Study of functional barrier properties of multilayer recycled poly(ethylene terephthalate) bottles for soft drinks

Poly(ethylene terephthalate) (PET) flakes were ground, contaminated, washed, manufactured into multilayer preforms and bottles, and then tested for migration. The model contaminants were toluene, trichloroethane, chlorobenzene, phenyldecane, benzophenone, phenylcyclohexane, and copper(II) acetylacetonate. No migration was detected through a barrier of virgin PET (186 ± 39 μm) into 3% acetic acid food simulant using general methods of testing with a detection limit of 1 μg kg^-1. Migration was <1 μg kg^-1 even for 6-month-old bottles placed in contact with the simulant for a further 6 months; that is, a test period considerably in excess of the shelf life of soft drinks. Neither was migration detectable in the more severe simulating solvents (e.g., 50% aqueous ethanol and 100% ethanol). Targeted analysis by gas chromatography-mass spectroscopy was then used to achieve a sub microgram per kilogram limit of detection and establish the performance of the barrier. Three-layer bottles with the contaminated PET buried were compared with 1-layer bottles in which contaminated PET contacted the food simulant directly. Migration into 3% acetic acid from 1-layer bottles was from <0.2 to 57 μg kg^-1, and the worst-case substance was chlorobenzene. Migration from 3-layer bottles was from <0.2 up to 0.4 μg kg^-1, and the worst-case substance was toluene. Therefore, the virgin PET layer reduced migration from an already low level, by more than 2 orders of magnitude.