When it comes to making a decision on which film to use for industrial films, bags, and sheeting the best starting point is to determine whether or not the application would be best served with blown film or cast film. There are major differences in the manufacturing process for each, as well as the benefits and drawbacks to each type of film. Additionally, most manufacturers specialize in either blown film or cast film.
Blown Film Process Illustration
Blown Film is manufactured through a process in which plastic resin is heated and stretched to the desired thickness by an air inflation system, resulting in a very large bubble of film that is allowed more time to cool by the surrounding air.
Cast Film Process Illustration
Cast Film is manufactured through a process where plastic resin is heated and stretched to the desired gauge and then as soon as it completes the heating process, the film is rolled over chilled rollers to cool the film.
There are advantages and disadvantages to blown film and cast film that will determine which type is preferred for each application. These characteristics and properties are a result of the manufacturing process of each.
Blown Film Properties
|Maximum Toughness||Noisy Unwind|
|Puncture Resistance||Less Control over Thickness|
|Less Scrap when Manufactured||Longer Cooling Times|
|Short Production Runs Available|
Cast Film Properties
|High Transparency, Haze, Gloss||Double-Sided Cling (Naturally)|
|Uniform Thickness/Gauge||High Gloss = Glares, Reflections|
|No Limits on Thickness||Longer Production Runs|
|High Barrier for Gases, Moisture, Aromas||More Scrap|
Blown film is most commonly used in tube form (bags and sacks) or sheets, shrink film, stretch film, bags, liners, laminated film, barrier film, medical grade film, and agricultural film. Thickness typically ranges from 0.5 mil to 10 mil. Mostly in applications where clarity is not critical, but strength is. Blown film can be used in simple processes: mono-layer (bags), and complex processes: multi-layer structures (food and medical packaging).
Cast film is commonly used in thermoforming applications. Additionally, you will use cast film in most retail applications where clarity and uniform thickness are important (bakery items, flower wrapping, photo album covers, etc.).
The applications for blown film and cast film are diverse and unique. There may be a better solution for your current application.
Contact one of R.V. Evans’ sales professionals to discuss the material, machines, and processes you’re currently using and the potential in your industrial packaging processes at 1-800-252-5894 or visit our website at www.rvevans.com
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