Functional Barrier Studies on Multilayer PET-Films

A functional barrier (FB) can be generally defined as a package construction that limits the amount of migration compounds from the package to an acceptable degree. Most commonly the package is a multilayer structure and the migrating compounds originate from the package interior encapsulated by plastics barrier layers. The degree of "acceptability" which is controlled by the toxocological evaluation or the organoleptical impact of the respective compound is either defined by law through individual specific migration limits or a general threshold of regulation or by the quality assurance requirements to a certain product. The FB efficienca - understood as a migration related term - depends on the numerous parameters which are connected with the type of polymer and foodstuff as well as the food packaging application. Since one of the more important parameters is the plastic's diffusivity, materials such as PET have an advantage over low diffusivity plastics such as polyolefines which le ads to the current market developments with respect to PET recycling. In the presented study, the functional barrier behaviour of three-layered coextruded PET films with a contaminated center layer was investigated in dependency of the FB thickness, time and temperature of storage conditions, nature of the PET contact matrix as well as chemical structure and molecular weight of the contaminant. From the result, a number of conclusions can be drawn dealing with minimum requirements to FB thickness and the workability conditions for the FB concept as well as FB efficiency testing.