Meaning
Algebraic or differential requirements applied at the edges of a physical domain to solve migration problems. Designers apply mass transfer boundary conditions when modeling how a migrant leaves a plastic surface and enters a liquid food simulant. These rules determine whether the surface concentration remains constant or changes based on the surrounding environment.
Interface Partition
Equilibrium at the contact surface is governed by a partition coefficient that relates the concentration in the polymer to the concentration in the solvent. Mass transfer boundary conditions account for this discontinuity to ensure that the chemical potential is balanced across the interface. This step prevents the calculation of unrealistic flux values at the start of the simulation.
If the solvent is a poor absorber, the boundary condition limits the total migration.
Surface Resistance
External resistance to the movement of molecules can occur when the surrounding fluid is not well stirred. Mass transfer boundary conditions incorporate a mass transfer coefficient to describe this convective barrier.
Flux Continuity
Proper application of these constraints ensures that the amount of material leaving the polymer equals the amount entering the food. Mass transfer boundary conditions are the primary tool for defining the interaction between a container and its contents. This definition is required for any regulatory compliance simulation.
