MATERIALS | STRETCH & SHRINK FILM
many applications – and has also been used to improve the physical properties of plastic films. Ivan Ramires, product and sales manager at
Gerdau Graphene, said that a 1% loading of its Poly-G graphene additive has helped to reduce the thickness of shrink films by 25%. A conventional 21 micron stretch film will stretch
by around 250% – but one that contains Poly-G stretches by about 350% for a 17-micron film. It means that 10 turns on a pallet will consume 76g of material, rather than 110g – a saving of 30%.
Above: A 1% loading of Gerdau’s Poly-G graphene can cut the thickness of shrink films by 25%
“Choosing alternatives to single-use plastic
stretch films and evaluating environmental trade- offs is challenging,” she said. “They can come at a higher price, make compromises to quality and performance, or even be more damaging to the environment than plastic counterparts.” The company has investigated a number of
alternative materials to secure pallet loads, includ- ing paper, films containing 30% recyclate, and virgin film. These were assessed – using a test devised in-house – against criteria such as damage, cost and environmental impact. The test showed the virgin films were the top performer for carbon footprint, weight and cost. “Virgin films are consistent, high-efficiency performers,” she said. “PCR stretch films fluctuate and introduce implementation risks and significant source reduction is still possible.” A key factor is that stretch film accounts for less than 1% of the total plastic on a pallet loads of bottles, for instance – yet plays a critical role in ensuring that there is no failure. Source reduction can be handled by aiming to use the least amount of material per pallet – at the highest performance and lowest cost. Despite this, few brand owners monitor the amount of stretch used on each pallet. “Stretch wrap is the only material on the pallet
where the amount used is not predefined,” said Lancaster. Tracking how much stretch wrap is used can be achieved automatically – such as with a plant line monitoring system – or with periodic ‘cut and weigh’ operations. One way to reduce usage is to invest in more modern wrapping machinery – which will wrap to the required containment force using less film. Another is to use higher quality film.
Graphene benefits Graphene has been touted as a wonder material in
14 FILM & SHEET EXTRUSION | June 2024
PET improvement Emile Homsi, global leader for R&D at Cargill Bioindustrial, explained how bio-based process- ing aids helped to improve the quality of PET stretch films. Its IncroMax 100 helps to extend necking and
decrease stretching load in biaxially oriented PET film. When combined with silica, it can also improve slip performance in film up to 250 micron gauge. “IncroMax 100 improves the output rate of polyesters in extrusion, while reducing energy consumption,” he said. In addition, it shows improved flow results,
through reduced stress of polymer through dies and gates, and allows extrusion at lower tempera- tures and pressures – for improved product quality. In terms of sustainability, it offers improved flow
properties – meaning a lower extrusion tempera- ture and energy savings – as well as an increased output rate. In addition, the bio-based product is suitable for use bioplastics.
Shrink performance In shrink film, an ongoing trend is to raise perfor- mance while reducing thickness. Bill Gauthier, technical service and development leader at Baystar, says that multimodal PE resins can help to satisfy this. He presented details of Baystar’s FB2230, FB1350 and FX1001 polyethylene resins. Films made from these grades can achieve a transverse direction (TD) shrinkage of 5-20% with a blow-up ratio (BUR) of <3:1. All the materials are based on Borstar 3G technology. A typical three-layer film consists of outer layers
of FB2230 and an inner layer of FB1350 – with variants of this, depending on the desired clarity. (For instance, a metallocene-based grade can be added for higher clarity.) These films have a balance of toughness, stiffness and puncture resistance, he said – and can incorporate PCR into the middle layer. Five-layer films can combine standard and
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IMAGE: GERDAU GRAPHENE
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