Polyethylene: Polyethylene comes in low density (LDPE), medium density (MDPE), or high density (HDPE). Shrink Film uses low density (LDPE) or linear low density (LLDPE), a tougher choice which has better heat seal strength, but contains more haze. Polyethylene is more cost effective than other shrink films. It shrinks 50% – 65% machine direction and 0% – 25% transverse direction.
PVC: Polyvinyl Chloride. More expensive than Polyethylene, PVC is a tough, stiff, very clean film. The oriented version is used mainly for shrink film applications. Cleaner than Polyethylene, PVC shrinks at a lower temperature. The shrink is 65% – 75% machine direction and 10% – 30% transverse direction.
Polyolefin: The strength, clarity and high gloss of Polyolefin make it a good film for retail packaging. A very high shrink film in both directions 50% transverse and 80% machine direction. This is the most expensive among shrink film solutions.
Density: Weight per unit volume. Films with a low density offer more coverage per weight of film.
Center Folded Film: Film folded in half in the machine direction and then wound into roll form.
Forming Head (Plow): A mechanical device used to shape flat or center fold film into the desired bag shape needed for a particular package.
Heat Sealing: Joining plastic films by controlled application of heat and pressure to the area being sealed.
Lap Seal: A method of sealing, plastic films where the two pieces to be sealed are over-lapped, then heated to form a seal.
Machine Direction (MD): The direction parallel to that taken by the majority of molecules in plastic film, or the direction of the film web as it moves through the film-making machine. Also called Longitudinal Direction.
Shrinkage / Percent Shrink: The decrease in dimension of a film when it is subjected to heat.
Transverse Direction (TD): The direction at right angles to that taken by the majority of molecules in a plastic film or the direction at right angles taken by the film web as it moves through the film-making machine.