition effects on the pyrolysis of polyurethane foam, i.e., both cases can reduce the propagation rate of smoldering and the possibilities of its transition to flaming. The reduction of the heating rates mainly prolongs pyrolysis cycle, and thus the concentrations of produced volatiles and heat release rates are both descended. However, the influence of oxygen contents on polyurethane pyrolysis is relatively complicated. When oxygen content is less than 10% (volume ratio in mixed nitrogen-oxygen atmosphere), it is the decomposition temperature of polyurethane foam that is enhanced; when the oxygen content is between 10% and 50%, it is the pyrolysis rates, heat release rates and the amount of heat release that are reduced. In addition, the reductions of oxygen contents and heating rates inhibit the decomposition process of polyol that are the main material and energy source to maintain the smoldering propagation or its transition to flaming of polyurethane foam.