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Polyethylene Foam Terminology

Monday, August 31, 2020

If you’ve used polyethylene foam for packaging, you have probably heard the terms: master bundle, slits, perforations, and rolls. But what do they all mean? We answer these questions below,  as well as explain the different types of density that are available.

The most common terms used for polyethylene foam are:

  • Master Roll: refers to the starting width size of the foam. Typically master rolls come in 48”, 60” or 72” widths.

  • Slit: refers to the width the master roll is slit or cut to. For example, if you start with a 72” wide master roll and slit it to 18”,  there would be four slit 18” rolls per master roll. The tolerance on slits is +/-⅛”.

  • Perforations: refers to the perforations put along the length of the master roll. Most manufacturers can only supply up to 96” perforations (perforations repeat every 96”) but Murphy Packaging is able to supply up to 196” perforations. Perforations are used to help operators easily tear the roll into sheets. The tolerance on perforations is +/- 1”.

  • Master Bundle: refers to the number of rolls per master roll. For example, if you take a 72” wide master roll and slit it to 18”, the master bundle would consist of four 18” rolls. Typically, pricing is per master bundle.


Regarding density, the typical polyethylene packaging foam comes in 1.2# density but can also be ordered in 1.7# or 2.2# density if needed. Density is measured by finding the weight of a 12 x 12 x 12 piece of foam. A 1.2# density foam will weigh 1.2 pounds. Sometimes companies go to the higher density foam for more cushioning but typically 1.2# suffices in most packaging applications. Another foam option to increase cushioning is laminated foam, where  a sheet of polyethylene is added to the regular foam rolls. 

We hope this article has helped you better understand foam and the different types and options available. If you have any more in-depth questions, please feel free to contact our foam experts at 847-549-1400.