FlexPAC provides packaging solutions in a wide variety of materials, one of which is corrugated fiberboard (a.k.a. cardboard). Corrugated fiberboard boxes provide great protection while your goods travel to their destination, is renewable, recyclable, sustainable and cost-efficient which is why it is STILL the most popular choice for packaging. If you’ve ever delved into the world of corrugated boxes, you may have wondered why sometimes the strength of corrugated board is described as Mullen grade (Burst Strength Test) and other times it’s described as ECT grade (Edge Crush Test). These two rating systems were developed at different times by the boxing industry for different reasons. Let me explain… The goal is to choose the right board grade for the right application. The production of paper liners at paper mills is guided by whether the combined corrugated fiberboard will be an ECT or Mullen grade and then the Mullen, or ECT, testing is performed in labs, often by the corrugated manufacturers themselves. The Mullen Burst Test, developed in 1887, is the longest running industry standard and is measured in pounds. Often “Mullen grade” is described as 200# or 275# as examples. When a Mullen test is performed, a swatch of corrugated board is clamped into a Mullen tester and, then using hydraulics, force is applied to the flat side of the board via rubber diaphragm. The pressure is slowly cranked up until the diaphragm bursts through the corrugated fiberboard sample. In the case of a 200# material, the sample should not fail (burst) for anything less than 200 lbs per square inch. To see what the Burst Test looks like, check out this short video by Pack Test:
Essentially, a Mullen grade corrugated board is formulated to hold up against rough handling and punctures from internal and external forces. Mullen grade boxes are ideal for shipping product via common carriers because there are a lot of opportunities for damage as the box travels through their systems. Packages are often tossed around, and they ride on conveyor systems where they can crash into other packages. Over the last century, the production of goods has increased exponentially. Millions upon millions of boxes are unitized (stacked) on pallets in warehouses, in tractor-trailers for travel by land, or in shipping containers for travel by sea. In these scenarios, the primary forces applied to a box are coming from gravity and the weight of the boxes stacked above it. The bottom box in a stack must be able to support the weight from above which is why ECT board grades were developed. The Edge Crush Test was developed in the 1990s and is performed by taking a small rectangular sample of corrugated fiberboard and applying force to the fluted edge to measure the board’s resistance to crushing. ECT board grades do not need to have much puncture resistance so the paper liner weight can be less than the paper liner weight of a Mullen grade, which often results in cost savings due to using less material in the composition of the board. ECT board grades are described with a number designator (32 ECT, 44 ECT, etc.), which is defined by an Edge Crush Tester that measures the compression rate on the linear edge of the board. You can see how the crush test is performed:
Using the appropriate grade of corrugated can reduce cost, not only in the material itself but also in reduced damage and returns while using the wrong board grade could be costing you dearly due to over-packaging your goods. Wondering if you’re using the right board grade? Contact FlexPAC for a free needs analysis today. Our Solutions Providers’ expertise in corrugated packaging will ensure that you’re using the right box for the right application, every time.