Study On Melting And Flowing Combustion Behavior Of Typical Thermoplastics In Compartment

Polymer materials, due to its easy manufacturing, light weight, low cost, waterproof and corrosion resisting, are widely used in many fields of social development, which is the fourth building materials after cement, steel and wood now. Polymer materials contain two different kinds:thermoset and thermoplastic. When subject to fire, thermoplastics would release lots of heat and toxic smoke. At the same time, pool fire will also be generated on the floor for the melting, dripping and flowing behavior of thermoplastics. It will extend fire area and accelerate room fire development with much more serious fire losing.Previous studies on combustion behavior of thermoplastics were mainly in the open space, and most of which were focused on the pyrogenation and combustion process of bench-scale samples. Big differences are existed between those bench-scale works and real room fire scenario. The object of this dissertation is to select one typical thermoplastics (Polypropylene sheet), and study the melting and flowing combustion behavior of thermoplastics in compartment using both theory and experiment methods.Through thermal analysis experiment tests, the affects of temperature increase velocity and ambience condition to pyrogenation process were studied. Pyrogenation temperature and melting temperature of sample were also obtained. The three factors of pyrogenation kinetic process were calculated by isothermal analysis and non-isothermal analysis.The affects of sample thickness and exterior radiation condition to ignition time, heat release and mass loss rate were studied through fire experiments on cone calorimeter. According to the characteristic of melting ignition process, a prediction model of ignition time for thermoplastics was set up. Comparing with the fire experiment results, it showed that this model could well calculate the ignition time of thermoplastics.An experiment test instrument, which was used to investigate the complex combustion behavior of large-scale thermoplastics in compartment fire, was designed on the basis of ISO9705. Lots of large-scale fire tests experiments of thermoplastics were completed, in which several affect factors, such as sample thickness, distance between sample and floor level and ventilation condition, were considered. Some fire dynamics parameters, such as heat release rate, temperature field of sample surface, hot smoke temperature in room and toxic gas concentration, were obtained. The experiment results showed that the peak heat release rate increased as the sample thickness increasing, but the time to peak status decreased as the sample thickness increasing; the interaction intensity between wall fire and pool fire was determined by distance between sample and floor level; two-dimention fire spread velocity of sample surface increased with time as exponential form; the peak heat release rate was affected by both ventilation factor and intake height, the relation of which was linear.On the basis of free fire plume theory, peak heat release rate prediction model for thermoplastics was put forward. Comparing with the experiment results based on ISO9705, it showed that this model could well calculate peak heat release rate for thermoplastics in compartment fire.