The Advantages of Cold-Applied Polyurethane HFS

There are several technologies available for the installation of High-Friction Surfacing, including polyurethane (PU), methyl methacrylate (MMA), epoxy and thermoplastic hot-applied systems. While each technology has its place, cold-applied, moisture-tolerant polyurethane offers a particularly strong combination of performance, installation reliability, safety and environmental benefits.

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Unlike thermoplastic HFS, StarPolymers HFS does not require the binder and aggregate to be heated to extremely high temperatures before or during installation. Instead, the components chemically react and cure at ambient temperature, bonding the high-friction aggregate securely to the road surface.

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This fundamentally different approach brings significant advantages.

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Moisture Tolerance – Designed for the UK Climate

One of the most important characteristics of StarPolymers HFS is its moisture tolerance.

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The British climate can make road-surfacing applications particularly challenging. Substrates may retain residual moisture even when the surface appears dry, while rapidly changing weather conditions can make achieving and maintaining ideal application conditions difficult.

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Some resin technologies such as MMA and Epoxy, can be particularly sensitive to substrate moisture, increasing the potential for poor adhesion, blistering or premature failure if conditions are not ideal.

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StarPolymers HFS was specifically formulated to provide excellent tolerance to damp substrates.  Moisture tolerance, including frost, is one of the system's key characteristics and this makes StarPolymers HFS less prone to failure resulting from the vagaries of the UK climate.

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The system can also be applied to various substrates including concrete, bitumen, asphalt, wood and steel without requiring a separate primer and is capable of curing at very low ambient temperatures.

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For contractors, this provides a considerably more forgiving installation system and can reduce the risk of an otherwise correctly installed HFS system being compromised by common but less-than-perfect environmental conditions.

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Cold Applied – No 200–300°C Installation Process

The difference between cold-applied PU and traditional thermoplastic HFS becomes particularly significant when the installation processes are compared.

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Thermoplastic hot-melt systems are solid at ambient temperature and must be heated to approximately 200–300°C using gas-fired equipment before they can be applied. ​StarPolymers HFS requires no such heating.

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The three resin components are mixed together at ambient temperature, spread onto the prepared road surface and the calcined bauxite aggregate is broadcast into the uncured resin. The only significant installation energy identified is the small amount required to operate a mixer for approximately two minutes.

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Removing the requirement to maintain tonnes of surfacing material at hundreds of degrees Celsius also removes an inherently energy-intensive stage from the installation process.

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It additionally avoids deliberately placing material at approximately 200–300°C directly onto the existing highway surface. This eliminates the thermal shock associated with hot-applied HFS and the potential for excessive application temperatures to adversely affect heat-sensitive bituminous substrates.

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Significantly Lower Carbon Footprint

Perhaps the most compelling environmental advantage is demonstrated by an independent Carbon Footprint Review undertaken by Groundwork Pennine Lancashire, funded through the ENWORKS Improving Your Resource Efficiency Programme.

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The study directly compared StarPolymers HFS with a conventional thermoplastic Hot Melt HFS system and considered the materials and energy associated with producing and installing one square metre of each system.

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The difference was substantial:

HFS System Estimated Carbon Impact

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          StarPolymers HFS Cold Mix0.7574 kg CO₂e/m²

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          Thermoplastic Hot Melt2.4358 kg CO₂e/m²

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Within the scope of the study, StarPolymers HFS produced approximately 31% of the carbon impact of the thermoplastic alternative – in other words, the calculated carbon impact of the conventional Hot Melt system was more than three times greater.

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Put another way, the assessment indicates an approximately 69% reduction in the measured carbon impact per square meter compared with the Hot Melt alternative.

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Why Is the Difference So Large?

It isn't simply the energy required to heat the product on the roadside.​ The assessment identified several important differences between the systems.

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Both systems were assumed to use approximately 2 kg of binder per square metre, but StarPolymers HFS uses a net 6 kg of aggregate per square metre compared with 10 kg for the Hot Melt system. Excess aggregate from the cold-applied installation is swept up and reused on subsequent applications.

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That represents 40% less aggregate consumption per square metre, reducing the carbon associated with extraction, calcination and international transportation of the calcined bauxite.

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The thermoplastic system also requires energy to heat and combine the resin and aggregate during manufacture and then additional LPG energy at the installation site to return the material to its application temperature.

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By contrast, StarPolymers HFS is a reactive cold-cure system. The report notes that the only energy required during laying is the generator used to mix the resin components, with mixing taking no more than approximately two minutes.

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The result is a fundamentally less energy-intensive method of producing a high-friction road surface.

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Cold applied PU, MMA and Epoxy

Cold application alone does not make every resin system equal so why cold-applied Polyurethane?

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Different High-Friction Surfacing technologies bring different compromises. Traditional thermoplastic systems require extremely high manufacturing and application temperatures; MMA systems can have poor moisture tollerance, introduce highly flammable reactive monomers and, in some systems, organic-peroxide catalysts carrying serious fire and explosion warnings; while older epoxy technologies can present their own handling, odour, performance and application limitations.

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StarPolymers HFS takes a different approach. Its cold-applied polyurethane technology is solvent-free, ultra-low VOC, non-flammable, moisture tolerant and capable of curing at low ambient temperatures. It requires no application temperatures of 200–300°C and, on typical substrates, does not require a separate primer. Its tolerance of damp substrates is particularly valuable in the unpredictable UK climate, reducing one of the major variables capable of compromising resin-to-road adhesion.

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Cold application also produces a substantial environmental advantage. An independent Carbon Footprint Review calculated an impact of 0.7574 kg CO₂e/m² for StarPolymers HFS compared with 2.4358 kg CO₂e/m² for the thermoplastic Hot Melt alternative. The study found that StarPolymers therefore produced approximately 69% less carbon impact per square meter.

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The result is an HFS technology that combines the rapid installation and high performance required for highway applications with greater moisture tolerance, low-temperature application, reduced energy consumption and a significantly lower calculated carbon footprint than traditional Hot Melt technology.

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A More Sustainable Approach to High-Friction Surfacing

High-Friction Surfacing is installed primarily to improve road safety, but the technology used to achieve that performance can have a significant effect on the environmental impact of the installation.

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StarPolymers HFS demonstrates that exceptional road-surface performance does not have to depend upon energy-intensive hot-applied technology.

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By combining cold application, moisture tolerance, reduced aggregate consumption, very low installation energy requirements and BBA HAPAS-certified performance, StarPolymers HFS provides a modern alternative to traditional thermoplastic, MMA and epoxy technologies.

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Most significantly, its environmental advantage is not based solely on theoretical claims. An independent comparative assessment concluded that, within the scope of the study, the carbon impact of StarPolymers HFS was more than three times lower than that of the traditional thermoplastic Hot Melt alternative.​