E-cars are on the rise and pose an ever greater challenge – for fire departments and towing services, garages and parking garage operators, even ferry companies. In the event of a fire, emergency personnel must be able to act quickly and effectively to protect the surrounding area and prevent major damage. An important role in this context is played by the
large-format extinguishing blankets specially developed for fighting fires in e-cars. Because battery fires are difficult or impossible to extinguish, the term fire limitation blanket has become popular. This article discusses the advantages and disadvantages of the different types of these fire-rated blankets.
Mode of operation of large-format fire barrier blankets
Large-sized fire blankets are usually made of fire-resistant materials. They can be placed on the burning car to prevent the fire from spreading to other objects, i.e. surrounding vehicles.
or even the building fabric, to prevent. The blankets reduce the spread of smoke and heat and give responders more time to fight the fire.
What criteria play a role in the evaluation of fire blankets?
They should be easy to handle and, if possible, reusable. At the same time, they should be optimally designed for the special aspects of e-fires.
Let’s look at the meaning of the different properties in detail.
Conductivity
Conductivity is an important factor in choosing the right material. For example, modern e-cars do have cut-off systems designed to ensure that no electricity flows in the event of an accident or fire. But does it always work?
If a fire blanket is conductive, then it can quickly dissipate electrical current and prevent the fire from spreading. However, if a blanket material is used that is a good electrical conductor, the risk of personal injury is increased. Electric shocks may occur if bodies come into contact with the current flow.
So most manufacturers forgo the current dissipation aspect and use material that is non-conductive.
Health concerns
The main concern here is whether fibers or particles can be emitted and possibly inhaled. Among other things, this can lead to long-term damage to the lungs.
Multiple usability
When considering whether a fire blanket can be used multiple times, strength is considered, but flexibility is also considered. If a material becomes stiff and brittle after exposure to heat, it is not suitable for multiple uses. If, on the other hand, it remains flexible and retains its effectiveness against fires, it can be used several times.
Tear and cut resistance
A fire blanket is subjected to high loads. The material must withstand a high tensile force when the blanket is placed over a vehicle. Crashed vehicles often have dangerous, sharp edges. Most often, the entire weight of the blanket is moved by two handles. If the blanket tears, it can not be reasonably put on.
The same applies to the removal of the blanket. Protruding tips or edges can damage the blanket.
Temperature resistance
Heat resistance is a decisive factor. It depends on the material composition. In addition to the choice of material, the grammage and the thickness of the coating also play a role. A thicker or coated blanket may have higher heat resistance than a thinner or uncoated blanket of the same material. The temperature load capacity can only be considered in combination.
Weather resistance
Here we are talking about the effects of UV light, temperature fluctuations and moisture on the material or combination of materials, because most blankets consist of a base fabric with a coating.
What materials are used for large-format fire containment blankets for e-car fires?
The properties of the material used are reflected in the properties of the final product. Modern fire blankets often consist of
combinations, are specially treated or coated. It is important to match the strengths and weaknesses of a material to the specific application.
Base material silica
Base Material E-Glass
Silica
Silica materials consist almost exclusively of silicon dioxide SiO₂. This is one of the most abundant minerals on earth and exists in many different crystal forms: as quartz, silica anhydrite or sand. In the construction industry, it is indispensable in the production of cement and concrete. Due to the enormous fire and temperature resistance, chemical as well as UV radiation resistance, materials made of silica are preferred where fire resistance is essential as a barrier against the spread of flames, but also resistance to aggressive chemical media or radiation energy plays a supporting role.
E-glass
Due to its special inorganic composition, E-glass has excellent electrical insulation properties, very good mechanical strength and continuous temperature resistance up to 550 °C. The glass fibers spun from E-glass are widely used mainly as reinforcing fibers in plastic processing industries, for thermal and electrical insulation purposes and fireproof textiles. This is where the incombustibility pays off.
