Beijing CCTV building fire, Shanghai Jiaozhou Road classroom apartment fire, "6·14" London high-rise apartment fire... In recent years, high-rise building fires have attracted more and more attention. In these fires, three-dimensional combustion of the façade insulation layer occurred, which accelerated the spread of fire and caused heavy casualties and economic losses.
As a green energy-saving measure, many high-rise buildings now have an insulation layer on the façade and a protective layer on the outside of the insulation layer. However, in fact, the choice of insulation material is very mysterious, and different materials will produce different results after the fire. On the afternoon of September 29, the provincial fire brigade teamed up with the Hangzhou Fire Brigade to conduct combustion experiments on different insulation materials in the Qibao Community of Pengyu Street, Jianggan District, Hangzhou to test the combustion performance of different materials.
Three common insulation materials were selected for the experiment: flame retardant extruded polystyrene board, flammable rigid foam polyurethane and flammable polyethylene foam board. Before the experiment, the firefighters selected two independent brick-concrete structures in the Qibao community to be demolished. Three kinds of insulation materials were used to make the outer facade of the insulation layer by different techniques, and then covered with damaged protective layer and covered. Experiment with both cases of intact protective layers.
Experiment 1: Flame retardant insulation material VS flammable insulation material
Before the experiment, the firefighters first compared the combustion performance of the two insulation materials. They each found a flame-retardant extruded polystyrene board and a flammable polyethylene foam board, and then ignited two insulation materials with a lighter. After the extruded polystyrene board encounters an open flame, the edge portion begins to slowly zoom black with a small amount of black smoke, but after the lighter flame is extinguished, the extruded polystyrene board does not continue to burn; and after the polyethylene foam board is ignited, The flame spreads rapidly and there is a constant flow of foam melt with an open flame.
Then the experiment begins. According to the common fire situation, a firefighter ignites the burning material in the room, and the outside of the room is an extruded polystyrene board insulation layer covered with a broken protective layer. At the same time, another firefighter ignites combustibles directly at the bottom of the layer of polyethylene foam board insulation covering the damaged protective layer.
Extruded polystyrene board is not ignited
After 1 minute, the inner room of the outer facade of the flame-retardant extruded polystyrene board insulation layer began to burn fiercely, and the window position continued to have a flame to the outer wall, but the outer layer of the insulation layer was not baked more black. No other changes occurred; the flame at the bottom of the flammable polyethylene foam board insulation layer did not have a large fire in the room, but the insulation material was quickly melted to expose a large area of cement wall.
Polyethylene foam board burns quickly after ignition
Polyethylene foam board begins to burn
The open fire in the room began to burn fiercely
After 10 minutes, the combustibles in the room inside the layer of flame retardant insulation material are slowly burned out, the flame begins to become smaller, and the facade is not irritated except for part of the protective layer falling off and the insulation material is blackened, and there is no other abnormality; The layer of insulation material has burned and the melt with open flame is continuously dripping, resulting in a significant increase in the fire at the bottom, and the exposed area of the cement wall is also expanding.
Extrusion polystyrene board still does not burn after the protective layer falls off
"The comparative experiment effect of the two insulation materials is obvious. As a thermal insulation material, the polyethylene foam board is very dangerous, not only will it burn itself, but the melt is likely to drip with the wind, causing the fire to spread." Xu Wei, senior engineer of the provincial fire brigade told Reporters, fire fighting and rescue of high-rise building fires is difficult, and it is generally carried out by taking the tactics of controlling and then extinguishing fires. However, the melting of flammable insulation materials will make the spread of fire uncontrollable, and will greatly increase the difficulty of rescue on site.
Experiment 2: Inflammable material covering the intact protective layer vs. combustible material covering the intact protective layer
In the second experiment, the firefighters installed a flame-retardant extruded polystyrene board covered with a good protective layer and a flammable rigid foam polyurethane covering the intact protective layer on the facades of the two rooms. Subsequently, two firefighters ignited combustibles in the room.
Residential houses covered with two different protective layers
After 1 minute, the open flames in the two rooms began to burn fiercely, and the flames were rolled around the window with the black smoke. The surface of the window of the façade of the combustible insulation material had a short-term combustion at the initial stage, and the surface of the protective layer of the two insulation materials. There are almost no abnormalities.
After the experiment started, the firefighters started to ignite.
After 5 minutes, the fire in the two rooms was still burning, and the edge of the window of the refractory insulation material began to be blackened, but in addition, the surface of the protective layer of the two kinds of insulation materials did not appear to be damaged. Nothing burns.
After 10 minutes, the fire in the two rooms gradually became smaller, and the surface of the protective layers of the two insulating materials remained unchanged.
Insulation material covering the intact protective layer does not burn under flame baking
“There is no obvious change, and it has a great relationship with the integrity of the protective layer.” Xu Wei explained that the insulation of the façade of the high-rise building is not only important, but the construction process of the protective layer is also not to be underestimated. After the wall is subjected to high temperature baking, the protective layer on the surface of the thermal insulation layer will expand and contract, and the hollowing phenomenon will be easily formed between the wall and the wall, which will lead to sufficient oxygen to enter the thermal insulation layer, thereby causing the three-dimensional combustion of the thermal insulation layer. To accelerate the spread of fire."
Xu Wei said that the current common insulation materials on the market mainly include extruded polystyrene board, rubber powder polystyrene granule insulation rubber, hard foam polyurethane, polyethylene foam board, etc., but it should be noted that, in addition to extrusion polystyrene board And the rubber powder polystyrene granule insulation compound belongs to the B1 grade flame retardant material that meets the requirements. The B2 flammable rigid blister polyurethane and the B3 flammable polyethylene foam board are all not in compliance with the requirements. In the Code, the relevant regulations for the façade insulation layer, the use of qualified materials, the use of correct construction measures to ensure good construction process and quality, in order to ensure the fire safety performance of the building.