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IN DETAIL MATERIAL
level in the bottles at every given moment, however in the interval of time studied the loss of CO 2 can be considered to be approximately linear with time. Therefore it is possible to calculate the CO 2 loss rate in units of g/(L·24 h), which allows for a relative comparison between the different variants. From Figure 3, it is evident that the use of PEF as a barrier layer in multilayer PET bottles can also be an effective measure to extend the shelf life of carbonated drinks aswell as oxygen- sensitive beverages. Furthermore, when compared to the monolayer PET bottle of the same mass and design, a multilayer bottle with 10 % PEF achieved a barrier improvement factor above 2. This translates to a doubling of the shelf life, which is in line with or even outperforms market incumbent multilayer bottles containing up to 7% polyamide. Sustainability value of multilayer PET-PEF bottles
multilayer bottles containing polyamide is absolutely necessary to remove as much of the incompatible barrier material. A well-producedpolyamidebasedmultilayer barrier bottle is therefore optimized for delamination to occur during flaking and washing. Recycling of such multilayer bottles relies heavily on the capability of bottle preform and bottle production as well as on the efficiency of the elutriation step to avoid the devaluation of the quality of the PET recyclate. The separated polyamide flakes cannot be further recycled independently, and are commonly incinerated which leads to the release of N2O into the atmosphere. N2O is a greenhouse gas which has an effect 298 times more severe than CO 2 . Therefore, even if multilayer bottles containing polyamide can be considered as being recyclable, this unavoidable release of powerful greenhouse gases will significantly worsen the carbon footprint of such a bottle. PEF’s chemical composition contains no nitrogen, and it is far more compatible with PET so therefore does not necessarily need to
undergo such extensive removal during recycling. An increased yield as well as reduced carbon footprint can therefore likely be achieved in industrial recycling of PEF based multilayer PET bottles. Avantium is currently performing an extensive LCA study of PEF in multilayer bottle applications which will be published in the course of 2021. Conclusions – and a call to action! The current barrier materials utilized in multilayer bottles, suchas polyamide, offer sufficient performance at a reasonable cost, but pose significant doubts in terms of their fit with recycling infrastructures and the circular economy. The recyclability of PET multilayer bottles with polyamide is conditional, with such limitations as only being used in colored bottles and/ or at a maximum layer percentage at a limited market penetration. Furthermore, the recycling of multilayer polyamide bottles also heavily relies on the efficiency of the decontamination step, where the vast majority of the polyamide must be removed by the recycler to avoid severely affecting the quality of the recycled PET. Recyclers are therefore left with the problem of finding the delicate balance between quality (removing polyamide as much as possible) and quantity (not sacrificing the yield of rPET). When it comes to performance PEF is a very valid alternative to polyamide barrier layers, matching shelf life extension at a similar or slightly higher dosing level. However, PEF comes with significant added value: it is made from renewable sources, and its compatibility with PET is a definite advantage during recycling. PEF truly represents an innovative solution to be added to the toolbox of designing for recycling and circular products. It is good news for recyclers and converters, but is especially valuable for those brand owners who are loudly and proudly announcing their commitment towards building a more sustainable world.
During recycling, the decontamination via air elutriation of flakes from PET
6,3
PET monolayer 5% PEF layer 10% PEF layer 7% Nylon layer
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5,9
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Time [days]
Fig 2: Carbonation level with time for 500 mL 19,7 g bottles, courtesy of Logoplaste Innovation Lab. The bottles were filled with carbonated water, stored at room temperature (20-23 °C) and the CO 2 level measured by FTIR method.
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