Chemical Mobility
Movement of low molecular weight additives from a polymer film into the adjacent paperboard or packaged product alters the physical properties of the materials. When plasticizer migration occurs, it causes the protective barrier coating to become brittle while potentially contaminating the packaged goods. This phenomenon is driven by concentration gradients and high temperatures during storage.
Substrate Interaction
The rate of this movement is determined by the molecular weight of the plasticizer and the chemical structure of the host polymer. In many cases, the migration of these additives is accelerated when the packaging is exposed to fatty foods or organic solvents that act as extraction agents. This extraction leaves the polymer coating prone to cracking during subsequent handling.
Performance Loss
As the coating loses its plasticizer, the protective layer becomes stiff and starts to peel away from the paperboard substrate. This loss of flexibility leads to a dramatic decrease in the folding and creasing performance of the carton, causing cracks at the score lines. To prevent this, packaging formulators use polymeric or high molecular weight plasticizers that are less mobile and remain locked within the polymer matrix.
This design ensures that the packaging remains flexible and retains its barrier performance throughout the intended shelf life.
