Quantification of the Sorption Behavior of Polyethylene Terephthalate Polymer versus PET/PA Polymer Blends towards Organic Compounds

Polyethylene terephthalate (PET) bottles are widely used for beverages. Oxygen-sensitive beverages, however, often require the use of barrier materials or oxygen-scavenging additives incorporated into the PET material, which is in most cases polyamide (PA). As a consequence, small amounts of polyamide are entering the PET bottle-to-bottle recycling feedstream. Aim of the study was therefore the determination of the sorption behavior of bottles made of different PET/PA blends in comparison with a PET reference. As a result, PET test bottles containing blended PA amounts of up to 1000ppm do not show a sorption behavior for the investigated model compounds, which is different from pure PET material. Therefore, polyamide impurities in the recycling streams coming from polyamide barrier bottles will not lead to a different sorption/remigration behavior as pure PET bottles. Consequently, evaluations of PET recycling processes will still be valid for feedstream materials conta ining such small amounts of polyamide from barrier bottles. On the other hand, the introduction of 8% of polyamide decreases significantly the sorption of organic compounds into the bottle wall.