Determination and Prediction of the Lag Times of Hydrocarbons through a Polyethylene Terephthalate Film

Polymeric materials can be used as functional barriers to prevent contamination of food from the environment or from other packaging components, e.g. mineral oil hydrocarbons from printing inks. Polyethylene terephthalate (PET) is such a promising barrier material. From permeation studies found in the scientific literature lag times, diffusion coefficients or permeation rates towards organic chemicals could not derived because of the slow diffusion process of the permeants in PET. Knowledge about lag times or diffusion coefficients for different permeants, however, is essential for the evaluation of the barrier properties of PET films towards organic contaminants, e.g. mineral oil hydrocarbons. The aim of the study was to develop automated permeation testing method in order to determine the lag times of high-barrier films. From the lag times, the diffusion coefficients as well as the partition coefficients of the alkanes were calculated. In addition, the permeated amounts were simulated by use of diffusion models. Therefore, the lag times can be predicted under different experimental conditions as used in the current study. The results of this study show that the investigated 12 mu m PET film is an effective barrier towards mineral oil hydrocarbons. For example, the predicted lag time for n-octane or n-dodecane at 40 degrees C is 8.8 and 210years respectively. Copyright (c) 2014 John Wiley & Sons, Ltd.