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How to Powder Coat MDF

Powder coating MDF – why and how?

If you know powder coatings, you know it is designed for protecting and decorating metals, like aluminium and steel.  Back in the late 90’s the industry started experimenting with powder coating other materials like MDF for furniture and kitchen cabinetry.  While the early days of the technology development didn’t exactly go to plan, the time since has been used to perfect the process.

Why powder coat MDF in the first place? Initially the idea was to offer a more sustainable alternative to solvent based paints and PVC foils for furniture and cabinetry made from MDF. Providing a highly durable, attractive furniture product without the environmental impact. While that’s still true, the limitations of powder on MDF meant the technology didn’t get much of a foothold in the market. Today however, the technology challenges are largely solved and breadth of finishes possible continues to evolve.  Which means powder can play a part in improving the manufacturing industries sustainability footprint by lowering carbon emissions, improving air quality, reducing waste, minimising water use and using materials that can be recycled or re-used.

Powder coating MDF process.  The process relies on low cure powder formulations that melt, flow and cure as fast as possible to minimise edge cracking, dehydration and off-gassing of the MDF.  These powders are available from a range of producers that claim 130c for 3-5 minutes to 140-160c for 5-7 minutes, when cured in an infra-red oven. Powders that cure when exposed to UV light are also available and reduce the cure temperate window to as low as 100c but they require the addition of UV lamps to get the job done.

The electrostatic application of the powder utilises the moisture in the board (ideally 4-8%) to attract the charged powder. Like in metal coating, the substrate needs to be cleanly grounded. The board is lightly pre-heated to around 60c, which helps draw the moisture to the surface and then the powder is applied. Managing film thickness and consistency, particularly on the edges of the MDF, is key to avoid blistering during cure, thick edges and appearance inconsistency. This can be controlled with the use of counter electrodes in the coating booth, positioned opposite the powder applicators, they help prevent a buildup of powder on the edges by drawing excess powder spray away from the part.

The melt, flow and cure the powder is best achieved with infra-red, which is an effective and efficient heating technology.  The right wavelength of IR will ensure optimal absorption by the coating and less by the substrate, minimising the impact of high temperatures on the MDF while maximising cure. Ensuring a consistent and even heat profile of the MDF by placement of the IR heaters and reflection of the IR is also key to consistency.  IR can be electric or gas powered depending on the degree of surface temperature control required, access to natural gas and energy costs.

Climate Surfaces has been coating MDF for 25 years, not without its challenges.  Back in 2004 we pioneered and patented a two-coat process to address some of the shortcomings of the technology. These days the business powder coats MDF panels on a large format horizontal powder coating line. The panels are cut then have an edge tape applied to the edges, just like a joiner or shopfitter would do when working with low pressure melamine panels.  Because powder can be produced in any colour for a small minimum order quantity compared to laminates and the colour doesn’t change over time, has meant we’ve supplied a leading NZ supermarket for over a decade. Always the same colour and quality, no colour deletions.

There is a smattering of powder applicators and OEMs around the world that have purpose built coating lines for kitchen cabinetry, furniture or anything where powder can play a part in finishing MDF.  Each company has carved out a niche for powder, sometimes on other substrates like plywood or plasterboard.  There is still some way to go before powder can rival the incumbent technologies of paint, laminates and foils but it is moving in the right direction in terms of finish options and production formats that can reduce costs.

What’s next for powder coating MDF?  Covestro, a leading resin producer for powder coatings, has developed a process called ImFuse®, which combines a fast curing, low bake powder with a hot press curing technique. This enables smooth and high gloss finishes, as well as designs to be imprinted into the coating, giving it a visible structure that can replicate other materials like wood. Powder is also a great base to digital printing onto with any image or design. The end result can replicate other materials or add unique finishes.

Powder coating technology on non-metallic substrates like MDF will continue to find its way into the market as long as there are companies willing to innovate with a very sustainable coating technology.  The world needs a dry and efficient coating technology to ensure materials look great and last longer with less impact on the planet and people.