Powder Coatings are in Full Swing at the Playground

Low-temperature-curable powder coatings are often touted as the next generation of coating technology due to their environmentally inoffensive list of ingredients, Outdoor playground equipment ought to be bright, cheerful, and stimulating as well as creative, inclusive, and durable wherever it is present for children at schools, daycares, parks, churches, shopping malls, and churches. At the same time, playset manufacturers deserve high-quality, efficient, sustainable, and economical coating technology to meet their customers’ needs. Powder coating formulators have been delivering these goods to all players for decades and continue to do so, even when the trends in playground equipment design and children’s needs have shifted over the years.

A modern focus on incorporating sensory elements into playground equipment using sustainable materials such as recycled plastics and rubber, integrating technology for interactive play, and adding climbing structures and obstacle courses, has pushed powder coating developers to do some reformulations. However, powder coatings, by their nature, complement many of today’s playground trends. Continual use of powder coatings in this market have only contributed to creating the highest quality play equipment while prioritizing children’s safety and accessibility needs.

Playing with Powder is the Right Choice

Playground equipment manufacturers were some of the first to adopt the transition from solventborne paint to powder coatings. The mid-1970s heralded the first use of thermoset powder to coat consumer-grade swing sets, which involved an outdoor-durable polyester used to finish their frames. Since then, a palette of endless colors, along with durability, environmental benefits, and the attractive economics of powder coatings have provided a tough and appealing finish for commercial playground equipment.

Besides the obvious environmental advantages due to the elimination of solvent emissions and the economics of a coating material that enables the overspray to be captured and reused, powder coatings bring much more to the party. Many playground equipment manufacturers have been able to eliminate the use of costly substrates such as galvanized steel and some stainless steel components because of the powder’s excellent corrosion resistance. In addition, far fewer parts are rejected since relatively thick powder coating films can be applied without runs, sags, or solvent popping.

Recent Developments

The trend of creating playgrounds that are sensory-rich with sustainable and safe materials is no obstacle for powder coating manufacturers. For instance, “Gator Grip” non-slip products based on polyethylene (PE) thermoset chemistry have been formulated as well as vibrant colors and special-effect powder coatings that generate visually appealing finishes.

The goal of using sustainable materials coincides with the eco-friendly features of powder coatings. Highly durable powder coating systems extend the longevity of these playground centers, which significantly reduces the need to prematurely replace equipment. Also, powder coatings already have a minimal environmental footprint and are relatively non-toxic.

Antimicrobial powder coatings are emerging as a preferred material for some playgroup equipment manufacturers. Offering a coated surface that thwarts bacterial and germ growth enhances the hygiene and safety of children.

Meeting Stringent Requirements

Commercial playground equipment’s life expectancy is a minimum of 10 years. This equipment not only requires the UV durability of an architectural coating, but also durability from regular use by energetic youngsters. The coating must exhibit high abrasion, chip and impact resistance. Typically constructed using mild steel, these playsets also require a robust coating system to prevent corrosion, especially in coastal and salt-laden environments.

Meeting these demanding specifications necessitates a robust coating system that starts with quality substrates, followed by substrate preparation, the coating material application process and finally, curing.

If oxides or weld spatter are present on the metal substrate, abrasive blasting removes these contaminants prior to powder coating. The next step is a three- to five-stage metal pretreatment process, which removes residual oil and dirt contaminants and creates a chemical anchor for the coating to adhere to the steel. The metal pretreatment is dried in a forced air oven, then the clean parts are conveyed to the powder application system.

Four Main Coating System Options

Depending on the end user (consumer or commercial), warranty, and climate, four main high-performance powder coating options are available to meet playground equipment specifications (see Table 1). The simplest powder coating system is a single-coat outdoor-durable polyester powder used for entry-level consumer playsets. This quality will exhibit modest color fade and gloss loss after about two years of exposure in a non-coastal environment. Minor corrosion can occur on edges and where the coating may have been breached during installation or use.

A higher performance finishing system, expected to withstand 5-10 years in the field, uses a prime-topcoat combination. The primer commonly used is based on epoxy polymer technology that has been infused with a high loading of pigmentary zinc. A thick film of this powder is applied to parts and then gelled in an oven. The coating is only partially cured, then the still-warm part is topcoated with a “superdurable” polyester powder. Superdurable refers to the polymeric composition of the polyester resin used in these formulations. This chemistry enables up to five years of durability in the Florida climate before the coating begins to show signs of gloss loss.

A robust three-layer coating system is used to meet the performance required for the most extreme environments best described in ISO 12944-5 Corrosion protection of steel structures by protective paint systems. Playground equipment destined for environments designated in ISO 12944-5 categories C4 (coastal areas with moderate salinity) and C5M (coastal areas with high salinity) are coated with a zinc-rich powder primer followed by an intermediate barrier primer and top coated with a superdurable polyester.

Highly trafficked components such as decks and stairs on playground equipment are commonly coated with a textured thermoplastic polyethylene PE powder coating. This technology provides a combination of toughness, adhesion, and UV durability. The PE powder is typically applied using a fluidized bed technique. The fluidization is generated by passing clean, ambient-temperature air through a permeable membrane. This controlled air pressure causes the bulk powder to displace and gently churn. The process looks like a cauldron of boiling broth to the unsuspecting onlooker.

Clean, preheated parts are lowered into a bed of fluidized colored PE particles. The warm part enables the particles to deposit on the surface. Coated parts are then baked at a temperature above the melting point of the PE powder to ensure adhesion to the steel and an even, coarse-textured film.

In the past, a polyvinyl chloride (PVC)-based powder was used for these components. However, concerns about the potential toxicity of PVC prompted most manufacturers to replace it with a safer coating technology. Clever formulators developed non-toxic PE powder technology, which is available in a spectrum of colors and surface profiles, including a non-skid texture. Powder coatings are generally non-toxic compared to solventborne paints.

Ideal Balance of Properties

Using powder coatings to finish playground equipment is another example of how performance, diverse color palettes, environmentally friendly features, and attractive economics converge to benefit manufacturers, consumers, and the planet.

To learn more, reach out to the author at kbiller@chemquest.com or visit https://chemquest.com/cqpcr.

Read in Products Finishing.