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.