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 Plastics and rubber  

Preheating and welding

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High-frequency (HF)

Applications and potential benefits

  • +Welding plastics
  • +Preheating plastics before molding
  • +Preheating rubber before vulcanization
  • +Product dries quickly and evenly
  • +High energy efficiency
  • +Less wear and tear on molds
  • +Better quality molded parts
  • +Fast temperature rise

Find out more

HF welding techniques are based on dielectric heating of the materials to be welded. Dielectric heating occurs when a conductor containing polar molecules is placed in an alternating current field. The electrical charges in the material then try to follow the changes in direction of the field. In the process, friction occurs between the molecules, creating internal heat.

When HF welding is done, the plastic materials to be welded are inserted between two metal plates (electrodes) that are powered up at high frequency (generally at 27.2 MHz). The molecules in the materials to be welded start to vibrate and heat up, causing the materials to soften. The technique of placing two layers of plastic in a high-frequency field like this and squeezing them together produces a very strong weld.

Some plastic materials heat up better than others in a high-frequency field. The following thermoplastics lend themselves particularly well to this type of welding:

  • PVC (polyvinyl chloride)
  • TPUR (thermoplastic polyurethane)
  • PUR (polyurethane)
  • PET (polyethylene terephthalate)

See also