Meaning
Mathematical model applied to predict the non-linear migration of additives from a polymer matrix into a food simulant. Biexponential integration accounts for the two distinct stages of diffusion where an initial rapid release is followed by a slower and more stable transfer. The calculation stops being applicable if the polymer structure undergoes a phase change or significant swelling.
Decay Rate
Curve fitting for the migration data relies on two separate exponents to describe the movement of molecules through the plastic. Biexponential integration captures how small molecules like antioxidants or slip agents leave the surface layers before the bulk concentration begins to move. This approach provides a more accurate estimate of consumer exposure than a simple linear model.
Migration Prediction
Software tools used for regulatory compliance frequently employ this method to simulate long-term storage effects. Because biexponential integration tracks the depletion of the additive near the interface, it prevents the overestimation of total migration into the packaged goods. Moulders use these results to select the correct additive loading for a specific shelf life.
Modeling Precision
Validation of the model occurs by comparing the theoretical curve against experimental data points from laboratory extraction tests. Biexponential integration reduces the margin of error when dealing with multilayer films where different resins have varying diffusion coefficients. A successful fit requires high-quality initial data and consistent environmental conditions.
The model remains the primary tool for calculating the diffusion of low molecular weight substances in rigid polyolefins.
