The parts that must be bonded are placed in a varying radio frequency
electromagnetic field. Heat results from electrical losses that occur in the
material located between two metal plates or bars, called electrodes. These
electrodes also act as pressure applicators during heating and cooling. The
dynamic electrical field causes the molecules in some thermoplastics to
oscillate, due to their dipole moment. The oscillating movement of the
molecules melts the polymer. When the electromagnetic field is switched off,
the weld cools down and solidifies.
Materials
Only certain materials, which contain molecules with a dipole moment (polar
polymers), can be RF welded. The most widely used material is Polyvinyl
Chloride (PVC).
Nylon sheeting can be RF welded if preheated electrodes are used. Other
plastics can only be welded with the use of polar additives.
