Heat sealing is used for joining thermoplastic films, typically less than 0.5 mm thick.
There are two main types of heat sealing:
Hot-bar welding and impulse welding have found applications in a number of industrial sectors,
but are most widely used in the packaging industry for sealing bags, films, and containers made from thermoplastics. This includes plastic pot and tray sealing for food packaging applications. Many medical devices are also heat-sealed in packages of thermoplastic and plastic coated paper.
The heated region is textured to reduce and control the joint strength. This offers the opportunity to supply a sterile component in an easy-to-open package.
Outer packets for intravenous bags, laminated packs for powders, colostomy bags, and some tablet blister packs are also heat-sealed. In addition to medical and packaging applications, some electronic devices are also joined together by heat sealing, including printed circuit boards, electronic packages, and liquid crystal displays. Unlike some welding and sealing techniques, such as radio frequency welding, heat sealing is not material dependent, and is used for joining many different types of thermoplastic materials.