Psychrometric Boundary Layer Analysis in Wrapped Paperboard Pallets during Transit
Polyethylene film wraps trap moisture desorbed by paperboard during thermal swings, elevating internal relative humidity and triggering mechanosorptive failure.
Intermodal Transit Microclimate
Environmental Exposure
Fluctuations in temperature and relative humidity inside closed shipping containers during transport determine the moisture risk for packaged paper goods. The intermodal transit microclimate is the localized atmosphere that develops around cargo as it moves through different climatic zones. This atmosphere is highly dynamic, often reaching high humidity levels and causing condensation on container walls, a phenomenon known as container sweat.
The boundary of this environment is defined by the container’s steel structure, which behaves as a sealed thermodynamic system.
Condensation Cycle
During transit, the container is heated by solar radiation during the day and cooled rapidly by ambient air at night. In the intermodal transit microclimate, this temperature cycle causes moisture to migrate from the paperboard packaging and wooden pallets into the air, and then condense on the cold steel ceiling. This condensed water drips onto the cargo, weakening the corrugated boxes and causing mold growth.
Moisture-resistant barriers, desiccant bags, and ventilation holes help mitigate this condensation cycle inside the container.
Performance Risk
Packages that are subjected to high humidity in this microclimate lose up to half of their compression strength. This loss of structural integrity can lead to stack collapse and product damage, even if the boxes were designed to withstand standard warehouse conditions. Ensuring that the packaging material is treated with moisture-resistant sizing or coatings helps prevent this moisture absorption during transit.