In this section, we will now study some bonding operations which are made in primary and secondary woodworking jobs. Secondary woodworking includes millwork ( I beams, doors and windows ), manufacture of decorative panels and sandwich panels.
This technique allows to heat and dry very quickly the bond line, and it is used for many different applications, in woodworking and furniture and also in other industries.
When a material is subjected to a high frequency alternative electric field, from 3 to 300 megahertz, the atoms and molecules which form dipoles will move alternatively with the electric field at the same frequency, and these fast movements will cause a fast heating of the materials.
If we subject a piece of wood coated with a water based adhesive to such alternative electric field, the molecules of water, highly polar, will be heated very fast, and the wood will be also heated because it contains water.
Microwaves are also used for fast heating and bonding: their frequencies range from 300 to 3000 MHz.