Paperboard Moisture Sorption Dynamics and Water Vapor Permeability Fundamentals
Paperboard moisture sorption and vapor permeability govern pack structural integrity and shelf life through fiber swelling, stiffness loss, and mass flux.
GAB Equation
Sorption Model
Moisture sorption isotherm analysis describes how food and packaging materials absorb water vapor over a wide range of relative humidity. Utilizing the gab equation allows engineers to fit sorption data across a broader range of water activity than simpler mathematical models can handle. This formulation is used for determining the moisture sensitivity of paper and board products.
Mathematical Parameters
Thermodynamic behavior of bound water is captured by three distinct parameters that represent the monolayer capacity, the energy of adsorption in the monolayer, and the behavior of the multilayer water molecules. The gab equation extends the classic bet model by introducing a correction factor for the multilayer water, which accounts for the fact that these outer layers do not behave like pure liquid water. This model provides an accurate fit for water activity levels up to ninety-five percent.
This wide range makes the model highly useful for modeling real-world storage conditions.
Packaging Calculation
Food shelf life predictions rely on this accurate sorption data to design barrier packaging that prevents moisture transfer. Understanding the moisture uptake of the paperboard itself helps converters prevent softening and structural failure in humid warehouses. This mathematical modeling reduces the need for expensive and lengthy physical storage trials.