Blown Film

process

A continuous extrusion process where molten polymer is formed into a tubular bubble, inflated with air, and collapsed to create thin plastic film with uniform thickness and properties.

In Simple Terms

Blown film is like blowing up a balloon with molten plastic. The polymer is heated, extruded through a circular die, inflated with air to form a bubble, then flattened and wound into rolls. This creates the thin plastic films used for bags and packaging.

Why It Matters

Blown film is essential for producing flexible packaging materials with excellent barrier properties and uniform thickness. It's cost-effective for high-volume production and allows precise control over film properties through resin selection and processing parameters.

Technical Details

The process involves extruding molten polymer through an annular die, creating a tube that's inflated by internal air pressure. The blow-up ratio (bubble diameter to die diameter) typically ranges 2:1 to 4:1. Film thickness is controlled by line speed, extrusion rate, and air pressure. Cooling is achieved through air rings.

Real-World Examples

LDPE grocery bag production

Low-density polyethylene with 2.0 MFI is processed through blown film extrusion to create thin, flexible grocery bags with good tear resistance and clarity.

LLDPE stretch film manufacturing

Linear low-density polyethylene resins are blown into films with controlled thickness variation and excellent puncture resistance for pallet wrapping applications.

Multi-layer barrier film production

Co-extrusion blown film combines different polymer layers (like EVOH barrier resins with polyethylene) to create high-performance food packaging films.