GAB Isotherm Calculations for Microfibril Barrier Sorption Qualification
GAB isotherm parameters determine microfibril moisture sorption capacity and establish precise water activity thresholds for barrier packaging compliance.
Gas Permeability
Mass Transport
Mass transport through a solid barrier under a pressure gradient identifies the specific resistance of a material to the passage of air or other fluids. Calculations of gas permeability determine the shelf life of food products by measuring how much oxygen or CO2 enters or leaves the package.
Diffusion Rate
Molecules move through the polymer or coating layer in a multi-step process involving adsorption at the surface and migration through the bulk material. The temperature of the environment affects the kinetic energy of the gas and the free volume within the barrier layer. Higher temperatures lead to faster transmission rates and can compromise the integrity of sensitive goods.
Different gases permeate at different speeds depending on their molecular size and solubility in the barrier. Modern testing equipment uses sensitive sensors to detect parts per million of the target gas as it emerges from the dry side of the film.
Material Selection
Synthetic coatings or metallic foils are often applied to paperboard to reach the low transmission rates required for long-term storage. The barrier effectiveness drops if the layer is folded or creased during the converting process. Small pinholes or cracks can create a path for gas that bypasses the diffusion mechanism entirely.