Thermal laminating films are made by coating a film such as polyester, polypropylene, nylon, etc. with a thermal polymer based plastic adhesive. During the extrusion coating process the adhesive is treated to increase its surface energy to a specific level which enhances the adhesives’ ability to wet-out as it is laminated onto the print which improves the ability to the adhesive to stick to the item being laminated.
The measurement of the surface energy is called dyne level. Our thermal films for traditionally printed output are treated to a range of coated – 42 & uncoated - 38 dynes. Over time the dyne treatment slowly decays and as the dyne level drops the adhesive loses some of its adhesion.
The industry standard recommended shelf life for all types of thermal laminating films is 1 year. This does not mean that film older than 1 year is no good it only means the film’s adhesion level has dropped below its ideal level and therefore the manufacturer no longer stands behind its performance. It really depends on what is being laminated.
Standard laminating film is thermally-activated, it should be stored in a cool, dry place away from direct sunlight. If the film is exposed to high temperatures for an extended period of time, the adhesive can activate and the layers can fuse together.