Expanded Polystyrene is derived mainly from styrene monomer and is expanded to form an essentially closed cell structure. When considering the fire behavior of any construction material, it is important to realize that the evaluation must be based on its behavior under final conditions of use. This behavior will depend not only on the chemical nature of the material but largely on its physical state.
EPS is flammable, as is the case with many other building materials. However, this is only relevant if EPS is evaluated as an exposed insulation material.
How the fire develops in a building
When a building has normal temperature conditions in its daily use, there is a natural balance between flammable materials and ambient oxygen. However, in the first stage of a fire, the ignition energy comes into contact with the flammable material. Above a temperature of approximately 200 ºC, the material will release flammable gases, which will burn due to both the original ignition and spontaneously. In the case of gases, combustion can directly lead to the generation of flames, while solid materials, such as furniture, must first become incandescent sources of ignition.
In the first stage of a fire, there is a gradual accumulation of heat energy in the form of combustible gases. At this point the temperature is still relatively low and the fire is still located inside the building. Later, a sudden development occurs, called a "flash-over," in which the temperature rises significantly and the fire suddenly spreads throughout the compartment. After this sudden development or "flash-over" the chances of rescuing people and equipment are greatly reduced
EPS behavior in a fire
In order to calibrate the different risk situations that the use of EPS makes up, factors derived from its content, its form and its environment must be taken into account. The fire behavior of EPS materials can be modified by applying coatings and coatings.
The development and extent of the fire depends, in addition to the intensity and duration of the fire, on the specific properties of the raw materials used in the manufacture of the expanded polystyrene.
The raw materials of the expanded polystyrene are styrene polymers that contain a mixture of low-boiling hydrocarbons as a blowing agent. They are all combustible materials. The blowing agent (pentane) progressively volatilizes in the transformation process. The residual 10% requires a storage phase for a time depending on the product specifications: dimensions, density, etc.
The calorific value of Expanded Polystyrene materials (40 MJ / kg) is approximately twice that of wood (18.6 MJ / kg), but taking into account the densities of both products, the calorific volume for Expanded Polystyrene is between 540 y1250 MJ / m3 and in the case of products from cellulose, wood fiber or wood is between 7150 and 10400 MJ / m3.
EPS contains a small amount of fire retardant agent (maximum 0.5%). It is the fire retardant EMERALD 3000, polymeric brominated designed to be friendly to the environment. This has a beneficial effect when EPS is exposed to a fire source. The foam shrinks quickly by withdrawing from the heat source, thereby reducing the likelihood of ignition. The decomposition products of the additive cause the flame to extinguish, so when the ignition source is removed, the EPS does not continue to burn.
A material treated with self-extinguishing agents contracts if exposed to a flame. It will only start to burn if the exposure is prolonged, at a very low speed of spread, the flames spread only on the surface of the material.
In the absence of an ignition focus, the thermal decomposition products do not ignite until temperatures of the order of 400 - 500 ºC are reached. When exposed to temperatures above 100ºC, the EPS products begin to soften slowly and contract, if they increase in temperature they melt. If it continues to be exposed to heat for a certain time, the molten material emits flammable gaseous decomposition products. In this regard, a table is attached with the composition of these gases, comparatively with those emitted by other common products in buildings.
Carbon monoxide can be fatal if inhaled for 1 to 3 minutes at concentrations of 10,000 ppm (parts per million) to 15,000 ppm. Styrene has a characteristic odor that can be detected in concentrations between 25 ppm and 50 ppm and that becomes unbearable between 200 ppm and 400 p