However, E-glass is not suitable for permanent temperatures above 650 °C. The glass fibers change their structure in these areas and massively lose mechanical stability.
Base material special glass
Base material carbon
Special glass fiber fabric
Special glass fiber mesh is a material made of glass fiber reinforced plastic. It is lightweight and provides good electrical insulation. The low thickness of the fabric allows to create compactly packaged fire barrier blankets. Its temperature resistance of 1,000 °C over a longer period of time withstands a battery fire just fine.
Carbon
Carbon is a colloquial term for the chemical element carbon and its derived products. Materials made of carbon fibers are characterized – despite their low weight – by enormous mechanical and thermal load-bearing capacity. There is also good resistance to chemicals (e.g. most acids and alkalis).
Its good electrical conductivity is useful for many applications – but rather a cause for concern in fire blankets.
Coating with vermiculite
Coating with silicone
Vermiculite
This rather rare layered silicate is considered incombustible. It has a high melting point (approx. 1,315 °C) and is electrically non-conductive. However, it is porous, absorbs leaking chemicals, for example, and for this reason is used as a filler by waste collectors when storing lithium-ion batteries.
Silicone
Special silicone is used as a coating. It usually protects the blanket fabric from both sides. Because UV light, moisture or temperature fluctuations cannot harm it, but despite its impermeability it has a high flexibility, it is ideally suited.
So how do the different fire blankets perform in the evaluation?
Silica blanket – e.g. VLITEX Silica
This fire blanket is often used when it is not allowed to use silicone. In some highly technical areas, this is the case. Indeed, vermiculite is the substance used for coating silica blankets.
One then accepts the disadvantages of the material, stores it as far as possible without the influence of UV light or temperatures and disposes of the blanket after one use. This is especially necessary because the vermiculite coating soaks up liquids (usually chemicals, but at least contaminated water) that can no longer be removed.
Vermiculite is much worse protects the fibers of the blanket from sharp edges. The blanket is more prone to cracking. In addition, the smoke and gas retention effect is much lower. The coating simply does not seal as strongly as the silicone coating.
One argument in favor of the silica blanket is its higher temperature resistance. Only – this is a weak argument, because even battery fires don’t get that hot. Our measurements during trials recorded peaks of just 1,300 °C. For this, the silica blanket is basically disproportionate.
Limited recommendation from us – just for the cases mentioned above.
E-glass blanket – e.g. VLITEX Fire blanket Premium S
Usually “only” 600 – 800 °C are measured for Li-ion fires – the E-glass blanket can cope with these. However, short outliers upwards are always to be expected, and that’s where the material shows weaknesses. An e-glass blanket is also – despite silicone coating – not suitable for multiple use. It is usually subjected to too much stress during use.
Recommendation therefore for areas with a high fire risk, in order to be able to react quickly and carry out safety measures until the arrival of the fire department.
Special glass blanket – e.g. VLITEX Fire blanket Premium M
The fire protection blanket made of special fiberglass fabric with silicone coating on both sides is convincing. It is tear-resistant, harmless to health and does not conduct. Because it remains flexible yet firm when exposed to prolonged heat, it is quite suitable for multiple uses.
It is the only blanket certified for use on Li-ion fires.
Carbon blanket
A carbon fire blanket with silicone coating is conditionally suitable for use with lithium-ion fires. On the one hand, it scores with weather resistance and high tear strength. On the other hand, the electrical conductivity and the risk of lung damage from fibers are serious disadvantages.
We are not convinced.
Summary
In this blog, we have considered the four main materials for fire-rated blankets: Silica, E-glass, Special glass and Carbon. To do this, we looked at the different coatings, vermiculite and silicone. Each material has its strengths and weaknesses, usually the full impression is only revealed in the evaluation of the overall composition.
Combating battery fires, especially in e-cars, is an important safety issue. Careful consideration of the various materials used in fire containment blankets can help provide an effective solution for containing and suppressing such fires.
VLITEX
