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The subject of downgauging is something we have covered extensively in Packaging Europe, and it continues to be one of the main sustainability drivers. Victoria Hattersley looks at some of the many ways in which the industry is approaching this challenge.

We’re all aware that there has been a general trend for some years now towards reducing the weight of packaging of all varieties. But while this is still a priority, a key point to note from the start is that it is by no means the ‘Holy Grail’. There are many different factors to consider.

“Looking at it from a sustainability aspect, downgauging is just one of various possibilities to decrease the CO2 footprint,” says Thomas Kahl, Project Manager Eco Solutions, Mondi Consumer Packaging. “It’s important to take a step back and look at packaging that is fit for purpose in a holistic manner.”

It may seem a little contradictory to start an article on the topic of downgauging by pointing out that it is not the most important thing. But sustainability is not a case of choosing a single, ‘correct’ route, so much as factoring in different priorities – recyclability, resource efficiency and waste reduction being just three of the most widely discussed in our magazine – and attempting to navigate the best path between them.

In particular, when we think about the overall sustainability of a package, we have to consider not only the energy used to produce it, the CO2 used in transport and so on, but also the protection of the product itself. If this is damaged or destroyed, then any energy expended to make and transport it will have been entirely wasted.

Whether it is rigids, flexibles, plastics, aluminium, the question we should ask when it comes to downgauging is perhaps not so much how light can we go, as how can we downgauge as far as possible while still ensuring that the package provides adequate product protection and being recyclable where possible.

From rigid to flexibles

That being said, of course downgauging is something that should still feature highly on the R&D agendas of all companies across the supply chain. “Using fewer resources, and thereby being more sustainable, is fundamental,” said Romain Cazenave, Packaging EMEA Marketing Director at Dow. “We know that recycling and reuse are key to the circular economy, but how often do we focus on the third ‘R’ - reduce?

“Industries for which plastics are essential are rising to the ‘reduce’ challenge, although this smarter approach is nothing new. For example, the weight of the typical 500ml drinks bottle has been halved in the last two decades, thanks to technologists.”

While weights of both rigid and flexible plastics have continued to reduce, there does seem to be a general consensus that flexibles offer the greatest opportunities for lightweighting and material reduction.

Dow – whose applications for industrial packaging include stretch films, stretch hoods, collation shrink and heavy-duty shipping sacks – has also achieved considerably thinner gauges. It says its stretch wrap film has been cut from 23 microns to 12, stretch hoods from 100 microns to 80, collation shrink films from 50 to 40 microns, and so on.

“The thickness reduction for all these applications is achieved via the combination of material development, in the form of new polymer material designs, and multilayer film structure development to facilitate the optimum combination/configuration of new materials. Only by a combination of these two approaches can we achieve these significant thickness reductions,” added Romain Cazenave.

Elsewhere, at the end of last year, Mondi’s Styria division launched two films developed for multilayer BIB liquid products – Styria Form Bar 50 and Styria Form Bar 90 DW. With the former, Mondi says it is the first company to be able to replace the usual 66- or 70-micron barrier film with a 50-micron film. The Styria Form Bar 90 DW is a monolayer film that measures 90 microns in thickness, by replacing two-ply film with a 70-micron barrier and a 45-micron polyethylene layer. This, says Mondi, results in a material reduction of around 20 per cent.

“We tell our customers that if they move from rigid to flexible plastics, they have the opportunity to save up to 70 per cent of the materials, which is obviously a massive reduction,” said Thomas Kahl. “Flexible plastic is more resource efficient than some alternatives and it has a very low packaging to product ratio. Added to this, it has excellent product preservation.”

Reducing complexity

We should also bear in mind that downgauging isn’t even just about reducing the weight of materials used – it’s also about reducing the complexity. While barriers are essential for product preservation and efficiency, we know that sometimes the use of multiple layers of materials can cause problems when it comes to recycling. If the layers can’t be easily separated, then they cannot easily be recycled either. To confuse things further, whether such films are recycled can also depend on individual countries’ recycling or collection infrastructure.

