Archive: Nov 2020

Mullen Burst Test vs. Edge Crush Test (ECT)

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Optimizing your corrugated boxes to find the perfect balance between protecting your product and minimizing excess packaging (i.e., excess costs and environmental impact) is a science. The science involves using empirical data from testing the corrugated board that makes up the box. Two standard tests are the Mullen Test and ECT or edge crush test.

Mullen Test

The Mullen test is named for the instrument used to conduct the test, which was engineered by John W. Mullen in 1887 and sold to the Parsen Paper company. Although using corrugated for boxes didn’t become mainstream until the early 20th century, the Mullen burst test would become the method for testing corrugated strength for a while.

Why is it used?

  • The Mullen test is indirectly related to a carton’s ability to withstand internal or external pressure. For example, an item might puncture the box, or a sharp edge of the product might protrude from the box during handling.
  • The Mullen burst test is used if boxes will experience rough handling, are manually taken off and put on trucks, or may move around during shipping. Most importantly, the Mullen test is used when burst is the primary concern for performance in the supply chain.

How is corrugated tested?

The testing instrument has two platens with circular openings in their centers. A sample of the corrugated board is clamped between them.  A diaphragm is hydraulically expanded, distending through the lower platen and pressing on the sample until it bursts. The maximum hydraulic pressure reached when the sample ruptures is recorded as its bursting strength and is measured in pounds.

Edge Crush Test (ECT)

In the 1990s, corrugators started using a higher percentage of recycled material. The fibers of virgin paper are long and bind together, giving it more strength than the shorter fibers of recycled material. It was noticed that although the burst test results were lower, boxes were still being stacked with no noticeable issues. The edge crush test became an industry standard for strength when stack is the primary concern for performance in the supply chain.

Minimum basis weight is required for the burst test, but ECT does not have this requirement, so lighter weight materials can be used while still providing a higher crush resistance. When comparing two cartons – one burst test rated and one ECT rated, the ECT box will weigh less.

Why is it used?

  • ECT is directly related to stacking strength and how much weight can be applied to the corrugated per square inch.
  • This test helps determine if a box can withstand other loaded boxes’ weight when shipped on a pallet.

How is corrugated tested?  

A sample of corrugated board is placed on edge (flutes perpendicular) between to platens, and force is applied until the sample buckles. The results are recorded in pounds per lineal inch of load-bearing edge but represented as ECT. For example, you may see a box rated as 40 ECT.

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