Films as thin as a few microns can be achieved
Less material means lower costs. Naturally it seems that lowering the film thickness of a coatings is always a desirable target. “Fully coherent powder coating films as thin as 20-30 μm have been achieved on commercial application lines” explains Nigel Sherwing who works as Technical Director at Akzo Nobel.
And even more is possible: “In theory, films as thin as a few microns can be achieved with powders.” However, he sees some challenges for that. As does Robert Watson, Global Marketing Manager for Powder Coatings Resins at Allnex.
Thin powder coatings can have downsides
Nigel Sherwing is Technical Director Powder Coatings at Akzo Nobel
“Lower film thicknesses have a greater tendency to show increased orange peel, and additionally hiding power is reduced, especially in lighter shades and coatings with organic pigmentation”, explains Watson. He also sees the risk of reduced protective properties: “Lower film thickness can negatively impact edge coverage which can lead to a higher risk of corrosion.”
Robert Watson is the Global Marketing Manager Powder Coating Resins at Allnex
Both experts also agree that the need and handling of thinner particles are a challenge. “You have to take into consideration, that you need finer grinding to reduce particle size distribution in order to achieve a thin powder coating layer”, explains Robert Watson from Allnex. Nigel Sherwig of Akzo adds that particles must be fluidised, transported through tubing without blocking, sprayed, and any overspray recycled to improve customer economics. “These processes become harder as the particle size reduces”, he says.
More trends for powder coatings
Aside from film thickness the powder coatings market is also influenced by numerous other trends. Digitisation is one of the most important ones, at least for Nigel Sherwing. “E-commerce, colour digitization and digital tools are a key area of development”, he says and adds “We have already rolled out several digital apps across different market segments supported a highly accurate colour-measurement tool that pairs with mobile software to allow fast and accurate color selection whilst on the go.”
For Robert Watson lower and faster curing temperatures are a key trend. Temperatures of 130 °C and lower “allow greater access to temperature sensitive substrates, whether wood, composites or plastics. This will become more and more important as innovative material combinations are used for construction and fabrication.” Also both experts agree that needs from the wide field of sustainability will influence the development of powder coatings.
You will find more about this and longer detailed explanations about film thickness in the original interview that was published in European Coatings Journal 12/2018. It is available onbline for subscribers of our digital library European Coatings 360°