By Rich Lindgren, Senior Packaging Engineer, Chainalytics
If you’re confounded about the relative merits of edge-crush test (ECT) corrugated board vs. Mullen Burst-grade corrugated board from a compression strength standpoint, you’re not alone.
These two packaging materials often perform similarly with respect to lab compression. But when it comes to drops, in-stack bulging and rough handling environments, it’s a different story.
Corrugated Packaging Success: It’s All in How You Configure Your Product
As in so many instances, the way you transport, stack/store and handle packaged products makes a big difference in the type of corrugated material that works best:
- For many years, the Mullen Burst test served as the industry standard for grading corrugated board for secondary and tertiary packaging (aka shipping cases). But as corrugators started using more and more recycled content in their corrugated board, users discovered that recycled board of the same basis weight did not always perform as well in the Mullen Burst test (although Mullen board product still had some very good vertical compression qualities).
The Mullen Burst test pressures a rubber diaphragm bubble against the corrugated board in a defined area to measure the pounds of pressure per square inch to burst the board. In general, Mullen Burst-grade boards contain more virgin material, with longer, interleaved fibers, and are best suited to help with product containment and puncture resistance.
- The ECT test–subsequently developed as another sample board test–measures only straight vertical compression force on a board. As the shipping world evolved to more truck-load quantities of homogeneous products, more companies chose ECT board. ECT board’s main benefit is it creates the best ratio of cost vs. compression strength for uniformly stacked shipping boxes.
ECT-grade board usually has a higher recycled content, with fibers that are shorter and worked more, making it less expensive. Often the paper mills that manufacture ECT-grade board use special processes to align the paper fibers vertically to help with top to bottom compression strength. But ECT-grade board often lacks the impact and puncture strength of Burst-grade board.Burst-grade board has it’s own unique applications, and is starting to become more common in e-commerce shipments as well as products that are commingled and floor loaded for retail store distribution. In these environments the secondary packaging needs to protect the product contents against all the other packages it may come in contact with in the back of the dry van trailer. So if you’re a shipper or 3PL shipping and handling warehouses full of homogenous product, for example, and all you do is straight column stacks of product, that do not bulge out against your container and are stored in controlled environments–ECT board might provide the best net-cost benefit.
In the end there are no hard and fast rules: Burst-grade board in many cases will cost a little more, but may get you more bang for your buck!
On the other hand, most companies do not have these ideal conditions: They handle and restack their packages many times within their own distribution channels. And we all know the distribution hazards of shipping in a single parcel environment through UPS or FedEx can also wreak havoc on your packaging design and may require different materials or a different protective packaging strategy. If you’re faced with the rigors of single parcel supply chain, this may be a good time to consider Burst-grade board as a solution.
In this case, you should see much better overall box performance from the Burst-grade board because of the configuration and natural strength of their longer fibers. You can also combine Mullen weight papers with traditional ECT papers to help offset costs and still create a better box. This is still relatively uncommon due to the special paper combinations and high volumes needed.
So the short answer to the question “How do you choose between ECT and Mullen burst board?” is the proverbial “it all depends”: Sometimes ECT is the right choice and saves money in many applications, but Mullen burst board may help in certain distribution channels with decreased damage and improved customer satisfaction.
Rich Lindgren holds lifetime Certified Packaging Professional (CPP) accreditation from the Institute of Packaging Professionals (IoPP) and has extensive experience with both packaging optimization and supply chain cost reduction projects.
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