When silicone oxygen-scavenging films based on singlet oxygen reactions were being developed in the author’s laboratory, exudation of an insoluble oxidation product was observed within a few hours when an otherwise soluble substrate was oxidized.
Such an occurrence is particularly noticeable in silicones that are often poor solvents for organic compounds.
In some forms of active packaging, sustained migration of substances in or out of a packaging plastic is necessary to achieve the desired effect.
Such systems include, for instance, the release of antimicrobials.
Flavors or antioxidants, and uptake of water vapor, oxygen, ethylene or taints.
The polymer required to support these effects may therefore differ from that used in a plastic with an otherwise similar passive role.
The latter roles include that of a heat-seal or barrier layer in a pouch, or a closure liner in bottles.
Restrictions imposed by the diffusion of selected species in polymers normally result in the active layer being as close as practicable to the food.