Fire protection research: materials that defy fire
Schwer entflammbare Materialien sind überall dort unabdingbar, wo sich grosse Menschenmengen aufhalten. Die Empa entwickelt solche Werkstoffe für ganz unterschiedliche Anwendungen. Welche Hürden es dabei zu überwinden gilt, erklärt Empa-Forscher und Materialexperte Sabyasachi Gaan.
Sabyasachi Gaan, when do we talk about flame-retardant and non-flammable materials?
The terms «flame-retardant» and «non-flammable» are often confused, but have very different meanings. Flame-retardant materials are generally flammable, but are difficult to ignite. This delays the spread of fires and allows more time for the evacuation of people and the arrival of the fire department. Flame-retardant materials are mostly organic materials. Some of them are inherently flammable, others are made flame-retardant, for example through additives, impregnations or coatings. Non-flammable materials, on the other hand, are usually inorganic, such as stones, cement, metals, ceramics and glass. They are considered fireproof and provide excellent protection against fires.
Where do you need flame-retardant materials?
Fire protection is needed wherever people move around in public and there is a risk of fire: in office buildings, theaters, stadiums, hospitals and so on. Not only should the building itself be flame-retardant, but also the furniture and interior fittings. Flame-retardant materials are also in demand in trains, airplanes and industry. In addition, protective clothing for the fire department, police, military and certain industrial sectors must of course also be flame-retardant.
What fire protection materials does Empa develop?
In my research group, we deal with organic materials. We have already developed coatings for wood and additives for wood-based materials. Another focus is on flame-retardant polymers, such as polyurethane foams, polyester fibers or epoxy resin. They are used in a wide variety of applications, for example in construction, transportation and interior design. Other research groups at Empa are working on further flame-retardant wood-based materials and non-flammable inorganic materials. And to support the emergency services in fighting fires, we at Empa are also developing efficient protective clothing and a heat-resistant «FireDrone».
What are the challenges in developing flame-retardant materials?
There are technical, economic and ecological challenges. Quite apart from fire protection, every new material must fulfill the purpose for which it is intended. If you make a material flame-retardant, you always change other properties as well. It can happen that you improve the fire behavior but worsen the weather resistance or stiffness - or make the material more demanding to process.
The new material should then be harmless to people and the environment. The manufacturing process should also have as little impact on the environment as possible, for example by avoiding the use of certain solvents. And finally, of course, the whole thing must be economical, i.e. it must not cost too much. When developing flame-retardant materials, we have to balance these three factors. In order to find the best solution, we have to understand and take into account the exact application of the material.
Strong projects
Empa researchers are developing protective clothing for firefighters (1), filigree and non-flammable sound absorbers (2), flame-retardant wood materials thanks to melon enzymes (3), recyclable composite materials for airplanes and trains (4) and the FireDrone (5), which can withstand extreme heat.
1. protective clothing
Firefighters must be able to perform in danger zones. Empa researchers are therefore working on reducing the stress caused by external heat radiation and steam development inside the protective clothing. Smart dummies and digital twins are important «research partners» here. In addition to insulating and thermo-reflective textiles, integrated early warning systems are being developed that provide real-time information on exposure and allow personalized predictions of how long rescue workers can stay in the danger zone.
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2. insulating materials
Thin, tailor-made and incombustible: Empa researchers have developed innovative sound absorbers made of mineral foams together with the company de Cavis. Not only are they significantly thinner than conventional materials, they can also be designed specifically for different frequency ranges. As they are made almost entirely from gypsum or cement, they are non-flammable and do not release any toxic gases or harmful particles.
3. wood material
What usually ends up in the oven today could protect houses tomorrow. Researchers at Empa and ETH Zurich have found a way to process sawdust into a hybrid material that is less flammable using a crystalline mineral binder. They used an enzyme from the seeds of watermelons to create a solid compound thanks to controlled crystallization. The new building material is therefore not only robust and flame-retardant, but also recyclable.
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4. composite materials
Aircraft and passenger trains are subject to strict fire protection requirements - and must also be mechanically robust and as light as possible. Glass and carbon fiber-reinforced composites meet these requirements - but have so far been almost impossible to recycle. Empa researchers have succeeded in producing a new type of epoxy resin that is both flame-retardant and recyclable. In an Innosuisse project with the Swiss company Elantas, they are now working on commercializing the material.
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5. FireDrone
Firefighters and industrial inspectors often have to work in extreme conditions - be it to assess hazards, locate victims or inspect infrastructure. The «FireDrone» will be the first drone to deliver real-time data from high-risk areas that are too dangerous for humans and conventional drones, even in extreme temperatures. Developed at Empa and continued by a spin-off, the new generation of drone combines heat-resistant polyimide aerogel insulation with practical robotics.
More information.
About the person: Sabyasachi Gaan
Empa scientist Sabyasachi Gaan is head of the „Additives and Chemistry“ team in the „Advanced Fibers“ laboratory in St. Gallen. Among other things, he specializes in research into flame-retardant materials.
