What began as a legitimate concern about the amount of plastic we use (and throw away) has quickly evolved into what some would call a ‘knee-jerk’ reaction.

As we have covered extensively, single-use plastics have perhaps been singled out as the big culprits, but the material in general has seen something of a beating. We’ve all heard frightening statistics, such as that from the Ellen MacArthur foundation that there could be more plastics than fish in the sea by 2050. And yes, when you see images of plastics washed upon the shore it is usually rigid containers.

So while nobody would argue that reducing rigid plastics waste – or indeed any waste – where possible is a good thing, a little of the nuance has been lost along the way. If used responsibly, plastic is a valuable material. It helps protect our medicines. It keeps our food fresher for longer. It is light and relatively cheap to manufacture.

And yet, according to the Ellen MacArthur Foundation, 95 per cent of the value of plastic packaging material, worth $80-120 billion annually, is lost to the economy.

“Indeed, we are seeing certain retailers removing packaging while acknowledging that food waste will increase," says Adrian Whyle, Resource Efficiency Senior Manager, PlasticsEurope. "This happens at a time when we are faced with the challenges of global warming, and increasing food poverty even in the most developed countries. Our priority has to be to maximise the preservation and shelf-life of perishable resources, while at the same time securing their quality and safety.” 

In the EU, less than 30 per cent of plastic waste is recycled today. Compare this to say, Japan, which recycles almost 85 per cent of its PET bottles.

What we need, then, is change the way we look at plastics. To change the way we consume, dispose of and recycle them in order to make them a valuable part of a circular economy – not part of the problem. Many would argue we already have the technologies available to do this, but as yet we have not found a way to implement them effectively on a wider scale.

The sheer scale of the plastics waste problem cannot be denied or ignored. But given the value of this material, its protective qualities and low production costs, it’s unlikely we will be seeing it consigned to the history books in the near future. This being the case, it is imperative that we find a more efficient, sustainable way to manufacture and deal with it.

Building a circular economy

The use of recycled plastic feedstocks is an integral part of our move towards a circular economy, as it would decrease the demand for virgin resources. And with growing consumer awareness of the problem of plastic waste, there is a greater appetite for rigid plastics with higher recycled content. The industry certainly seems more actively committed to increasing the recycling and reuse of plastics, as evidenced by the Plastics 2030 voluntary commitment.

Creating more value from plastic waste by using more recycled materials in rigid plastics can only be a good thing in principle. But there are challenges to be faced, not least in terms of the varying quality results when it comes to the use of recycled content. To many, despite claims to the contrary, there is a question mark over the quality of a package made from higher percentages of recycled feedstocks. How high can we go before, for example, barrier protection becomes an issue?

The extent to which the amount of recycled content will affect how the material and machinery will perform depends upon the ratio of ground-up plastic that is mixed with the virgin materials.

“One of the biggest challenges is that how the polymer blend will perform varies from batch to batch,” says Kevin Heap of Sumitomo (SHI) Demag. “This makes it more challenging to optimise machinery process settings, which in turn reduces the efficiency of the processing machinery which affects the bottom line.”

Efforts are being made to improve the recyclability of recycled plastic feedstock – such as for example through the use of increasingly sophisticated lab and blending techniques.

It is clear that rPET has great potential. But in addition to quality, another problem the industry struggles with is scaling: put simply, we have not yet devised a system to produce quality recycled feedstocks in the amounts needed to make them a real commercial force. The good news is efforts are being made to address this. To give just one example, Repsol recently introduced its Reciclex project, through which it says it aims to address the shortage of recycled material with the consistent quality required by the market.

Finally, there’s also a trust issue regarding the use of reground plastics, particularly in relation to contamination. Any plastics for food applications need to carefully evaluate the compliance risks.

A look at black plastics

It seems to have become a kind of accepted wisdom in some quarters that ‘black plastics can’t be recycled’.

The reality, of course, is slightly more complex. Technically, as we know, all plastics can be recycled, and black is no different. The issue is not with the material itself, but more with how it can be efficiently separated from the waste stream in order to avoid colour contamination. This is a particular problem in the UK, where the optical machines that sort plastics for recycling can’t detect the carbon black pigments, meaning that a great deal of recyclable material will be sent to incineration or, even worse, landfill.

Then why do we use black plastics all if this is the case? Why not stick to clear, or light blue, which makes for a greatly simplified recycling stream? Many assume that it is purely aesthetic – that brand owners are answering consumer demands for a more ‘premium’ feel to certain packaging.

