Technical guide with sources · ROLL Lab

Paper cores for stretch film and flexible films

ROLL Lab · updated 24 October 2026 · sources at the end of the page

The problem: the film’s grip

An elastic wound film squeezes the core from every side, with pressures that in practice range from about 5 to over 100 bar. Failure can come later: within 72 hours with cast film, within 7 to 14 days with blown film. The symptom is an inside diameter that closes up and a roll that will not come off the shaft.

What to specify

• Minimum radial crush in bar with the method (CCTI T-158 or T-159), with a margin over the pressure measured on the line.
• Flat crush to ISO 11093-9 as a production check.
• Delivery moisture up to 8%, measured in an oven.
• Inside diameter with ISO 13542 tolerance, measured at three points.

Hand rolls and jumbos

Hand stretch film rolls use light cores (Ø 38–76 mm, thin walls). Jumbos and machine rolls need a 3" core with verified radial strength, because bigger rolls and thinner films (down-gauging) raise the pressure.

Core weight in hand rolls

Stretch film is bought by weight, and the core is part of that weight. On a hand roll of a few kilos, a heavy core takes metres of film away at the same price. That is why lightweight cores of around 140 g exist: always ask for the net film weight separately from the core weight.

How to spot a core at its limit

The first sign is an inside diameter that closes by a few tenths of a millimetre in the days after winding. Measure it with a three-point bore gauge straight away, at 72 hours and at 14 days. A reduction beyond 0.8–1 mm points to insufficient radial strength or a damp core. Dr. Core helps you tell the two causes apart.

All applications

Frequently asked questions

Sources

1. ISO 11093 (parts 6, 7, 8, 9)
2. ISO 13542
3. CCTI T-158, T-159
4. ROLL Lab calculation