Blown Film vs. Casting Film: Exploring the Differences

Blown Film vs. Casting Film: Exploring the Differences

Oct 01, 2023

In today's packaging and plastics industry, we often come across the terms "blown film" and "casting film." Both these processes play essential roles in the production of plastic films and products, but what sets them apart? This article delves into the distinctions between blown film and casting film to help you better understand their characteristics and respective applications.

Blown Film Technology

Blown film is a common plastic film manufacturing technique, where the fundamental principle involves melting plastic pellets and then blowing the molten plastic into a bubble-like film through a circular die (or blow head). This bubble is subsequently cooled and shaped to form the desired film. The blown film process typically includes the following steps:

  1. Plastic Melting: Plastic pellets are melted through a heating process, transforming them into a pliable liquid.

  2. Blowing the Film: The molten plastic is blown into a bubble shape through a blow head and then stretched and cooled.

  3. Shaping and Cooling: The bubble is stretched and cooled to form the required film.

Casting Film Technology

In contrast to blown film, casting film technology involves uniformly distributing liquid plastic on a horizontal plane, followed by cooling and solidification to create the film. This process includes the following steps:

  1. Plastic Melting: Plastic pellets are melted through heating into a liquid state.

  2. Casting the Film: The molten plastic is uniformly spread on a surface, often through extrusion or pouring.

  3. Cooling and Solidifying: The plastic cools on the surface, forming the film.

Key Differences

  1. Process Principle: The most significant distinction lies in the process principle. Blown film is created by blowing plastic into a bubble and then cooling it into a film, while casting film is manufactured by uniformly distributing molten plastic on a plane and cooling it.

  2. Film Characteristics: Blown film typically has higher tensile strength and tear resistance because of its more ordered molecular structure. Casting film is usually flatter and suitable for specific applications like printing.

  3. Production Speed: Blown film production is generally faster than casting film production, as it can be continuous.

  4. Applications: Blown film finds wide application in food packaging, agricultural films, trash bags, and more. Casting film is commonly used in special packaging, labels, optical applications, and the like.

In summary, blown film and casting film are two distinct plastic film manufacturing technologies, each with unique characteristics and applications. Understanding the differences between them can aid manufacturers and consumers in choosing the most suitable type of film for their needs. Whether you're shopping for packaging film or using them in production, being aware of these technological disparities will help make informed decisions.