What are the differences between Blown & Cast films?
Cast Film is typically different from Blown film because of the way the plastic is oriented and cooled. In the Cast process, film is cooled more rapidly than in the blown process, film is cooled more rapidly than in the blown process. The faster the cooling, which is induced by the chill rollers, causes single direction orientation in the film. In other words, the polyethylene molecules are cooled so quickly that the molecular structure is formed longitudinally in long, two direction branches. By contrast, Blown film is cooled slowly by air while the tube of plastic is drawn upward. The slower cooling allows for the polyethylene molecules to become oriented in all direction. This slow cooling causes crystals to form thus causing the haze associated with blown films. The differences in these two manufacturing processes produce the following characteristics in cast and blown films.
