One for the road

C&I Issue 8, 2008

In a small corner of France, in the foot-hills of the southern Alps, French car drivers are unwittingly helping to improve road safety. White stripes painted across the road in the town of Carros are made with the latest state-of-the-art road paints incorporating Rohm and Haas’ acrylic resin binder Fastrack. As drivers roll over these white lines, they are performing a rigorous test of the paints’ durability and strength. The theory is that road markings improve visibility and the more durable they are, the longer the road is maintained safely. Thus longer lasting road markings should help to lower maintenance costs and at the same time save lives.

In the UK alone there were 258 000 road accidents in 2006, of which 3172 were fatal. Almost 50 000 of these accidents occurred at night with another 26 000 taking place in the wet. It is under these conditions that Rohm and Haas says that its binder, the glue that holds the traffic paints together, could make the biggest difference to road safety as paints made with it are more durable and maintain their reflectivity better.

Inadequate or masked signs or road markings were recorded as a contributory factor in 683 UK accidents last year. ‘Clear markings can help drivers,’ acknowledges Lorna Jackson of the UK road safety charity, Brake: ‘I think we all know how distracting it can be if you’re struggling to work out where you’re supposed to be or what the speed limit is while trying to drive.’

The development of the Fastrack binder began back in the late 1980s after Rohm and Haas had just entered the traffic paints market, says Andrew Trapani, the firm’s European technical director for paint and coatings materials. The company was trying to tackle a problem intrinsic to road paints that use water as a diluent. Water-borne road paints work well in warm, dry conditions, but once the weather becomes more humid or wetter they dry much slower. This can be a real headache for agencies charged with maintaining roads and keeping traffic moving because roads need to stay closed longer after a paint job in humid conditions.

‘Rohm and Haas came up with a water-based technology that can dry almost independent of humidity,’ Trapani says. But when tests started on paints developed with the Fastrack binder the researchers spotted something else. ‘We started to notice that the lines lasted longer and that they were holding the glass beads better.’

The improved durability of the paints is due to the composition of the binder. Comprising long chains of very high molecular weight polymethacrylates, paints formulated with Fastrack are more resistant to abrasion by the mechanical wear of tyres – the principal route by which road markings get damaged. The long polymethacrylate chains bind up the road paint’s glass beads, which are responsible for its reflectivity, more tightly and can therefore improve visibility at night. The high molecular weight of the acrylic particles also improves the paint’s UV stability, protecting it from sunlight degradation, and help it to resist water infiltration.

Paints formulated with Fastrack can set in humid conditions because the curing process, when the paint sets solid, does not rely on the evaporation of water — which is slowed in humid conditions — but on the pH of the paint. ‘The pH of freshly applied water-borne traffic paints will change over time with exposure to the environment,’ Trapani explains. ‘As the pH lowers it leads to solidification of the paint as the pigment and acrylic binder particles coagulate.’ In tests by official bodies and Rohm and Haas, paints with Fastrack lasted between 30 and 100% longer than solvent-borne paints.

George Lee, director of the Road Safety Markings Association, notes that the UK market for road markings is unusual in Europe as it is dominated by thermoplastics. In mainland Europe, paints are much more widely used. However, paints are beginning to find greater use in the UK, he notes, particularly for line refurbishment, where paints are over-sprayed onto thermoplastic road markings.

An estimated 40 000t/year of solvents were released into the atmosphere from road marking activities in the EU-15, according to Trapani. However, Rohm and Haas says that Fastrack paints emit only 11.6% of the volatile organic chemicals of solvent-borne road paints. Although the binder is formulated with a small amount of organic solvents, in the form of ethanol and Texanol ester alcohol (2,2,4-trimethyl-1,3-pentanediol monoisobutyrate), these are relatively environmentally benign. ‘Many solvent-borne traffic paints in Europe still use nasties like toluene,’ says Edward Appleton, manager of brand marketing and market research at Rohm and Haas.

Another feather in Fastrack’s cap is its smaller carbon footprint, the company claims. A 10-year life-cycle analysis commissioned by Rohm and Haas and the French road-marking company Prosign, based on a 1km paint strip, found that CO2 emissions were half those of solvent-borne paints. Less energy is required to produce the paint, fewer waste products are created and maintenance and re-painting is reduced because of the paints' increased durability.

While paints made with Fastrack are more expensive than their solvent-borne counterparts, this is offset by lower maintenance and disposal costs, Trapani says. ‘The cost of paint in a painting operation is small — 20% or less — and most of the costs are human resources and the operation of the trucks,’ he adds.

The market distribution of road paints in Europe, excluding thermoplastics, leans heavily toward solvent-borne paints, with 88% of the market share as opposed to 12% for water-borne paints. In the US, where the situation was almost identical to Europe 15 years ago, water-borne paints now hold 90% of the market share. ‘One of the challenges we have is getting Europe to engage in legislation on solvent-borne paints,’ Appleton says. Countries like Germany, Italy, Greece and Spain are still big solvent-borne users, although in Scandinavia, where legislation has been enacted, there is now little-to-no solvent-borne traffic paints.

But while the European market for water-borne paints may still be small, it is growing fast. Between 2002 and 2006 the water-borne road paints market in Europe grew 42%, compared with a sluggish 4% growth in solvent-borne paints. According to Trapani, the really big prizes are to be found in emerging economies. The Turkish government is currently considering legislation to encourage the use of water-borne traffic paints and new EU member states in Eastern Europe will need to upgrade their roads to meet EU standards. The biggest area for growth, however, is likely to be South East Asia where nearly all road paint is solvent-based. ‘The potential for growth in these countries is enormous,’ Trapani declares. ‘Rohm and Haas has several plants in both India and China and is ready to ramp up production to make as much binder as is needed.’

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