Study On Downward Flame Spread Characteristics Of Typical Thermosetting And Thermoplastic Insulation Material

With the rapid development of economy,the construction field is facing a comprehensive transformation oriented by energy conservation and environmental protection.Rigid polyurethane foam(PUR)and Extruded polystyrene foam(XPS)are widely used in construction industry because of their superior thermal insulation performance.Rigid polyurethane foam belongs to thermosetting material and extruded polystyrene belongs to thermoplastic material,the combustion of the two materials is also different because of their different material properties and structural characteristics.However,these polymer thermal insulation materials usually have certain flammability.Once the protective layer of the building wall falls off or breaks down,the thermal insulation materials in the sandwich will be ignited quickly after an unexpected open fire,and these two materials will burn to produce toxic gases,and the fire spreads very fast,resulting in huge potential safety hazards.The research on the fire spread behavior of building exterior wall insulation materials has become a key problem in the field of building safety.In this paper,the downward flame spread device is used to conduct downward flame spread behavior of Rigid polyurethane foam(PUR)and Extruded polystyrene foam(XPS)with different widths.The downward flame spreading characteristics of PUR and XPS with widths of 5cm,10 cm,15cm and 20 cm were studied in this research.A series of important parameters,such as flame height,flame spread rate,mass loss rate and flame pulsation frequency were investigated in the experiment.Combining with theoretical knowledge,the effects of the above parameters on the fire spread of PUR and XPS materials are analyzed and revealed.The experimental and theoretical analysis show that downward flame spread of PUR and XPS have a positive correlation with the flame spread rate,the flame height and the mass loss rate.In the same environment,the wider the width of the foam and the faster the flame spread rate,and the smaller the flame pulsation frequency is with the increase of the width of the foam.Through the analysis of the surface temperature field of PUR and XPS,it is found that the downward flame spread of PUR materials is relatively stable.The maximum surface temperature of PUR materials is about 700?,and that of XPS materials is about 600?.The main reason is that when XPS material spreads,melting droplets will take away part of the heat energy and reduce the flame temperature.