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What's the difference and why is cast film (in our opinion) better?
The numbers don’t lie. Increasingly, business owners are shifting away from traditional blown film packaging and choosing cast film instead. With improved efficiency and sustainability standards, cast film is used by around 70-80% of the industry globally.
Yes, the popularity of cast film may be enough to convince you to make the switch. However it’s worth understanding how these films are made too. In this way you can make an informed decision on which way to go…
Blown Film. This is the traditional way of producing film and takes its name from the process used to create it. Heated resin is blown through a circular die, and a thick layer of extruded film emerges as a large bubble. The bubble can be many feet tall – and it is this height that allows the film to gradually cool before rollers collapse the bubble and flatten the material for shaping onto rolls.
The very nature of blown film makes it a pre-stretched product, and the thickness of blown film is adjustable dependent on the diameter of the tube from which it comes.
Cast Film. Cast film is created by feeding a sheet of heated resin through a flat die. The molten material emerges from the die and out onto larger chilling rollers which cool and solidify the material. It is then ready for trimming and rolling.
Cast film is minimally pre-stretched compared with blown film giving it improved depth of drawing for thermoforming operations. The cooling process can be used to produce different characteristics in the final product. Cast film can be thinned by winding the film out of the roller faster than it is extruded.
There are likely to be many factors to consider when choosing which film to use. These may include the environmental conditions (is it cold or frozen?) storage and transportation processes, and what level of pre-stretch is needed. Here is a quick breakdown of the pros and cons of each type of film.
Has a higher resistance to puncture; preferred for wrapping sharp-edged products and heavy loads such as masonry and construction materials
Film offers less clarity due to crystallisation which occurs during manufacture
Has a high level of cling