Application of a computer model to evaluate the ability of plastics to act as functional barriers

A simulation model computer program, which accounts for not only the diffusion process inside the polymer but also partitioning of the contaminant between the polymer and the contacting phase, was developed based on a numerical treatment, the finite element method, to quantify migration through multilayer structures. The accuracy of the model in predicting migration was demonstrated successfully by comparing simulated results to experimental data. For this study, three-layer co-extruded high density polyethylene (HDPE) film samples, having a symmetrical structure with a contaminated core layer and virgin outer layers as the functional barriers, were fabricated with varying thickness of the outer layers and with a known amount of selected contaminant simulant, 3,5-di-t-butyl-4-hydroxytoluene (BHT), in the core layer. Migration of the contaminant simulant from the core layer to the liquid food simulants was determined experimentally as a function of the thickness of the outer layer at different temperatures. The computer program, developed as a total solution package for migration problems, can be applied not only to multilayer structures made with the same type of plastics but also to structures with different plastics, e.g. PP/PE/PP. This work might provide the potential for wider use of recycled plastic, especially polyolefins, which have lower barrier properties, in food packaging, and simplification of the task of convincing the FDA that adequate safety guarantees have been provided. Copyright © 2003 John Wiley & Sons, Ltd.