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Poly(ethylene terephthalate) (PET) is used in several packaging applications, especially for beverages. Due to the low concentration of potential chemical compounds like polymer additives or monomers leached out of the polymers and found in food or beverages, the compliance of a PET packaging material is shown often by use of migration modeling. Diffusion coefficients for migrants, however, are rare in the scientific literature. The aim of the study was to develop an equation for the prediction of diffusion coefficients in PET on the basis of activation energies of diffusion for possible migrants in PET. As a result, a correlation between experimentally determined activation energies of diffusion EA and the volume of the migrant V was established for PET. In addition, a correlation of the pre-exponential factor D0 with the activation energy EA was found. Combining both correlations lead to an equation where the diffusion coefficients DP are predictable from the molecular volume V of the migrant. The equation might be useful for migration prediction and consumer exposure estimations

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Mineral oil migration from cardboard packaging into foodstuffs is recognized as a serious problem for the consumers. Within this study, a fast automated method for the determination of mineral oil permeation through barrier films was developed. The method is using 15 defined standard substances representing mineral oil chemistry instead of complex mineral oil mixtures. The developed method can be used for the evaluation of the barrier properties for polymer films regarding mineral oil components from paper and cardboard packaging materials. For all investigated permeants and polymer films, the logarithm of the permeation rates and the logarithm of the vapour pressure result in a linear correlation. The correlation can be used to compare the permeation properties of different barrier films. From the results of this study, it can be concluded that 12 mm oriented polyethylene terephthalate or 15 mm oriented polyamide are effective barriers towards mineral oil components. The barrier effect of pure polyolefin films is negligibly poor because the permeation is too fast and the lag time is in the range of a few hours at 40 C. As a consequence, the migration of mineral oil components from cardboard can be significantly reduced if inner layers of good barrier materials such as polyethylene terephthalate or polyamide are used.

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Poly(ethylene terephthalate) (PET) bottles are widely used for beverages. Knowledge about the migration of organic compounds from the PET bottle wall into contact media is of interest especially when post-consumer recyclates are introduced into new PET bottles. Using migration theory, the migration of a compound can be calculated if the concentration in the bottle wall is known. On the other hand, for any given specific migration limit or maximum target concentration for organic chemical compounds in the bottled foodstuffs, the maximum allowable concentrations in the polymer CP,0 can be calculated. Since a food simulant cannot exactly simulate the real migration into the foodstuff or beverages, a worse-case simulation behaviour is the intention. However, if the migration calculation should not be too overestimative, the polymer-specific kinetic parameter for migration modelling, the so-called AP value, should be established appropriately. One objective of the study was the kinetic determination of the specific migration behaviour of low molecular weight compounds such as solvents with relatively high diffusion rates and, therefore, with high migration potential from the PET bottle wall into food simulants in comparison with real beverages. For this purpose, model contaminants were introduced into the bottle wall during pre-form production. The volatile compounds toluene and chlorobenzene were established at concentrations from about 20-30 mg kg(-1) to 300-350 mg kg(-1). Phenyl cyclohexane was present at concentrations of 35, 262 and 782 mg kg(-1), respectively. The low volatile compounds benzophenone and methyl stearate have bottle wall concentrations of about 100 mg kg(-1) in the low spiking level up to about 1000 mg kg(-1) in the highly spiked test bottle. From these experimental data, the polymer specific parameters (AP values) from mathematical migration modelling were derived. The experimental determined diffusing coefficients were determined, calculated and compared with literature data and an AP' value of 1.0 was derived thereof for non-swelling food simulants like 3% acetic acid, 10% ethanol or iso-octane. For more swelling condition, e.g. 95% ethanol as food simulant, an AP' value of 3.1 seems to be suitable for migration calculation. In relation to PET recycling safety aspects, maximum concentrations in the bottle wall were established for migrants/contaminants with different molecular weights, which correspond with a migration limit of 10 microg kg(-1). From the experimental data obtained using food simulants and in comparison with beverages, the most appropriate food simulant for PET packed foods with a sufficient but not too overestimative worse-case character was found to be 50% ethanol. In addition, it can be shown that mass transport from PET is generally controlled by the very low diffusion in the polymer and, as a consequence, partitioning coefficients (KP/F values) of migrants between the polymer material and the foodstuff do not influence the migration levels significantly. An important conseq...

Typical contamination and the frequency of misuse of poly(ethylene terephthalate) (PET) bottles are crucial parameters in the risk assessment of post-consumer recycled (PCR) PET intended for bottle-to-bottle recycling for direct food contact applications. Owing to the fact that misuse of PET bottles is a rare event, sustainable knowledge about the average concentration of hazardous compounds in PCR PET is accessible only by the screening of large numbers of samples. In order to establish average levels of contaminants in PET source materials for recycling, PET flakes from commercial washing plants (689 samples), reprocessed pellets (38) and super-clean pellets (217) were collected from 12 European countries between 1997 and 2001. Analysis of these materials by headspace gas chromatography revealed average and maximum levels in PCR PET of 18.6 and 86.0 mg kg-1 for acetaldehyde and 2.9 and 20 mg kg-1 for limonene, respectively. Acetaldehyde and limonene are typical compounds derived from PET itself and from prior PET bottle contents (flavouring components), respectively. Maximum levels in PCR PET of real contaminants such as misuse chemicals like solvents ranged from 1.4 to 2.7 mg kg-1, and statistically were shown to result from 0.03 to 0.04% of recollected PET bottles that had been misused. Based on a principal component analysis of the experimental data, the impact of the recollecting system and the European Union Member State where the post-consumer PET bottles had been collected on the nature and extent of adventitious contaminants was not significant. Under consideration of the cleaning efficiency of super-clean processes as well as migration from the bottle wall into food, it can be concluded that the consumer will be exposed at maximum to levels < 50 ng total misuse chemicals day-1. Therefore, PCR PET materials and articles produced by modern superclean technologies can be considered to be safe in direct food applications in the same way as virgin food-grade PET.