heatsealable

Heatsealable is an adjective used to describe materials, surfaces, or coatings that can form a sealed joint when exposed to heat under pressure. In packaging, heat-sealable films, laminates, or foils contain a heat-sealable layer that fuses to another compatible surface to create a bond.

Most heat-sealable layers are thermoplastic polymers such as polyethylene-based sealant layers (LDPE, LLDPE, EVA), polypropylene, or ionomer. These layers are often co-extruded or laminated onto a substrate to provide both sealing capability and barrier properties. The seal is generated by applying heat and pressure with a sealing tool, followed by cooling to set the bond.

Common sealing equipment includes impulse sealers, continuous- and intermittent-band sealers, and seal bars with temperature control. Sealing parameters—temperature, time (dwell), and pressure—must be matched to the materials and film thickness; some processes also use a cooling interval to improve seal strength.

Applications include food packaging, medical devices, pharmaceuticals, and consumer goods. The advantages of heat sealing include speed, simplicity, and the potential for strong, hermetic seals without solvents. Limitations include sensitivity to surface contamination or moisture, material incompatibilities, and the possibility of seal failure if the seal layer is damaged or the process parameters are misadjusted. Recycling and disposal considerations also depend on material construction.

Quality is assessed through seal strength and integrity tests, such as peel strength or burst tests, following standardized methods (for example, seal strength tests on flexible barrier materials). For reliable performance, manufacturers specify seal temperature ranges and process windows for each material system.