Sorption Model
Water sorption behavior across broad relative humidity ranges is mathematically modeled by extending classical monolayer absorption theory into multilayer polymer systems. Physical chemistry defines the gab sorption isotherm as the three-parameter equation describing equilibrium moisture content in bio-polymer and cellulose matrices up to high water activity levels. This model accounts for distinct binding energies between surface-bound water and bulk water layers.
Equilibrium State
Cellulose matrices interact with ambient moisture through primary sorption sites on accessible hydroxyl groups. The Guggenheim-Anderson-de Boer equation fits experimental sorption data across relative humidity levels from ten percent to ninety percent without the premature divergence seen in traditional models. Parameter values reflect the monolayer moisture capacity, the binding energy of the primary monolayer, and the interaction energy of secondary absorbed layers.
Converting plants use these mathematical curves to predict how paperboard stiffness changes under fluctuating warehouse conditions. Barrier-coated paperboard designs rely on accurate equilibrium data to evaluate shelf-life requirements for moisture-sensitive dry food packaging. High-density coatings reduce overall moisture capacity, while natural unbleached fibers retain higher hygroscopic absorption profiles.
Activity Limit
Laboratory measurements generate sorption curves using gravimetric vapor sorption systems at constant temperature. Deviations from predicted values occur when structural hysteretic effects cause desorption curves to diverge from absorption curves. The gab sorption isotherm provides the mathematical framework for calculating moisture equilibrium in cellulose packaging substrates.
