Today, boxes are one of the most widely used boxes for shipping and storage. Recently, e-commerce has increased the demand for affordable packaging and shipping solutions and corrugated boards have quickly filled up the void. They are low cost, durable, eco-friendly and can also be reused. However, having the right type of corrugated box matters. Corrugated boards vary a lot in strength, thickness, chemical resistance and more. Multiple standard testing procedures are used to determine how well a corrugated box will hold up to external influences. Here are some of the common corrugated box testing methods that manufacturers use to check the corrugated boxes.
Bursting Strength Test
Bursting strength test simply checks the strengths of the walls of the corrugated board. In the Bursting strength test, a pressure is applied to the walls of the corrugated box until it bursts. The testing procedure applies pressure using a rubber diaphragm. The diaphragm is expanded using hydraulics and as the diaphragm expands, the corrugated board bursts under pressure.
We measure bursting strength in Kilograms per square centimeter. The Bursting factor is given as a thousand times the bursting strength, divided by the grammage of the board.
Edge Crush Test
The corrugated sheet has three or more layers. Generally, a thin sheet with grooves and ridges is sandwiched between two flat sheets. These grooves and ridges, also known as flutes provide anisotropic strength to the box. This means that the boxes can bear more forces from one direction. Edge crush test or ECT simply tests that. Tests that are similar to ECT includes ring crush test and flat crush test. In all these tests, the pressure is applied to a sample until it is crushed.
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Water Resistance of the Gluing
Even though the fiberboard itself can absorb and retain water, the testing the water resistance of the gluing or the sealing is also important. For certain applications, the FEFCO 9 standard is used to test the water resistance of the gluing of the corrugated cardboard boxes.
Cobb Sizing Tester
The raw material that is used in the manufacture of corrugated fiberboards has a tendency to absorb water and retain it. The Cobb Sizing tester is used to test it. First, the corrugated fiberboard is allowed to absorb water. Then, the water is squeezed out of the sample using pressure. All of the water is not removed, some of it is retained by the sample even after it has been pressed using a heavy steel roller.
The difference in weight because of the retained water is known as the Cobb value.
Paper Grammage and Thickness
Grammage and thickness are the two most fundamental properties of the corrugated fiberboards that determine the quality of the box. There is no “best” grammage or thickness mentioned in corrugated boxes specifications and it is completely based on the requirements. When more padding is required, a box with a higher thickness is used. The flutes of the corrugated board are larger and pack more air in them. Thin boards with dense flutes have a high grammage. Such boxes are needed when the packaging should be more compact and rigid.
Puncture resistance tests how well the box can handle the impact made with a pyramid or triangularly shaped weight. The corrugated box testing standards for puncture resistance include FEFCO 5 or ISO 3036.
On corrugated boxes that are printed, scuff proofness tests check how the printed content can handle abrasion. There is the Sutherland Rub Test, with is an industry standard testing procedure. Coated surfaces such as paper, films, paperboards and all other printed materials are tested using this procedure.
Alternative corrugated box testing methods are also available to test resistance to abrasion. These include rotary abrasion testers and even manual wiping.
Box Compression Test
Box compression test, also known as container compression test, is a way to test how much load the box can take on top of it before it gets deformed and how much it gets deformed. It gives a good idea of how many boxes can be stacked together without damaging the contents of the lowermost box. The boxes are tested in different orientations. If the box design makes use of inner supports, such as wood support or corrugated board cushioning, then those are also taken into account.
In fact, most of the rigid packaging testing methods are applicable to corrugated boxes as well.
Chemical Analysis in Corrugated Box Testing
Chemical analysis is required for certain applications where the nature of the fiberboard as well as it’s resistance to certain chemicals are checked. The analysis of the fiberboard involves microscopic examination of the board to see what types of paper are used to make the fiberboard. Moreover, the moisture content, as well as the pH of the board, is also determined.2