Focus on construction: PU intumescent coating with fast cure capabilities

04 December 2023

Historically, epoxy-based systems have dominated the intumescent coatings arena, accounting for more than half of global revenue in this field. Now, there is a new polyurethane-based technology on the scene that has advanced capabilities and the potential to change the status quo

Earlier this year, global chemical company Huntsman launched Polyresyst® IC6005 system – a new two-component polyurethane-based solution for the construction industry that can provide passive fire performance alongside unique fast cure properties. PPCJ spoke to Stefan Priemen, Technical Manager for Coatings at Huntsman, to find out more.

Taking up the story, Stefan said: “The popularity of intumescent coatings is rising. In 2021, the global market for these specialist coatings was valued at US$$1.12bn. This is projected to reach US$$1.94bn by 2030 at a compound annual growth rate (CAGR) of 5.67% from 2022 to 2030.1 Applications for intumescent coatings vary. The technology is widely used on external steel structures, where fire poses a risk – for example, on offshore platforms, where beams, columns, sections and trusses need protecting. Similarly, intumescent coatings are popular in industrial and domestic buildings. Applied to building fixtures, fittings and structural components such as lintels, rolled steel joists (RSJ) and I-beams, intumescent coatings can give occupants extra evacuation time during fire incidents. They can also give firefighters crucial additional minutes to carry out their duties.”

“As a provider of both epoxy- and polyurethane-based coatings, Huntsman is acutely aware that both chemistries have their advantages and disadvantages. When it comes to intumescent coatings, epoxy-based systems are well established. However, they can take a long time to cure, which presents challenges in a factory production setting. Knowing this, we were keen to develop a polyurethane-based intumescent technology to see what improvements we could deliver.”

Huntsman’s innovation team had clear goals for its intumescent polyurethane technology. It needed to be suitable for applying to multiple substrates; easy to apply – using existing equipment; and fast to cure, even at a low temperature.

After in-depth research and development, the team created Polyresyst® IC6005 system. Continuing, Stefan said: “Obviously, equipping the coating with passive fire protection properties was top of our development check list and we worked hard to ensure that Polyresyst®IC6005 system would perform robustly at high temperatures. As the graph below shows, when applied to a steel substrate, and exposed to a 1100º Celsius (C) flame, Polyresyst® IC6005 system will reach a maximum temperature of 250ºC after 30 minutes. This is in stark contrast to a steel substrate coated with a standard polyurethane coating, which would reach 400ºC in less than five minutes.”

Caption:Temperature evolution of back side of two steel substrates, one with Polyresyst® IC6005 and one with a standard polyurethane coating

Caption: Front side steel substrates with Polyresyst® IC6005 exposed to a 1100ºC flame

The heat insulating properties of Polyresyst® IC6005 system are further demonstrated in the thermograph below, which shows the result of a furnace test for fire resistance, conducted according to DIN 4102-8 – the German DIN norm to determine the fire protection properties of building materials.

The thermograph illustrates what happened in a laboratory to a 5mm metal plate, coated with Polyresyst® IC6005 system at 2.3mm and 4.5mm respectively. The red line shows the normal ISO 834 heating curve to which the oven is heated for conducting the test according to DIN 4102-8 – with the temperature reaching 550ºC after just a few minutes.

In contrast, the blue line shows that a metal substrate coated with 2.3 mm of Polyresyst® IC6005 system will heat up much more slowly – only reaching 550ºC after more than 70 minutes.

The numbers are even more impressive on the yellow line – with a 4.5mm thick Polyresyst® IC6005 system coating taking more than an hour and a half to reach a similar failure temperature.

Caption: Performance of a 5mm metal plate, coated with Polyresyst® IC6005 system at 2.3mm and 4.5mm respectively, exposed in a furnace heated according to ISO834

With the fire protection performance of Polyresyst® IC6005 system assured, Huntsman began developing other characteristics that would set the coating technology apart from the competition.

Easy to apply – to multiple substrates

Stefan continued: “Confident that Polyresyst® IC6005 system had the right passive fire performance properties, we wanted to ensure it could be used on various substrates, utilising established application methods. The resulting system can be spray applied using a two-component, high pressure machine and impingement mixing / spray gun. It can adhere well to metal surfaces such as steel as well as wood and composites.”

In addition, for ease of use, Huntsman formulated Polyresyst® IC6005 system so it can be applied without the use of primers.

Caption: A technician spraying Polyresyst® IC6005 on a flex foam substrate 

Quick to cure

Huntsman’s next step was to work on the coating’s curing speed. Elaborating, Stefan said: “As previously mentioned, one shortcoming with epoxy intumescent coatings is the time they need to cure. Typically, after spraying, epoxy-based intumescent coatings take up to a day to set – if left to their own devices. This can be reduced to hours with the use of a curing oven. However, in a busy environment – where time is money – that’s not practical. Waiting several hours while a coating dries in an energy-intensive oven, before you can apply another layer in a manufacturing environment, is inefficient on many levels.”

Polyresyst® IC6005 system helps to overcome this issue. It has built-in fast cure capabilities, meaning you can spray the coating and watch it dry in seconds. The coating can have a tack free time of just two seconds, meaning there is less dripping or sagging. This helps reduce waste. Crucially, with such a rapid cure, users can also spray additional layers more quickly. This has the potential to be a game changer in high throughput, automated manufacturing environments, with Polyresyst® IC6005 opening the door to potentially substantial time and money savings.

Caption: A technician spraying Polyresyst® IC6005 on cardboard

Caption: Polyresyst® IC6005 sprayed on cardboard, touch dry in just a few seconds

Additional layers of benefits

According to Huntsman, Polyresyst® IC6005 system also has other typical benefits. A 100% solids system – with no added solvents and low levels of volatile organic compounds – the coating typically has a lower impact on air quality, human health and environment. Polyresyst®IC6005 system can also be used at low temperatures. Even at temperatures below 0ºC, the system can retain its fast cure properties and form a tough and flexible layer. This contrasts with epoxy intumescent coatings that are susceptible to cold shock and become brittle below 0°C.

Commenting, Stefan said: “While our Polyresyst® IC6005 system was predominantly developed with the requirements of structures being sprayed in factory settings, the technology can also be applied in situ – outdoors on building and construction sites. Ensuring that the coating could be applied easily, regardless of temperature or humidity was crucial. This also makes Polyresyst® IC6005 system a good choice for use in the northern hemisphere where severe weather can sometimes restrict the use of coatings and delay projects.”

Caption: Polyresyst® IC6005 shown during an elongation test


The toughness and flexibility of Polyresyst® IC6005 system has been extensively tested. According to ASTM G154 (Standard Practice for Operating Fluorescent Ultraviolet (UV) Lamp Apparatus for Exposure of Materials), the system was successfully cycled between cold and warm and humid and dry conditions – with no decline in performance.

Concluding, Stefan said: “For many years, specifiers of intumescent coatings have had to work with slow-curing coatings. With Polyresyst® IC6005 we’ve created an intumescent coating that can dry in seconds, can deliver comparable levels of fire protection and very good mechanical performance. Plus, it’s flexible enough to be applied in all kinds of conditions.”

“In a world where fire safety remains a significant concern, and intumescent coatings are growing in popularity, this kind of progress will benefit everyone – further increasing the adoption of coatings that can help protect people and assets from the risks presented by fire.”

Huntsman is a member of the Polyurea Development Association Europe

To watch a video about Polyresyst® IC6005 system, go to:

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