Basics PEF and PET
Basics PEF and PET bottle recycling Last year Synvina, the joint venture of Avantium and BASF, received interim approval from the European PET bottle platform (EPBP) for the market introduction of PEF up to 2 % of the total European PET consumption. The actual recyclability of a PEF end-product, as any product, will however depend on how it is designed and where it is launched, influencing what type of collection and sorting infrastructure is present and if this can divert the products components to recycled material streams. Why then, did the EPBP already grant an interim approval? One of the reasons was that Synvina already at an early stage gathered and shared a significant amount of data that demonstrated that PEF is not only sortable, but that low levels of PEF are compatible with PET. Although not unique, this is a rare feature for plastics while the more common incompatibility has caused issues for some bioplastics in the past. In this article we take a deeper look into the nature of this compatibility and how it can put PEF in a unique position for a circular bottle economy. Why introduce a new bottle material? PET bottles are amongst the most successful examples of plastics recycling. However, in smaller size bottles, PET by itself is not always able to reach a logistically relevant shelf life. For example the mechanical criteria of a 8 oz (237ml) bottle can be met with 9-13 grams of PET while yielding a CO 2 shelf life of only 4-6 weeks (4.2→3.5 Vol). To increase this, a bottle is often complemented by a coating or barrier layer. Coating equipment is not always economically attractive, for example if (seasonal) demand changes require flexible output. Using multilayer preforms for bottle production on the other hand may impose recyclability limitations for the bottles; infrared sorting equipment may still recognize them as PET while the barrier layer, if not removed, may disrupt rPET quality. PEF has been previously shown to enable logistically attractive shelf lives in small bottles and this is continuously being improved, as exemplified by the recent achievement of 16 and 20 weeks shelf life in 10g and 14g PEF bottles respectively. Simultaneously PEF more and more exceeds mechanical performance over PET, while PET remains economically unattractive to produce from 100 % renewable sources. As such, PEF is becoming increasingly attractive as a bioplastic that brings material reductions beyond any other solution for small size plastic bottles. And because PEF is chemically different than any other plastic, near-infrared sorting equipment can automatically sort them from the PET stream. Controlling after-use material streams As most new (non-drop-in) bioplastics, PEF is chemically different from known materials and therefore has a unique infrared spectrum. This allows PEF bottles to be sorted out using automated near-infrared (NIR) sorting technology. Recent ambitions for higher recycling targets drive increased use of such technology to create separate streams beyond the most common streams of PET and HDPE, for example PP, PS and opaque PET. These infrastructure changes may also accommodate the creation of streams for bioplastics with interesting end-of-life options such as composting or recycling into new high value products. In the case of PEF, the similar chemistry to PET may even allow the use of existing PET Vol. CO2 Vol. CO2 4,30 4,20 4,10 4,00 3,90 3,80 3,70 3,60 3,50 3,40 3,30 0 5 10 15 20 25 4,30 4,20 4,10 4,00 3,90 3,80 3,70 3,60 3,50 3,40 Weeks 3,30 0 5 10 15 20 25 Weeks 237 mL Bole -17.5% CO 2 237 mL Bole -17.5% CO 2 recycling technology and assets. Nevertheless, automated sorting is not fail-safe and many recovery systems rely to a large extent on human sorting, either by the consumer or by professional sorters, for whom a PEF bottle is not always easy to distinguish from PET. PEF and PET compatibility Synvina has done multiple recycling tests using PEF and PET resins and bottle flakes, and consistently found that low levels of PEF did not affect the thermal profile of PET in a DSC experiment, while increasing levels started to induce melt point depression particularly at longer extrusion times. Furthermore, extrudates remained transparent. Further analysis by 13C NMR showed increased splitting of the furan ring ipso carbon with increased residence time, which an earlier study on PET copolyesters attributed to a transition from a blocky long-segment to a random co-polyester [1]. These observations confirm that PEF and PET undergo trans-esterification during processing, yielding a random co-polyester as the end-product. Extruded pellets remained transparent and had a lower tendency to form crystalline haze than neat reprocessed PET. 50 bioplastics MAGAZINE [04/18] Vol. 13
Basics By: Jesper van Berkel, Technical Application Manager, Synvina Amsterdam, The Netherland The 2 % and 5 % concentrations were selected for testing following the EPBP protocol at PTI Europe, which comprises the typical steps of a recycling process at 5kg-scale. These steps are outlined below with some of the critical control points. • Bottle grinding g Dust formation • Flake washing & Drying g Flake and/or water discoloration, sticking PEF in PET T g, mid T m, peak 0 % 79 °C 249 °C 2 % 79 °C 248 °C 5 % 78 °C 247 °C 10 % 78 °C 245-247 °C 25 % 76 °C, 86 °C 207 °C, 240-246 °C • Re-extrusion into pellets g IV loss, side products or fumes • Solid State Polymerization g IV build, sticking of pellets • Injection into plaques/bottles with 50 % vPET g Transparency, color, bottle properties PEF in RPET (plaques following EPBP route with 50 % vPET) 2x g PEF Molecule PET Molecules { None of the steps in the recycling process were found to display surprising phenomena in the presence of PEF, and all intermediate and final intrinsic viscosity measurements yielded comparable values. The only notable difference was that for the 5% loading the coloration of final plaques, as expressed by Δb* = 2.1 compared to the PET reference, was higher than the acceptable range of Δb* = 1.5. This is an aspect which we expect to improve with further improvements in PEF resin color. 1.5 L Bottles could be blown of the final resin, yielding properties as per the table below. Conclusion PEF can serve as a high value bioplastic material for applications where PET alone is not sufficient, and opposed to other barrier technologies this value can be retained when the bottles are recycled. Although yet to be demonstrated at scale, this can offer many opportunities; PET bales with nonrecyclable barrier bottles can be avoided, while PET bales with PEF may be used to reduce haze formation or as a source of separately accumulated PEF for individual rPEF campaigns with high value output. Ultimately, a separate stream of PEF bales can be created for an effective after-use economy. [1] H. Ma, M. Hibbs, D.M. Collard, S. Kumar, D.A. Shiraldi, Macromolecules 2002 (35), 5123-5130 www.synvina.com Property (1.5L 43g bottle) Final composition Burst Pressure Vol incr. at burst Thermal stability Drop test vertical 4°C Drop test vertical 22°C Top Load @1.0 mm deflection Method Mass balance Linear increase Linear increase 4.25 vol CO 2 , 24h 38°C, Base pushup 1.8 m, vertical bottom down, 72h 1.8 m, vertical bottom down, 72h Typical Result PET 2% Route 2 5% Route 2 PET+ 1% PEF PET+2.5% PEF 11.0 bar 11.8 bar 11.5 bar 565 mL 594 mL 565 mL -4.0 mm -4.2 mm -4.1 mm 8/8 OK 8/8 OK 8/8 OK 8/8 OK 8/8 OK 8/8 OK Empty 225 N 240 N 225 N bioplastics MAGAZINE [04/18] Vol. 13 51
