MULTI-LAYER PACKAGING | MATERIALS
Packaging producers are continuing to develop multi-layer structures using single materials, which maintain properties like toughness and barrier performance with better recyclability
Sustaining advances in multi-layer packaging
A key challenge for producers of multi-layer packaging is recyclability. Many traditional designs use multiple polymers – making them difficult, if not impossible, to recycle economically. One approach has been to boost the properties of polyolefins such that they can then form the majority – or entirety – of the packaging, making it easier to recycle. Several speakers at the recent Multilayer
Flexible Packaging conference – organised by AMI – presented examples in this area.
Barrier method Anvit Gupta and Martin Antensteiner of ExxonMobil co-presented a paper on the design of polyethylene- rich formulations in barrier packaging. Polyamide (PA) is commonly used within flexible
packaging to add barrier properties. However, recycling the two at the end of life can be a problem. The presenters said that EVOH can often be used to replace PA and make recycling easier. Some of the reasons include: PA’s higher
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melting temperature; compatibility issues; and potential contamination of recycling streams. “EVOH can provide an oxygen barrier similar to
PA-containing film while not posing the same potential challenges to mechanical recycling streams,” they said. Barrier film needs a range of attributes including toughness, cost-saving potential, shelf appeal and seal integrity. ExxonMobil’s solutions rely on several of its polyolefin grades including Exceed and Vistamaxx, in formulations that use either less PA or none at all.
In one case it has produced 180-micron cast film
with reduced PA content. The original design included a PA/EVOH/PA barrier layer – with a total PA content of around 26%. A new design used PA as the outer layer – offering stiffness, and resistance to abrasion and heat – plus an EVOH oxygen barrier and two grades of Exceed. Here, the PA content has been reduced to around 15%. The new film allows a 40% reduction in PA layer thickness. It is processed
September 2024 | FILM & SHEET EXTRUSION 13
Main image: ExxonMobil has created formulations for polyethyl- ene-rich
thermoform- able barrier film
IMAGE: SHUTTERSTOCK
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