When a fire started coatings can play a major role in slowing it down. (Source: Анри Гор - stock.adobe.com)
17. Oct 2019 | Application Areas
Fire retardant coatings: “Many raw materials you traditionally add actually bring you in the wrong direction”
Coatings play a crucial role to protect us from the devastation that fires can bring. However, developing coatings that can prevent or slow down a spreading fire is very challenging. We spoke with Jens Ravnsbæk from Teknos, how to tackle those challenges and what trends he sees for fire retardant coatings.
Please explain how the European Construction Product Regulation (CPR) affects fire retardant coatings
Jens Ravnsbæk: This regulation aims to harmonise how we document and bring construction products on the European market. It sets out the guidance and rules for how we conduct technical performance testing and document the specifications of construction materials, to enable the same types of products, which are manufactured in different countries comparable. One of the things included within CPR is how you test, classify and document the performance of your products in relation to fire. This directly affects how we have to test and document a products performance, even though, it can be open for interpretation.
The fire performance in this regard is split into several types of testing. Here among others, we have fire resistance and the reaction to fire. Briefly explained, fire resistance is about how well a material survives in a fully developed fire. For this application I would like to call the coating products Fire resistance coatings. While reaction to fire is about how much a material will contribute to a developing fire. Here I would like to use the term for coating products Fire retardant coatings. Reaction to fire testing classifies materials in a Euroclass ranking from A to F. This has to do with how much a particular material will contribute to a spreading or developing fire.
I would imagine both types have their own types of tests?
Ravnsbæk: Fire resistant coatings, like the classic intumescent coatings, are tested according to the EN1363/64/65/66 etc. standards. Here, the construction material is typically subjected to a fully developed fire scenario and will give you information about how well your material will survive extreme temperatures and conditions. I am by no means an expert on fire resistance testing.
When you test fire retardant coatings towards reaction to fire performance, you measure how much energy this particular construction material contributes to a developing fire. The typical test for this is the single burning item (EN13823) test. Here you create a room corner and the test simulates a fire starting in a trash can and how the material at the room wall will either accelerate or decelerate the flame spreading and fire development.
So, you use a coated product for this test?
Ravnsbæk: Typically, you test a construction material that is as close to the final product as possible. Our fire-retardant coating is not classified as a construction material on its own, hence we are required to go to our customers product level. For example, you have a coating that is supposed to be used on spruce plywood with a density of 420 kg/m³, then you would test your coating to that kind of wood, in the desired dimensions your customers would use it. So, we need a certain insight into the markets we are targeting with our products.
Can you describe the process of developing fire-resistant coatings?
Ravnsbæk: It is not totally different than for other coatings, we are still looking at a lot of parameters that are important for other coatings too. But the primary function our fire-retardant coatings are required to give is improved reaction to fire performance. Meaning, when you evaluate new raw materials, you have to think about how much this specific raw material will contribute to a developing fire and how well does it fit my fire retardancy design approach for the product. This results in the design space, when compared to other coatings, being completely different.
Typically, we say the first and foremost parameter we must meet is a desired level for the fire performance. Without this, the coatings are not considered to be a fire retardant coating. Secondary, we start to match all the other requirements from a coatings point of view. At Teknos, fire retardant coatings are a high strategic area of interest and as part of this effort, we have established the fire retardant technology competence centre. We also have an advanced fire lab with state-of-the-art test capabilities in-house. Here we can evaluate our fire retardant coatings in relation to fire performance on test parameters which we must meet for the final SBI tests.
Why did you invest so much in this? Is this business getting more important?
Ravnsbæk: We do see a trend in construction to use more sustainable materials, with an additional high focus on aesthetically pleasing materials. Wood and wood-based substrates fit very well into this trend, however, as wood (like many other construction materials) is combustible, additional performance requirements are in place. The coating of wooden substrates has always been a core competence of Teknos, so this is a natural technology extension to our already extensive product portfolio. Our customers require complete solutions from their suppliers, even more so as the performance standards continue to add complexity and new levels of certification for them to meet. We see this as a natural extension of the development and support we offer to our customers and to the wider industry.
Can you say a bit on the current challenge in developing coatings that have a good reaction to fire performance?
Ravnsbæk: For the whole industry, it is currently a huge challenge to create transparent fire-retardant coatings with a good reaction to fire performance. The availability of raw materials which give fire performance is extremely limited. We do not have a large toolbox and to a large extent, the support by the raw materials suppliers is not as well established for fire retardant coatings as for traditional coatings.
By way of simplification, your classic coatings can be viewed as refined fossil fuels to feed the fire. In fire retardant coatings, we are not just trying to mitigate those properties, but to reverse their behaviour. If you take wood for example, this is accepted as a class D building material on a scale of A to F. Hence, if you coat it with a fire-retardant coating, you want to bring it up to a class B material, which is the best you can reach for a combustible construction material. Another challenge being, you typically use thin coatings at layers of 100-200 microns. If you compare with fire resistant coatings on the other hand, these typically use a few thousand microns. When you combine this with the fact a lot of the raw materials you traditionally add to your coating actually bring you in the wrong direction, this is a challenging task.
And how do you do that?
Ravnsbæk We try to minimise these fire contributions as much as we can and try to optimise the effect of the active fire-retardant ingredients. You can do it in a multitude of ways. We at Teknos work with what we call thin-film intumescence, where we borrow a bit of technology from fire resistance coatings. We then optimise it towards working at much lower film thicknesses and minimise as much of the contribution a substrate might have to a developing fire. Here, we are looking at barrier properties and other mechanisms.
I suppose you are also affected heavily by regulation when doing that. What does this specifically mean for fire retardant coatings?
Ravnsbæk: One of the biggest challenges for fire retardant and fire-resistant coatings is that these products are extremely expensive in third party testing. All the required documentation makes these products dependent on large upfront investments. This means you have to be even more careful when selecting materials which could end up being regulated. We have seen this with the restriction for halogenated fire retardants that came about ten years ago. In Europe, we now have nearly a complete ban of those. On the raw material level, it is necessary to stay on top of the trends to stay alive in this game.
One recent example is probably melamine, which is used within many fire-resistant and -retardant coatings. Just in August, Germany proposed a carcinogenic classification of melamine which could affect the market heavily.
Do you think this classification of melamine will become an actual regulation?
Ravnsbæk: I am not an environmental specialist. But if you look at the history of such proposals, the likelihood of such a proposal having an impact is much higher than going away without one. When a country proposes a classification change like this, they typically have some data backing their cause. The resulting effect is of course changes, although the classification may not be increased to the extent initially proposed, because the industry comes up with counter studies. But most of the time, there will be a change. A good example of this is probably the case of titanium dioxide.
The interview was conducted by Jan Gesthuizen
The latest trends, innovations and developments on fire retardant coatings will be discussed at the European Coatings Fire Forum on 6-7 November in Madrid, Spain. Jens Ravnsbæk will be one of the speakers and talk about the reaction to fire of coatings.
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