A very commonly used material in the industry is corrugated cardboard boxes., which have the function of loading the product during its stowage, it is in this way that the ECT (Edge Crush Test) and the BCT (Box Compression Test) have gained importance as relevant data in the technical specifications of these materials, however these values of the material can present great variations due to the humidity contained in the papers that constitute the corrugated cardboard.
As we know ECT is defined as the compressive strength of a small corrugated cardboard test piece, usually 2 × 2 inches, while the BCT is the resistance to the vertical load or the stowage of the entire box already assembled, these resistances are achieved by the cardboard manufacturer based on several elements, among them: the grammage of the papers involved, their structure, if it is a single-wall or double-wall cardboard, the type of fiber, the level of recycling, and very important the level of humidity contained.
The Mexican Institute of Packaging and Packaging Professionals, IMPEE, has a testing laboratory for almost all types of packaging materials, serving a wide variety of companies in Mexico and other parts of the world., and in its beginnings we found it curious the coincidence that in the rainy season the amount of analysis that we carry out on corrugated cardboard boxes increased significantly, over time we were able to observe that precisely the users of these boxes, in the rainy season, had more problems with them, so they needed to know the real resistance of the boxes they acquired, given this we decided to analyze the tests we had carried out in recent years, finding that humidity was a fundamental factor in the behavior of these boxes .
Generally, when preparing a technical specification for a corrugated cardboard box, data such as: dimensions, type of flute, structure, ECT resistance, BCT, in some cases still resistance to explosion or Mullen, and for cases where the Boxes are automatically assembled on the production line. Rigidity data is requested, mainly on the bending lines. However, in one of the 99% cases, nothing is specified on the subject of humidity.
There are two methodologies to evaluate the humidity in a corrugated:
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1. Moisture percentage
This test simply tells us the percentage of moisture contained in the cardboard, and this can be evaluated from a hygrometer, which has two points with which it evaluates the percentage of humidity that exists in that portion of the cardboard measured, this determination is very simple and fast, since it is enough to place the device on the cardboard analyzed and thus obtain the percentage of moisture.
There is another methodology to determine the percentage of humidity, which is done from a thermobalance. The methodology consists of placing a small section of corrugated cardboard in the thermobalance, which will heat the material until the moisture contained in it completely evaporates. This equipment determines the initial and final weight of the material, being able to calculate the percentage of moisture contained in it. material.
This method is slower and more accurate than the hygrometer, however it should also be considered that for some cases the hygrometer is an excellent alternative, especially when it is necessary to analyze boxes that are in a certain warehouse far from our laboratory. In these cases, the hygrometer can be easily carried given its size and used anywhere, but not the thermobalance that requires special conditions for its use. In whatever way this determination is, it specifically tells us the percentage of humidity that the material we are analyzing has, at that precise moment, of course without knowing the antecedent regarding the conditions in which it was stored, the time, etc.
