Chemical Acceleration
A mathematical framework relates the rate of chemical reactions or molecular diffusion to temperature changes. In paperboard packaging, arrhenius kinetics governs the accelerated migration of volatile compounds and the degradation of barrier coatings during thermal processing. The equation assumes that molecules must overcome a specific energy barrier to react or move through a polymer matrix.
It establishes the limit of safe usage for coated papers exposed to baking temperatures or hot filling.
Thermal Sensitivity
Food contact laboratories utilise elevated temperatures to execute migration tests in shorter timeframes than actual shelf life requires. This acceleration relies on the exponential increase of diffusion coefficients with temperature. When temperatures rise, the molecular motion of polymer chains within a synthetic barrier layer increases, which accelerates the passage of potential migrants.
Chemical reaction rates double or triple with every ten-degree rise, depending on the activation energy of the specific compound.
Activation Energy
Packaging developers calculate the barrier lifetime by measuring diffusion rates at several high temperatures and extrapolating the results back to ambient storage conditions. These calculations require precise determination of the activation energy for each migrant in a specific barrier material. Standard tests on polyolefin-coated paperboards use these values to ensure that protective barriers remain effective over the intended shelf life.
The model ceases to be accurate when the polymer undergoes a phase transition, such as melting or glass transition, because the transport mechanism changes abruptly, making linear extrapolation invalid and leading to incorrect safety margins.
