Today we will study bonds and products which require resistance to humidity and water, such as doors, windows, sandwich panels, exterior panels for wood houses, and also some products which are made in primary woodworking plants such as laminated parquets.
In most cases UF glues are used and the doors are pressed at 80 to 90°C for a few minutes.
The glues should display high viscosities and high solids in order to fill the gaps between the facings the frames and the cores if these parts are not perfectly flat.
Glue add-on is usually from 200 to 300 g / m2.
The setting speed may be increased by applying first the acidic hardener on both facings, and then the glue onto the hardener.
In some countries, the doors are cold pressed and PVAc adhesives are used. A large number of doors are stacked and then pressed in one single operation.
Reactive PU hot melts are also used and they provide very fast setting resulting from the cooling of the hot melt and this leaves some time for the reactive PU to crosslink or cure afterwards.