Heat-sealing adhesives are thermoplastic materials that can be coated onto substrate surfaces and later reactivated by heat and pressure. They differ from conventional hot melt adhesives that are applied in the molten state and cooled between substrates in a single step. Typically both hot melt and heat-sealing adhesives are thermoplastic because they do not change chemically when heated and because their bonds can always be reversed by heat.
Heat-sealing adhesives are generally solvent or water-based systems that can be applied as liquid coatings. Some heat-sealing adhesives can also be applied as a hot melt coating via gravure, slotted die, or extrusion processes. These types of heat-seal adhesives are the main focus of this article. Solid, free thermoplastic films (thermosensitive films) can also be used as heat-sealing adhesives. In certain cases an adhesive may not be necessary, as a thermoplastic film substrate itself can be heat-sealed.The heat-seal process can be run at high line speeds, and it has relatively low materials and energy costs.