Spraying process of UV powder coating
The powders can be sprayed on most MDF types using conventional corona or tribo charging guns. In the latter case, the addition of a tribo additive to the formulation is recommended. Applied layer thickness is between 35 and 100 um, depending on the type of application. Pre-heating of the board can aid powder application in some cases.
To melt the applied powder efficiently, medium wave infrared radiation (IRM) is used. Further flow out is achieved by using a combination of IRM and convection heat. When coating shaped MDF substrates, the use of convection is specifically recommended to achieve uniform warming-up of the entire panel surface. A typical heating cycle used to melt/flow out formulations .
The above formulations, both clear and pigmented, can be cured with normal mercury vapor lamps. For our tests, two electrodeless lamps of 160 W/cm each irradiate the molten film, passing under the lamps at a line speed of 4-9 m/min. For clear formulations, complete cure can be achieved with a UV dose of 800-1,000 mJ/cm2 (UVA); for pigmented systems, a dose of 2,000 mJ/cm2 (UVA) is recommended.