Relative Humidity and Absolute Moisture Content Effects on the Compression Strength of Corrugated Boxes

ABSTRACT Corrugated boxes are relatively inexpensive and used extensively to contain and protect consumer products as they move through the distribution system, providing a much-needed function in today’s economy. These boxes are constructed from paper, and therefore the mechanical properties of the boxes vary significantly with moisture content in the paper and available in the atmosphere. Relative humidity regularly varies between 30 to 90 % depending on location and time of year. Above a relative humidity of 30 %, paper fibers are affected, resulting in a decrease in the top-to-bottom compression strength of corrugated boxes. Therefore, understanding the moisture effect on box compression strength is essential for the containment, protection, and safe shipment of products. The goal of this study is to characterize the effect of relative humidity and, subsequently, the effects of moisture content on the compressive resistance of corrugated boxes. A total of 3,000 industry supplied boxes are used to evaluate moisture content and compressive strength at seven relative humidity conditions from 30 to 90 %. Three sets of conditions are repeated to test repeatability for a total of ten batches tested. The moisture content for 3 out of every 10 specimens is recorded using a loss-upon-drying moisture balance. Results indicate a second-order polynomial increase in moisture content as a function of relative humidity. The compression strength of corrugated boxes is found to vary linearly with moisture content for the range tested and follows a second-order polynomial decrease with increasing relative humidity. The data from this study are compiled into a table of corrugated box strength reduction factors for comparison with the results from previous studies.