MATERIALS | THIN WALL PACKAGING
PCR material. The material is transparent, uses more than 80% recycled content and can be made on existing PET sheet co-extrusion equipment. The specific heat resistance can be ‘tuned’ depending on the level of recyclate. For instance, a structure using 90% recyclate (and two outer layers of Akestra) can
perform at 75°C, while a grade with 70% recyclate and 30% Akestra operates at 95°C.
Above: Perstorp’s Akestra
copolyester can be
combined with PET to create hotfill applica- tions
This gives it a wider operating range than HIPS or PS, he said. Regulatory benefits include increased food
safety, while it also offers rigidity, clarity and heat resistance, he said. There is also a reduced carbon footprint: he claimed that 100,000 tonnes of PS would generate around 365,000 tonnes of CO2. Akestra and 30% rPET would reduce this by 24%, while Akestra and 80% rPET would cut it by 56%, he said. (This excludes processing into sheet.) “This hotfill thin wall circular packaging solution goes way beyond the long-term PPWR target for transparent PET trays,” he said.
PP benefits Andreas Goeldel, commercial technology director at Grupa Azoty, said that polypropylene offers an innovative approach to sustainable packaging. A key advantage of PP for thin wall packaging is the ability to design single-material products: for instance, takeaway coffee packaging can be made from PP rather than from cardboard, polyethylene and polystyrene. Similarly, in a food container, it could replace a coated cardboard – making it easier to recycle.
Some other advantages include low – or competitive – global warming potential compared with other polymers; low density – especially
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compared to metal and glass (allowing significant reductions during transport); and the ability to use it in a high-speed process such as rapid thermo- forming.
PP is also easy to separate and sort – thanks for IR detection – and relatively easy to clean, he said. “It also has FDA approval for food usage,” he
said.
Its linear olefinic structure and lack of aromatic content or halogens also makes it an ideal feed- stock for chemical recycling processes, he added. Goeldel said that the company is developing a number of high-end thermoforming grades.
PP expansion Synthomer also talked about replacing materials such as PS and PET with PP – augmented by additives. The company’s Luan Gaviao and Synco de Vogel told delegates that – despite its advantages – PP is difficult to thermoform due to problems such as sagging, a narrow processing window and slower production cycles. However, the company has carried out trials on its Plastvance T additive – which it says proves that the material can “modify PP so that it behaves like PS” buy raising the stiffness and widening the processing window of PP. In the trial, the company used a Battenfeld-Cin-
cinnati sheet extrusion line to make 0.5mm thick PP sheet. The material used a PP grade from Sabic, plus 16% Plastvance T. This was compared with 0.6mm HIPS sheet. The presenters said that the thermoformed PP cups showed “no compromise on performance” – and several advantages. For instance, they had a 44% higher top load, better haze and gloss, higher oxygen and water vapour barrier and more uniform wall thickness. In addition, it was around 38% lighter. There were also potential cost reductions,
through both material usage and packaging licence fees (in Germany).
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