ISO 13821 standard specifies a method for determining the edge crush resistance. This method is particularly relevant as it is designed to avoid "edge effects" that can distort test results. Using this technique, a rectangular piece of the sample is cut and its edges are waxed before undergoing a crushing test. The application of force is done in the direction of the flutes.
This standard is applicable to various types of corrugated board, including single-wall, double-wall, and triple-wall corrugated board. It can also be used to test samples taken from corrugated boxes and other converted products. However, when it comes to waxed corrugated board, it is important to ensure that the heat used during the waxing step does not affect the corrugated structure. This is controlled by observing that failure during the test always occurs far from the waxed edges.
The result of the edge crush resistance is expressed in Newton per unit length (N/m) and must be reported with an accuracy of 1 N/m. Test reports should include a series of specific information, including a reference to ISO 13821 standard, a complete description of the tested sample, the test result, and any unusual observations during the test.
The accuracy of this test method has been confirmed during its validation. It is important to note that the test is considered valid if failure occurs far from the waxed edges, indicating that the edge effect has been effectively controlled.