plastic bags seen on automated blow film extrusion molding line

application insights

Blow Film Extrusion

WHAT IS BLOW FILM EXTRUSION

Did You Know?

Blown film extrusion makes plastic film by extruding a molten tube through an annular die, inflating it into a bubble with air, cooling it (externally with an air ring and often internally via IBC), then collapsing and winding it as a layflat web or tubing. The tube solidifies at the frost line, the location where the melt first drops below its softening point.

At-A-Glance Facts:

  • Also called: tubular blown film; film blowing
  • Typical where: flexible packaging (liners, bags, pouches), barrier films, agricultural film, hygiene, stretch‑hoods
  • Layers: from mono‑layer to 7/9/11‑layer coextrusions for barrier structures (e.g., PE/Tie/EVOH/Tie/PE)
  • Film gauges: commonly ~6–250 µm (application‑dependent)
  • Key geometry terms: BUR (Blow‑Up Ratio) = bubble diameter ÷ die diameter; FLH (Frost‑Line Height) = die‑to‑solidification distance; DDR (Draw‑Down Ratio) relates output, speed, gap, and gauge