Blow film extrusion (also called tubular blown film extrusion) is a plastic forming process in which a molten polymer tube is extruded through an annular die, inflated into a bubble with air, and cooled to form a continuous sheet or tube of plastic film.
During blow film extrusion:
- Plastic resin is melted in an extruder and pushed through a circular (annular) die to form a continuous tube of molten polymer.
- Compressed air inflates the tube into a bubble, which is stabilized by internal air and external cooling from an air ring.
- The bubble cools to its softening point (often marked at the frost line) and collapses into a flattened web.
- The resulting film is wound onto rolls for converting into bags, liners, flexible packaging, agricultural films, and other products.
Blow film extrusion is widely used because it enables coextrusion of multiple layers for barrier properties, versatile gauge control via air-ring profiling, and consistent film output for high-volume flexible packaging and industrial film applications.
Learn more about the blow film extrusion process, materials, and quality control on the Blow Film Extrusion overview page.