Transport Rate
Mass transfer analysis of water vapor moving through a solid packaging material requires a parameter to measure how fast molecules migrate under a concentration gradient. This property is the moisture diffusion coefficient, which determines the rate at which humidity penetrates the fiber matrix of the board. This value depends heavily on the temperature and density of the paperboard.
Material Barrier
High-density papers and those treated with polymer coatings or wax barriers have a much lower coefficient, which prevents water from entering the sheet. The coefficient of the bare board is highly variable because the porous structure of cellulose allows both gas-phase and surface diffusion to occur simultaneously. Controlling this transport rate is necessary when designing cartons for dry or moisture-sensitive products.
Storage Stability
Corrugated containers stacked in humid warehouses slowly absorb water from the surrounding air, with the rate of absorption governed by this parameter. As the fiber network reaches a higher moisture content, the stacking strength of the box decreases, which can lead to pallet collapse during long-term storage. Measuring the moisture diffusion coefficient allows packaging engineers to calculate the safe storage life of a packed product before the structural integrity of the carton is compromised.
This calculation is a central part of risk management in distribution logistics.
