Traffic paints must stay stable until it’s time to dry — very, very quickly. Here’s how they do it

Fast-drying? Check. High performance? Check. Low-VOC, APEO-free and good stability? Check, check, check.

For formulators in the traffic paint industry, it’s not quite as simple as ticking boxes, but there’s always pressure to add benefits and improve performance. Coating technology must evolve to anticipate changing demands, delivering everything the paint formulator needs in one tidy package.

From a chemistry standpoint, that can be tricky: when you add some of the required performance characteristics, it becomes more difficult to achieve others. Fast-drying properties, for example, are often at odds with stability.

Traffic paints created with ACRONAL® Xpress 4347 help waterborne traffic paint formulators make those checkmarks without sacrificing any key attributes.

The challenge of competing attributes

Traffic paint delineates travel lanes on roads and highways, parking spaces and loading zones — all of which play an important role in maintaining road safety. One of the industry’s primary goals is to minimize slowdowns and disruptions in traffic. The faster a paint dries, the sooner cars can get back on the road.

Armin Burghart, Senior Scientist of Product Development at BASF, says the fast-drying attribute is critical in the field, but faster drying time can jeopardize the stability of a formulation.

“The chemistry of the fast-drying aspect conflicts with stability. The two properties need to be balanced,” he says, adding that a stable paint should maintain its liquid form whether it’s in storage or out in the field. “The end user needs a stable paint, not one that will thicken or gel prematurely.”

Fast-drying is governed by the crosslinking mechanism. Once the paint is applied on the road, the crosslinking kicks in and it starts to dry quickly.

“Chemically, that’s the main challenge — we don’t want crosslinking to happen in the paint can or the pail,” Burghart explains. “We have to suppress crosslinking while the paint is in a liquid state, then speed it up once it’s been put down on the road.”

With that precise timing in mind, Burghart’s team created ACRONAL Xpress 4347 to help traffic paints dry quickly and remain very stable.

A history of crosslinking precision

ACRONAL Xpress 4347, an all-acrylic copolymer, comes from a line of proven latex technologies developed by BASF.

“We have a strong knowledge of the science behind long-lasting pavement markings, as well as an extensive portfolio of water-based latex polymers and formulation additives,” says Antonia Chan, Marketing Manager of Construction Solutions at BASF.

ACRONAL Xpress 4347 is based on BASF’s proven QUICK-TRIGGER® technology. The broad family of products that use QUICK-TRIGGER technology addresses a variety of issues outside the pavement marking sphere, including early rain resistance in architectural coatings and roof coatings, concrete curing compounds and fast-drying seal coats in construction.

Tested on the shelf and in the field

Because performance is so crucial and the process so precise, BASF chemists emphasize the need to test paints for the wide array of conditions they’ll face in the end user’s hands.

“Anything we do in the lab is supposed to simulate field conditions,” Burghart explains.

For fast-drying, BASF uses a “dry no-pick up” test — an official ASTM method (ASTM D 711) that simulates car tires running over freshly-applied road paint. The lab paints a small-scale traffic lane with the coating, then uses a heavy rubber wheel to recreate the effect of a tire running over the lane. Traffic paints formulated with ACRONAL Xpress 4347 have achieved dry no-pick up times of 4 minutes and 30 seconds, exceeding the 10-minute dry no-pick up time criteria to pass the test.

Fast-drying is also tested in the field.

“The field test consists of a dry no-track time where a car drives over a freshly painted traffic stripe after a certain period of time. BASF matched 60 seconds of dry no-track time during the National Transportation Products Evaluation Program (NTPEP) in Florida,” says Chan. “That means 60 seconds after application, cars could start driving over markings without tracking paint all over the road.”

That’s a competitive drying speed that reduces road closure time significantly, but the stability testing is what sets ACRONAL Xpress 4347 apart from other products.

“We test the paint stability in two ways: freeze-thaw stability and oven stability, which simulates the conditions of paint storage,” Burghart explains.

“We’ve seen that some commercial products dry quickly but can’t withstand the stability testing. Commercial paints would set in the can, whereas paints formulated with ACRONAL Xpress 4347 would pass several cycles of heat or freeze-thaw stability testing,” Chan explains.

Finding the full package

Aside from fast-drying and stability, durability is a key component of a high-performing traffic paint. End users want paints that last longer on the road before they need to be re-applied, allowing them to maintain safe road conditions for longer stretches of time.

“From a product design standpoint, we keep a close eye on the material compatibility between our polymer binder and other paint ingredients,” Burghart says. “That’s a big part of adding durability to the end product.”

To that end, BASF regularly consults with customers to ensure all constituents of the formulation are compatible. They also offer technical assistance to meet low-VOC and APEO-free requirements. All those factors combined allow traffic paint formulators to deliver long-lasting markings, fewer delays on the road and less wasted paint on the end user’s shelf.

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