Study On The Scale Law Of Release Of Smoke Gas Of Thermoplastic Polymer

Thermoplastic polymer material is widely used in the various fields because of its excellent properties.Most polymer materials are flammable,and its combustion will release a lot of heat,CO,HCN and other toxic and harmful gases.About 80 percent of deaths in building fires are caused by the smoke and toxic gases.In this paper,the factors affecting the release of smoke gas during the combustion of thermoplastic polymer materials and its release laws were studied.Cone calorimeter and smoke density box were used to study the combustion performance of material and the law of emission of smoke.Finally,based on previous steady-state tube furnace experiments,fire dynamics simulator was used to establish multi-scale fire models,and numerical simulation was carried out to explore the scale law of toxic gas release of thermoplastic polymer materials.Firstly,in the small scale fire test study of thermoplastic polyurethane materials,the cone calorimeter experiment of different sizes of samples was carried out,and the combustion performance parameters were analyzed.The ignition time increased with the increase of thickness.The increase of thickness made the internal thermal conduction process longer,so that the peak of heat release rate,smoke release rate and the time to reach them also increased.The values of fire growth index and fire growth rate index basically increased with the decrease of the width.The total heat release index,smoke factor and ignition index were greatly affected by the thickness.The values of THRI and SF increased with the increase of the thickness,while the latter decreased.Secondly,three kinds of thicknesses of TPU were selected,and smoke density box method was adopted to analyze the smoke emitted by the materials in the combustion process.The smoke toxicity index was further calculated.The release of toxic gases(CO?HCN)increased with the increase of thickness.The values of CITG and FED both increased with the increase of the thickness,and the relationship between them was approximately linear.Thickness had an important effect on the smoke density parameters,which affected the test results of the smoke density.Finally,based on previous steady-state tube furnace experiments of toxic gas release of thermoplastic polymer materials,numerical simulation was carried out to explore the scale law of toxic gas release of thermoplastic polymer materials.FDS was used to establish multi-scale fire models.The Froude number was guaranteed to be constant.The results showed that as the experimental scale increased,the CO concentration around the fuel and the FED value also increased.When the ventilation condition changed from good to poor,the growth rate of CO concentration and the FED value increased with the increase of the experimental scale,and the two parameters basically satisfied a linear function relationship.When the ratio of experimental scale was small,the CO concentration and the FED value both increased with the increase of the dimensionless vent area.When the ventilation condition changed from good to poor,the growth rate of CO concentration and the FED value increased with the increase of the dimensionless vent area.