The main difference between blown stretch wrap and cast stretch is the process by which they are made. These differences also have a significant impact on the availability and price of the films.
The casting process is the same as the blow molding process, where resin beads are fed into a heated barrel and extruded through a narrow slit mold.
The mould then produces a blown stretch wrap which is conveyed along an already cooled rolling path, thereby curing the film.
It then goes through a final production blown stretch stage to be made into large rolls. Extrusion is produced much faster and at a much lower cost per hour of production than extrusion. Machine stretch wrapping is the most common type of film produced by this method.
Resin beads are conveyed through a blown stretch heated machine with a circular mold. The heated resin is forced through the mold and then blown out vertically to form a bubble.
When this formed bubble finishes the process of transforming into a roll of stretch film, it is cooled by the surrounding air. This type of film is blown stretch usually more expensive to produce because the output per hour is less than that of an actor’s film.
Our hand blown stretch wrap is a common example of this type of film. In terms of grip and puncture resistance, it is rated well above our cast films.