Heat sealing is the joining of two plastic structures, most often film, sheet, or thermoformed containers, through an adsorption-interdiffusion process.
To form a heat seal, two plastic structures are heated while being held together under slight pressure. Heat is conducted through the structures to the common interface. Generally, one or both of the structures being sealed are coated with a heat-seal coating which flows at temperatures well below the melt or distortion temperatures of the plastic structures being sealed.
The advantages of the hot bar sealing methods are the speed at which seals can be made and the relatively low cost of machinery.