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Stretch Film Types (Cast vs Blown)

Stretch film is made by either the cast or blown process, and it is sold in hand and machine grades. This sheet compares cast and blown film, explains hand versus machine rolls and pre-stretch, and lists what to ask before quoting.

Ref PK-0108ASTM D4649

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

Stretch film is linear low-density polyethylene (LLDPE) film stretched around a load to hold it together on a pallet. It clings to itself and grips the load as it tries to recover. Cast film is extruded through a flat die onto chilled rolls. Blown film is extruded as a bubble and cooled by air. The process changes clarity, noise, cling and toughness. Both are sold as hand film, wrapped by a person, and machine film, run on a stretch wrapper. ASTM D4649 is a guide to selecting and testing stretch films.

How to identify

Cast film is very clear, glossy and quiet as it unwinds. Blown film is hazier and louder, and feels tougher when you try to puncture it. The label gives gauge, width, length, core size and whether the roll is for hand or machine use. Film gauge is in gauge units: 100 gauge is 1 mil, or about 25.4 microns. See the film gauge conversion chart.

Cast vs blown

Property	Cast	Blown
Clarity	High; easy to scan labels	Hazier
Unwind noise	Quiet	Loud
Cling	Usually two-sided cling	Often one-sided cling available
Puncture and tear resistance	Lower	Higher
Load holding	Good for uniform loads	Better for sharp or irregular loads
Cost per pound	Usually lower	Usually higher

Hand vs machine film

Item	Hand film	Machine film
Typical widths	Narrow widths for hand wrapping	Wider widths for stretch wrappers
Roll weight	Light enough to carry	Heavy rolls on the machine
Stretch	Limited by the operator	Set by the machine, often with powered pre-stretch
Handle	Separate dispenser or hand core	Fits the machine carriage

Key points

Ask about the load: weight, shape, sharp corners, cold storage and shipping distance.
Machine film must match the wrapper: width, core size and whether it has a powered pre-stretch carriage.
Higher gauge is not always stronger. Film quality and stretch level matter as much as thickness.
Cold and freezer loads may need film rated for low temperature.
Pre-stretched hand film is a separate product. See pre-stretched and high-performance stretch films.

Common mistakes

Quoting by gauge alone without seeing the load.
Using cast film on sharp-edged loads that puncture it.
Ordering machine film with the wrong core for the wrapper.
Overstretching hand film so the load is wrapped loosely at the top.

Governing standards: ASTM D4649 (guide for selection of stretch, shrink and net wrap films). Film maker data sheets.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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