The sealing must ensure airtightness and tightness in the presence of contaminants. The design of the film must take into account the sealing temperature and hot tack properties which measures the heat-sealing strength between the films. However, they are designed considering the product to be packaged, the packaging machine, the transport and handling phases of the packaging. The sealing layers are available as follow: low density polyethylene, metallocene hexene polyethylene (C6), obtainic polyethylene (C8), C8 plastomers, EVA copolymer.
The peelability function is achieved in two different ways: (1) peelability of the layers due to incompatibility (easy peel) where the added additive creates a hermetic seal but easy to open with different forces according to the customer's requests (generally from 3 -6 N / 15mm); (2) peelability due to breaking of the layers (burst peel) where the opening force is unique and characterized by a high value at the beginning which then decreases after opening. All peelables are designed based on the welding surface. They are available for: polypropylene (PP), polystyrene (PS), expanded polystyrene, polyethylene terephthalate (PET).