Preserving the strength of corrugated cardboard under high humidity condition using nano-sized mists

The paper evaluates the adsorption of water vapor and compression strength of three types of commercially made corrugated cardboard boxes for packing strawberry, mizuna and broccoli. The experiments were conducted on the specimens and empty cardboard boxes at constant temperature and 95% relative humidity (RH). The samples were stored under the environments of two types of mists, namely nanomist and ultrasonic-mist over a period of 7 days. Nano-sized mist, which are called nanomists and defined as particles of about 60 nm in diameter, easily evaporate and are considered not to damp the corrugated boxes in comparison with the larger size ultrasonic-mists. The change in moisture content of the samples was first measured at intervals of 6, 12 and 24 h and then daily over 7 days. Compressive strength test was measured by the means of using a tensile and compression testing machine. The results revealed that moisture content of both specimen and cardboard box tests exposed to the nanomist and ultrasonic-mist at the end of experiments was 19.9% d.b. and 30.4% d.b., respectively (dry basis: g-water in material/ g-dry weight) although temperature and relative humidity were almost the same for both cases. Furthermore, the strength of cardboard specimens conditioned with nanomist after 7 days at 5.8 °C and 94.2% RH decreased by 44.3–56.9% whilst under ultrasonic-mist condition it reduced by 66.5–70% depending on the types of cardboards. Similarly, maximum compressive load of corrugated cardboard boxes exposed to nanomist and ultrasonic-mist decreased gradually over the time. It was analytically predicted that the boxes exposed to nanomist maintained its maximum compressive load at 28%, whereas those exposed to ultrasonic-mist remained at 14% after 7 days. The maximum compressive load of corrugated cardboards exponentially decreased with an increase in moisture content.