Substrates

Because of the low curing temperatures, UV curable coatings can be used for temperature sensitive substrates: MDF, plastics and metal objects with temperature sensitive parts. The use of UV powder on MDF and metal substrates (pre-assembled) gives a very good result. These products are already used commercially. Some other substrates such as solid wood and glass are still difficult to coat with UV powder coatings. DSM is constantly improving the application of the coatings on different substrates.

MDF (Medium Density Fiberboard)
Currently the two most widely used finishing techniques for MDF are liquid coatings and overlays. Overlays are paper-based or melamine impregnated laminates and thermoplastic foils. UV powder coating offers good possibilities to replace these techniques.

MDF is very suitable as a substrate for UV powder coating due to its low porosity and homogeneous surface. For MDF with milled surfaces, the density of the surface is very important. Very good coating properties are generally obtained. The adhesion and hardness of the coating compare very well to solvent borne or liquid UV coating and the chemical resistance is even better. The absence of solvent makes the flow of UV powder coatings less optimal than obtained with liquid paints. However, since the DSM UV powder coating contains semi-crystalline components, the flow of this system is much better than obtained with complete amorphous systems.

Recently the first commercial application on MDF was started with a textured coating for TV and audio furniture. Several manufacturers have used UV powder coating in the last two years on large scale trials. In the furniture market expectations for UV powder coating are high. Manufactures are switching from particleboard or solid wood to MDF so the MDF market is growing rapidly. This increase can partly be described as the result of different MDF-specials. In the year 1999 the total production capacity was increased by 9.4% compared to 1998.

Solid Wood
For solid wood the application of UV powder coating is more complicated. Wood is not homogeneous and can only be cured at temperatures below 80°C. Because of degassing it has been very difficult to coat solid wood with UV curable powder.

Other Wood
Application of a coating on Particle Board and Soft board is still not perfect. These substrates contain too many volatile compounds and, as solid wood, do not have a homogenous surface. Probably further developments can make this application possible in the future.

Examples of clear and pigmented coatings on MDF

Pre-assembled parts
Nowadays powder coating is the most used technique to cure metal objects. Applications where it is impossible to heat the total object to 180°-200°C cannot be cured with conventional powder. For example, these are metal objects with temperature sensitive parts like wood, plastic, MDF, rubber, grease and oil. UV powder can be cured on these objects because of its lower process temperatures. The pre-assembled products can be coated in one step instead of coating different parts before assembling the product. The manufacturers will save a lot of time and money in this way.

UV powder coatings have recently been used for commercial applications on industrial electric motors and radiators. Both these metal substrates have heat sensitive parts.

An example of UV powder coating on pre-assembled metal

Can & Coil
Speed and the application of thin layers are important factors for application of a coating on metal cans & coil. With the standard electrostatic spraying application this is not possible. However with the recently developed Electro Magnetic Brush (EMB) technology it is possible to apply thin layers at a high speed.

Plastics
It is difficult to apply the powder particles on plastics with a regular electrostatic spraying application (tribo / corona). However with the use of special additives that promotes the electrostatic spraying, good results are obtained.

Paper
UV liquid coatings are now used as overprint varnishes on paper and paperboard. These can be applied in very thin layers (6-8µm). DSM has developed the Electro Magnetic Brush application technology (EMB), which enables the application of powder particles in a very thin layer on paper substrate at a high speed. In this way UV powder coating can be used as an overprint varnish on cardboard, full color digital printed-paper and for spot printing. For further information about commercial purposes please contact us.

Glass
Glass is difficult to coat because the material is not very suitable for electrostatic spray application. If the substrate is heated, it is possible to apply UV powder on these substrates. The powder particles adhere to the substrate by melting instead of electrostatics.
Although, some glass containers are now coated electrostaticly by inserting metal rods (electromagnetic) into the object to be coated.