FINISHING VIEWPOINT: The Great Powder-on-Wood Debate
Powder coating on wood - so what’s it going to be, ultraviolet (UV) curable or thermoset? In my travels over the last couple of months, I’ve encountered this issue more than a few times.
Powder coating on wood - so what’s it going to be, ultraviolet (UV) curable or thermoset? In my travels over the last couple of months, I’ve encountered this issue more than a few times.
A little over 10 years ago, technologists heralded the emergence of an innovation that would open a huge untapped market for the then maturing powder coating industry. What they had claimed was a new finishing approach that would allow heat sensitive substrates such as composite boards, plastics and assembled goods to benefit from the advantages of powder coating.
The breakthrough involved the dovetailing of materials and application technology development. Chemists had found a way to synthesize powders based on UV cure technology. The advantage of UV powders was the ability to separate the cure mechanism from the heat needed to manufacture and apply the powder. It could melt to a low viscosity, creating a very smooth finish before the cure mechanism was initiated by exposure to UV light. Curing was quick, taking only a few seconds of direct contact with high-intensity UV energy.
Paralleling this advancement in chemistry was novel equipment technology that made the application of powder to marginally conductive substrates like composite boards much more feasible. The powder application equipment folks designed tribo-charging systems that were better suited to evenly applying powder on wood. Oven and conveyor engineers created turnkey systems capable of preheating boards before powder application and subsequently melting and UV curing the finish.
Since the advent of UV curable powder coating, technologists developed another means to apply powder on wood. Chemists synthesized low-temperature curing resins possessing acceptable storage stability while still maintaining good flow. These systems are stable during powder manufacture but can cure at 240 to 250°F. The more stable resins and faster catalysts gave the chemists the tools to formulate powders that could be used on boards and plastics without the addition of a UV curing process.
In spite of all this remarkable technology, the market did not explode as some had predicted. A few pioneers dabbled in powder on wood, and there remain a handful of lines producing powder coated wood products. But powder coating technology for wood has never taken off as expected.
This situation has opened the debate between the UV powder enthusiasts and the more conventional thermoset cure adherents. The UV products are more chemically resistant and can be processed at lower temperatures than the low-cure thermosets. However they are more costly and require the additional UV processing step. Thermosetting low-cure powders can be successfully applied to composite boards, but they are not quite as tough as their UV counterparts.
This month we bring you an insightful analysis of the powder-on-wood phenomenon authored by Dr. B.P. Mallik of Asian Paints (see pp. 34-39). We hope you find this article and the rest of this issue informative and useful. Please let us know how you feel about this or any other emerging issue in the finishing industry.
Powder coating on wood - so what’s it going to be, ultraviolet (UV) curable or thermoset? In my travels over the last couple of months, I’ve encountered this issue more than a few times.
A little over 10 years ago, technologists heralded the emergence of an innovation that would open a huge untapped market for the then maturing powder coating industry. What they had claimed was a new finishing approach that would allow heat sensitive substrates such as composite boards, plastics and assembled goods to benefit from the advantages of powder coating.
The breakthrough involved the dovetailing of materials and application technology development. Chemists had found a way to synthesize powders based on UV cure technology. The advantage of UV powders was the ability to separate the cure mechanism from the heat needed to manufacture and apply the powder. It could melt to a low viscosity, creating a very smooth finish before the cure mechanism was initiated by exposure to UV light. Curing was quick, taking only a few seconds of direct contact with high-intensity UV energy.
Paralleling this advancement in chemistry was novel equipment technology that made the application of powder to marginally conductive substrates like composite boards much more feasible. The powder application equipment folks designed tribo-charging systems that were better suited to evenly applying powder on wood. Oven and conveyor engineers created turnkey systems capable of preheating boards before powder application and subsequently melting and UV curing the finish.
Since the advent of UV curable powder coating, technologists developed another means to apply powder on wood. Chemists synthesized low-temperature curing resins possessing acceptable storage stability while still maintaining good flow. These systems are stable during powder manufacture but can cure at 240 to 250°F. The more stable resins and faster catalysts gave the chemists the tools to formulate powders that could be used on boards and plastics without the addition of a UV curing process.
In spite of all this remarkable technology, the market did not explode as some had predicted. A few pioneers dabbled in powder on wood, and there remain a handful of lines producing powder coated wood products. But powder coating technology for wood has never taken off as expected.
This situation has opened the debate between the UV powder enthusiasts and the more conventional thermoset cure adherents. The UV products are more chemically resistant and can be processed at lower temperatures than the low-cure thermosets. However they are more costly and require the additional UV processing step. Thermosetting low-cure powders can be successfully applied to composite boards, but they are not quite as tough as their UV counterparts.
This month we bring you an insightful analysis of the powder-on-wood phenomenon authored by Dr. B.P. Mallik of Asian Paints (see pp. 34-39). We hope you find this article and the rest of this issue informative and useful. Please let us know how you feel about this or any other emerging issue in the finishing industry.
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