Blown vs. Cast Film
March 25, 2020
When shopping for stretch wrap, you may run across the terms "blown" vs. "cast." These descriptors refer to the way the film is made—and yes, they matter. Blown and cast stretch films have different properties, strengths and weaknesses.
Cast stretch film is created by extruding a polymer resin through rollers. This is a newer manufacturing method that is highly controllable and economical, resulting in a film that is higher performance and more cost effective for many applications. They are also generally clearer and shinier when applied to the load, unwind quietly and resist tear propagation. Cast films make up roughly 75% of the stretch wrap market.
Blown films are made by blowing a large bubble of air into the hot resin as it emerges from the extruder. The film is pulled off the bubble and into rollers as it cools. Blown films are more expensive, but they have advantages for applications requiring extra load stabilization or durability. Compared to cast stretch film of the same gauge, blown films are more puncture and tear resistant, have higher levels of cling and are extremely stretchy. That extra clinginess has a downside—blown stretch film is very noisy to unroll! When properly applied, the extra stretchiness of blown films can deliver superior load securing power, though it also makes it challenging to maintain the proper tension on the film. Blown films are the best choice for low-temperature environments like refrigerated or freezer storage rooms and packing areas.
