TWI Frequently asked questions
by Felicity Chipperfield
Thin thermoplastic films, of less than 0.5mm can be hot bar or impulse welded. The necessity for the heat to conduct through the film to the joint imposes a restriction on the thickness of material that may be welded. A practical limit of approximately 1mm exists.
The most widely used materials for joining by hot bar or impulse welding are polyethylene, polypropylene, polyester, polyvinyl chloride and polystyrene. Often, multi-layer films are used with each layer providing a different functional role e.g. strength, oxygen barrier, seal. Applications include food packaging (sachet, trays, pots) and medical uses (tablet packs, medical devices).
