Welding Plastics by High Frequency

In order to weld two or more sheets of plastic, their joints must be heated up by pressing the sheets together at the same time until the melting temperature is reached. The pressure should be maintained until the weld cools down.

Principles of high-frequency plastic welding

Polar polymers such as PU, PVC, PET and EVA heat up when they are exposed to a high-frequency field. When welded at high frequency, plastics between the electrode (mould) and the table heat up evenly due to dielectric losses caused by the high-frequency current. Bearing in mind that the electrode and the table are usually cold and tend to cool down the external surface of plastics that are in contact with them, the highest temperature is reached at the welding joint, where it is needed the most. Therefore, plastics melt on the inside in order to keep cold on the outside. This makes it possible to apply a high-power density to the weld, which results in very short welding times that range from 1 to 5 seconds. No other method available for welding provides a quality similar to the one offered by high frequency welding.

General uses of high-frequency plastic welding

High-frequency welding machines are essential in the industry of bags where no leaks are allowed: clinical blood and plasma bags, and inflatable items. Other common applications are: reinforcements in carpets, upholstery, sunshades, covers and bags, truck tarpaulins, blister packs, folders, dossiers and rainwear.