The process and advantages of UV curing powder, just read this article

UV curable powder coatings shorten the processing time of MDF

Author: Laura Copeland (Lara Copeland), contributing author, "UV + EB Technology" magazine

Compiler: Du Peng Runao Chemical

Keywords: UV curing powder coating MDF medium density fiberboard wood

The two companies, Keyland Polymers and DVUV, also located in Cleveland, Ohio and occupying adjacent buildings, have found ways to collaborate far beyond their spatial proximity.
As an innovator of UV-curable powder coatings applied to medium density fiberboard (MDF), DVUV focuses on custom powder coating components or parts for retail, store fixtures, POP displays, healthcare, education, and office furniture industries.

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This manufacturer of medium to high volume products with automated production lines also provides finished components for fixtures/displays, countertops, shelves, wall panels, cabinets and signs.

Keyland Polymers develops, formulates, manufactures and sells UV-curable powder coatings to DVUV and other customers who coat MDF and substrates including plastics, composites, metals and other materials.

Rebecca Lonczak, Marketing Manager of DVUV/Keyland Polymers, explained that DVUV does not paint natural wood, but only applies to MDF substrates.
Because the wood particles, density and moisture content of the latter are uniform.

"MDF is easy to process and has a uniform and homogeneous surface.
Natural wood can also be painted with powder coatings, but the finish may be uneven.
Due to changes in resin and moisture content in natural wood, outgassing and pinholes may occur Problem," Rebecca said.

The density, fiber, resin, and moisture content of natural wood vary depending on the type of wood.
In addition, it also has the influence of where it grows.

Even if the tree species is the same, each tree is different.

Since the powder coating process uses heat to melt the powder, even at lower temperatures and short exposure times, heat can cause uncontrollable reactions in natural wood.
This makes it particularly problematic to achieve a uniform surface when powder coatings are applied to natural wood.

The UV-curable powder coating of MDF produces a more consistent, visually pleasing surface .

Keyland polymers produce UV-curable powder coatings by combining resins, pigments, high-performance additives and photoinitiators .
Photoinitiators are the key components.

They absorb high-intensity ultraviolet rays, generate and activate free radicals to crosslink the coating.

Additives enhance the coating surface by improving or adjusting specific properties-scratch or abrasion resistance, gloss and texture.
Pigments produce color and opacity.

UV-curing powder coatings are produced in the same way as thermosetting powder coatings, and the equipment used is also the same-the process includes mixing, extrusion, cooling, slicing, grinding, grading, sieving and packaging.

In order to achieve a good curing effect, it is necessary to match the type and amount of photoinitiator with the ultraviolet light source, including the proper combination of ultraviolet energy dosage, intensity and wavelength.

There are several types of medium pressure mercury vapor UV lamps that can be used for UV curing of powder coatings.
The mercury lamp ("H" lamp) provides short-wavelength (220-320nm) ultraviolet energy, suitable for varnish and transparent paint applications.

Iron-doped mercury lamps ("D" lamps) provide longer wavelengths (320-400nm) of energy, which aids the curing of systems with low pigment content.

MDF initial workpiece is UV cured during powder coating

The technological process of DVUV ultraviolet curing powder coating is very fast.
Lonchak explained: "This is a 20-minute single-step process .

The initial MDF workpiece can be turned into a finished workpiece, which can then be packaged and shipped at any time.

First, the workpiece is suspended on the production line, and compressed air is sprayed to remove dust particles remaining in the processing process.
Surface sanding is usually no longer required before powder coating.

Next, the MDF workpiece enters the low-temperature preheating oven for one minute.

Then, use the automatic spray gun system to electrostatically coat the UV-curing powder coating.
Then melt or gel the powder in a low-temperature oven for one minute.

Once melted, the workpiece will immediately solidify under UV light irradiation.

Ultraviolet curing powder coatings were developed more than 20 years ago as a substitute for thermal curing powder coatings.
Thermal curing requires high temperature (about 400°F/204°C) and takes 10-30 minutes or more to complete.
The processing time is longer, and additional cooling time is required before the next operation processing.

As Ronchak pointed out, the main advantages of UV curing over thermal curing are in terms of time and temperature .
The electrostatic powder coating process of UV curing powder coating and thermal curing powder coating is exactly the same.
However, the melting/flowing and curing process are important different features that distinguish the two functionally.

The UV curing process is completed instantaneously .
Before UV curing, it only needs a short one-minute preheating at a temperature of 220-240°F (104-116°C) to melt/level the powder coating.
This gives it the advantages of significantly shortening the process time and lowering the overall temperature, making the UV-curing powder coating process very important in MDF manufacturing.
"Excessive heating and exposure time may lead to cracking of the sheet and other defects," Lonchak points out.

Powder coatings have brought some challenges, but DVUV has mastered the measures and means to overcome these challenges.
Changes in humidity and temperature will affect the success of the process, but the process control operation in a temperature-adjustable factory makes this problem easy to deal with.
The humidifier ensures that the MDF board maintains the correct moisture content before powder coating .

DVUV's parameter setting and testing during the first run also ensured stable and consistent products.
DVUV's operation of each link is customized according to the customer's parameter requirements for the workpiece.
Lonchak concluded: "Line speed, spray gun distance and processing temperature are different and corrected for every project we run.

In addition to checking during operation to ensure quality, the production team also set up trial operation steps.
The quality control of finished parts includes a series of destructive and non-destructive tests:

• Compare the surface of the workpiece with the standard part for visual inspection

• Trafigura thickness gauge test (measuring coating thickness)

• Gloss reading

• MEK solvent resistance test

　"Our production team also has preventive maintenance, traceability analysis and corrective action plans when quality or process problems occur.
"

The future of DVUV powder coating MDF is bright.
The government and regulatory agencies are restricting or eliminating the use of solvent-based liquid coatings.

Water-based liquid coatings are difficult to use on MDF, which makes UV-curable powder coatings an ideal processing solution for MDF.

UV-curable powder coatings are solvent-free, non-toxic, and contain no volatile organic compounds (VOC) or harmful air pollutants.
No special permission is required for production operations.

DVUV is witnessing an increase in demand from manufacturers of furniture and MDF components, and these manufacturers are seeking a reliable supplier of high-quality, environmentally friendly and cost-effective finished MDF components.