" " wisno wood furniture finishing: UV Coating for wood finishing

Tuesday, October 27, 2009

UV Coating for wood finishing

Ultra violet cured coating (UV coating) is the other answer for the requirement of paint product which is more environmental friendly. The UV coating is very less in releasing the "expensive and pollutant" solvents. It also require little energy for drying and produce a very strong film layer. The ultra violet cured coating drying very fast, he need only few minute to be dry and produce hard coating. The curing reaction stimulated and catalyzed with ultraviolet radiation. The reaction mechanism is quite complex, but it can be simply described as follow: 
The coating contains a polymerized resin that will do the polymerization reaction with an energy ignition. When the coating is irradiated with the ultraviolet light with certain intensity, then free radicals that will accelerate polymerization reaction are generated. The polymerization is curing the coating to make a hard and strong film layer. 

uv coating equipment
 Roller coater for UV coating application

There are 3 components required for the formation of film layers, polymerized resin, photo initiator and ultraviolet light. The resin is the material that will polymerize to create a layer of film. Photo initiator is a substance that absorbs radiation from the environment into the resin to initiate polymerization reactions, with photo initiator spurred by free radicals is so fast and then formed to begin the drying reaction. The ultra violet light is the energy that a needed to initiate the reaction. 
The resin material that used to make UV coating is usually oil free unsaturated polyester or acrylic. And the initiator is benzoin used for polyester and acetophenones for the acrylic. The UV coating will produce the hard and strong film coating in the finishing.

The advantages of UV coating
  • The resulting film layer is very strong and hard, resistant to scratches and solvent.
The film produced by this coating is very strong, stronger than the the acid curing or polyurethane clear coating. The UV coating is the proper material to be used for the finish that require the strong and high resistant film.  It is most used to finish for he parquet flooring or top tables that need maximum protection and strength.
  • The drying process is very fast, and does not require high temperatures
With the help of UV ray,  the coating will be dry very quickly. The application process is usually  done in a series of equipments; a roller or automatic spray gun to apply the coating and the UV light to cure the coating. Out of the equipment the coating is already totally dry and hard film is already built. The product is ready to be packed; it does not need long drying time. No need the drying room and the finishing process is done very quickly.
  •  End at relatively low cost compare with another coating.
UV coating material is made with a high solid content, up to 98%. This material almost does not use thinner either in the application or in the mixing. All the paint materials that is applied  will coat and form a film layer on the surface finishing. This material is more efficient in application; although the price of coating is relatively more expensive compared with others, but it need less amount materials to make the same thickness of film layer. 
With less solvent releasing, this coating is also very friendly to the environment.

While disadvantage of this coating are:
  • This coating requires a series of machines an automatic spray and ultra-violet lamp that is expensive.
This paint will dry only if there is an ultraviolet light with sufficient intensity, so the application requires a series of equipment with an expensive ultra-violet lamp as oven. This paint is usually applied in a set of equipment the first is a roller coater or automatic spray equipment, then followed by UV lamps for drying. The UV applicator equipment is considered as big machine which is expensive.
  •  Its uses is limited to a flat product.
This coating needs UV lamps for drying, whereas the UV ray is harmful to health. The UV ray can cause cancer if expose to human skin. Since that, the UV lamp circuit should be in a closed circuit. This condition limit the uses of the UV coating. Until now the coating is only workable to be applied to the flat panel. It may still can be applied on the uneven surface, but still on the flat form. Althugh theologically it can applied in complex form by spray and dried in special room with UV lamp, but it will create difficulty in the sanding and it does not economical. 


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