Bursting Test vs. ECT

Over recent years many of our customers have asked us the difference between the bursting test and edge crush test (ECT), and how it relates to their boxes.  Both tests are different and measure separate properties of the material; however they both deal with measures of durability and strength.  Within each test there are many grades.
When one of these tests is performed on a random sample,  the results allow the sheet manufacturer to assign a certain grade.  Usually the manufacturer will plan to run a certain grade and knows what combinations of liner and medium will meet the test requirement. It is important to point out that even if a run is designated to be a certain test grade – for example  ECT,  it could also be burst graded and vice-versa  This is proven in day to day operations because it is not typically possible to tell the difference between similar grades of ECT and burst test sheets with the naked eye because they look and feel similar.  The only way to verify they meet a certain grade would be to perform the test on a sample, and in many cases the results may show that the particular sample meets a burst grade as well an ECT grade, thus proving that all corrugated sheets can fit into both testing methods, and overlapping of grades is common.

The bursting test sometimes refered to as the “mullen test” sets requirements as to the weight per unit area of material.  A given burst test corrugated sheet must weigh a certain amount per 1000 sq. ft.  When the weight of the material is met a  grade is given with units of pounds per square inch (psi).   This pressure is directly related to a boxes ability to withstand external or internal forces and thus to contain and protect a product during shipment.  Burst grades are usually used to withstand rough handling where puncture and tear resistance is needed.

ECT is a measure of the edgewise compressive strength of corrugated board.   ECT is directly related to the stacking strength of a box . It is measured by compressing a small segment of board on edge between two rigid plates perpendicular to the direction of the flutes until a peak load is established. This is measured in units of pounds per lineal inch of load bearing edge (lb/in), and reported as an ECT value.  ECT grades are primarily used when boxes will be stacked over a period of time, and the product weights are known.  A calculation can be performed using these variables to choose an adequate grade.

When designing a packaging solution, the best designers begin with the end in mind. Every packaged product has its own unique set of problems to solve. These include physical characteristics of the product, the mode in which the package will be shipped or stored, and the functions the package will be asked to perform. Your corrugated salesman should be the first point of contact to assist you in choosing the correct grade of corrugated you should be using for your boxes.

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