Hence the increased focus on offering monomaterial structures, which are both lighter in weight and more recyclable, as they can all go into a single waste stream. “If we look at downgauging in the sense of using less material, as opposed to simply weight reduction, then it is a case of using monomaterials wherever possible,” said Thomas Kahl.

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In the past it was generally accepted that the thinner a material structure is, the lower the barrier properties will be. But it doesn’t necessarily have to be a case of either/or anymore, as technologies grow ever more sophisticated. Many new monomaterial structures can offer barriers but still be recyclable. The above-mentioned Mondi is just one company making strides in this area, for applications where multilayers are not necessary or appropriate.

For example, it recently introduced a fully recyclable detergent product solution with the German company Werner & Mertz, owner of the Frosch brand of cleaning products. This is a mono-material pouch made from polyethylene with detachable decorative panels, which will replace conventional flexible packaging for Frosch products. When the pouch is empty, the two components – unprinted pouch and printed banderole – can be shredded and sorted into separate recycling streams to generate recycled material equivalent in quality to the original.

Not all about plastics

It’s not all about plastics, of course – even if they are currently receiving the majority of the attention thanks to our current poor recycling and collection infrastructure. Manufacturers of packaging made from other materials are also putting considerable R&D efforts into the downgauging process.

Colep, for example, a European producer of tinplate aerosols, has been continuously investing in lightweighting its tinplate aerosol cans by decreasing the thickness of its rolled steel. “The big challenge is to keep or improve the mechanical properties and performance of our cans with considerably less materials,” said Jose Oliveira, industrial director, Packaging division, Colep.

The company recently collaborated with Henkel to deliver tinplate cans for the brand owner’s hair styling brand Syoss with weight reductions of 18 per cent – which it says is a significant saving associated with the classic three-piece tinplate can manufacturing process.

“Always at the forefront of our minds is ‘how to do better with less’, which inspired us to develop the right combination of different tinplate grades used in three-piece cans that comply with the strict guidelines imposed by FEA standards and legislation. The new downgauging solutions have the same recyclability as the classic solutions. Tinplate is classified as a ‘forever’ material without restrictions in recyclability.”

Reduction at the nanoscale

Moving aside from the more ‘conventional’ approaches to downgauging, it is also worth giving a brief mention of the growing possibilities offered by nanotechnology – specifically graphene nanotubes – to both increase wall strength while downgauging at the same time.

How is this achieved? Without becoming too technical, graphene nanotubes have a number of unique characteristics that make them ideally suited to packaging applications. Their tensile strength is approximately 100 times greater than steel, owing both to their interlocking carbon-to-carbon covalent bonds, and to the fact that each nanotube consists of one large molecule, which means it doesn’t have the weak spots found in other materials. They also have excellent conductivity – and therefore anti-static properties – as well as thermal stability up to 1000°C.

But for the purposes of this article, it is the strength factor we particularly want to highlight, as this is what brings the biggest potential for downgauging. According to Christoph Siara, sales and marketing director of graphene nanotubes specialist OCSiAl, “Increased bonding strength between molecules as well as the strength of individual molecules could allow us to reduce the gauge of a single layer.”

OCSiAl is one example of a company that produces single-wall graphene nanotube solutions (those which consist of a single graphene cylinder rather than several concentric cylinders) for packaging applications.  

“The presence of our TUBALL solution in additive packages would allow us to enhance their efficiency, while laminates build-up, suitable for specific applications, can be modified due to the enhanced performance of single layers (some of which could be eliminated, leading the way for increased use of mono-materials),” said Mr Siara.

The potential for this still-evolving technology is certainly huge, but as with any emerging technology there are questions as well as answers. There is still, for example, a debate over the use of nanotechnology for food contact purposes that needs to be addressed.

A balancing act

As our world increasingly wakes up to the growing climate crisis, sustainability has long since stopped being a gimmick or a marketing tool for companies. It’s an obligation – a necessity.

As we have often pointed out, when it comes to the packaging industry, achieving the best solution is a complex balancing act. Downgauging is still important – particularly where it can be achieved with little to no product damage – but it has to be seen as just one of many factors in the overall drive towards a greener future.