Expert knowledge from A-Z
L
A process in which two films are bonded together to combine the properties of these films together.
In a lap seal, the films are stacked at the edges before sealing with the interior side on the exterior side. The films are welded at the overlap; the film seals flush and cannot be peeled open. The package is closed on the bottom and on top with subsequent cross sealing. The seal seam strength is not particularly high, which is why this process is primarily used for providing packaging that simply protects against contact. Lap seals generally use orientated polypropylene, including as a composite. For more refined packaging, triple bonds are often used. It is important that the film is sealable on both sides.
Film QA testing for offset layers; ideally, all of the layers should lie precisely one on top of the other on a film roll. To test this, place a ruler or a similar straight edge on the side of the roll – the height difference is to be no more than 2 mm.
See also "Additive"; used to improve the gliding behaviour of thermoplastics, especially films. Adding to much may adversely affect the properties of the film for printing or welding. The potency of the active ingredient is restricted by food-related specifications.
The luminance (light density) is a photometric value; a measure of brightness with the unit cd/m².
