Atmospheric Condition
Gaseous water content within the sealed environment of a shipping unit influences the structural integrity of corrugated packaging. The container microclimate vapor represents the airborne moisture that migrates between the cargo and the internal air during transit across different temperature zones. Environmental variables determine the risk of condensation or hygroscopic absorption by the liners.
Condensation Risk
Temperature fluctuations during sea transport force the air to reach its dew point on the inner walls or ceiling of the steel box. As the container microclimate vapor cools, the water molecules lose kinetic energy and transition to a liquid state known as container rain. This moisture drips onto the top layers of pallets and softens the paperboard fibres.
Damaged boxes lose their ability to support the weight of the layers above. Desiccants and thermal liners are used to capture the water before it reaches the packaging.
Moisture Equilibrium
Paper is a hygroscopic material that naturally seeks to balance its own water content with the surrounding air. The container microclimate vapor fluctuates as the sun heats the metal exterior and the interior cools at night. This cycle draws moisture out of the timber pallets or the paper products themselves.
When the air warms again, it holds more moisture and pulls more from the cargo. Continuous cycling leads to warping or delamination of the adhesive bonds in corrugated board. Monitoring these levels provides data for adjusting the board grade or the type of sizing used in the manufacturing process to resist humidity.
Proper ventilation or the use of specific barrier materials can mitigate the impact of the vapor on sensitive print finishes.