In fact, it’s not all about the look of the product. “The reason that I understand is that, one, it’s a useful colour to prevent damage to the food as it prevents light getting in; and two it helps things to stay cooler,” says Jennifer Baxter of the Institute of Mechanical Engineers. “But we are seeing a movement away from that, such as for example food products coming in oven-ready cardboard.”

Some supermarket chains – Lidl, for example – have been phasing out black plastics entirely, while last year Quorn announced it would be eliminating black plastic from its packaging. But as usual, an outright ban would seem to ignore the potential technologies that could address this issue. There may be indeed be viable solutions.

To give just one example, Irish company Quinn Packaging has introduced what it claims is the ‘first fully recyclable black plastic tray’, the Detecta food tray. Quinn’s solution has been to create its own black colour additive, which it says makes the trays easily identifiable, allowing them to be sorted on existing Near-Infra-Red sorting equipment.

This is also an area in which chemical recycling may hold great potential, says Adrian Whyle of Plastics Europe: “In the future when the technology for chemical recycling has achieved maturity, [black plastics] will provide ideal feedstock for conversion back to virgin plastics.”

Lighter doesn’t mean weaker – spotlight on injection compression moulding

As the pressure on brand owners mounts to reduce the environmental impact of their products across the entire lifecycle, the need to reduce the weight of their packaging grows.

But what about the entire environmental impact of a product’s life cycle – not just the CO2 the package itself uses up during transport? Some would argue that weight is only one part of the question. That while it is desirable to have as light a package as possible, reducing the wall thickness of a plastic package can reduce its barrier effectiveness and mechanical properties, thereby creating more food waste. And as I heard someone say recently: “The least sustainable option of all is product waste.”

Injection compression moulding to reduce wall thickness is just one technology that may have potential for dealing with this issue, says Kevin Heap of Sumitomo (SHI) Demag.

Compared to conventional thin wall injection moulding, he tells us, where faster filling and higher pressures are required to drive molten plastic material into thinner cavities to prevent it freezing off between shots, injection compression moulding presses the plasticised material into moulds to ensure even distribution. This method is particularly suited to ultra-thin plastic packaging, particularly food and FMCG lids and containers.

“Today’s lightweight plastics offer a combination of superior functionality, strength, shatter resistance and barrier properties. With injection compression moulding, packaging suppliers can now reduce the wall thickness of containers and lids from 0.45mm to 0.35mm. This saves around 25 per cent in raw polypropylene materials compared to the standard injection moulding process, while maintaining comparable mechanical properties.”

He adds that stack moulds – a series of moulding faces ‘stacked’ together to create multiple faces or levels for moulding – are increasingly used along with injection compression moulding to increase productivity by distributing the plastic melt onto two more or more separate mould parting surfaces.

“I have seen one project where reducing the balanced sections of the wall thickness for margarine tubs and lids saved between 20 and 40 per cent in weight,” adds Mr Heap. “This Thin Recess Injection Moulding (TRIM) was developed and patented by StackTeck of Canada. The company uses an advanced approach to thin out parts of the wall section well beyond the conventional thin wall packaging approach used for polyolefins with high melt flow indexes.”

The ‘challenge from flexibles’

Much has been made of recent reports that rigid plastic packaging is under a growing threat from flexibles, particularly the stand-up pouch. The reasons behind this are relatively easy to understand: flexible plastics use fewer resources and less energy than other forms of packaging. They can provide significant reductions in packaging costs, material use, transport costs – added to which there are performance advantages in terms of increasingly sophisticated hot-fill and barrier technologies.

But maybe ‘challenge’ is the wrong word - it is not necessarily a case of either/or. While flexible stand-up pouches have good preservative properties and can be used for food, pharmaceutical or cosmetics packaging, at the moment they are generally constructed from multiple layers of film or other flexible substrates, which can make them challenging to recycle.

And there are many applications for which rigids may be the clear choice. The protective and preservative properties of rigid plastics are well-recognised, allowing more delicate products such as soft fruits or baked goods to reach the consumer safely following long transit.

“We do not see that rigid plastics are in competition with flexible packaging,” says Adrian Whyle of PlasticsEurope. “The each bring their own benefits. Flexible packaging is ideally suited for products such as toothpastes, cat food, confectionary products etc., and helps to further minimise the total weight of the packaging. However, for many applications a rigid container is the best solution, e.g. laundry products, carbonated beverage containers and larger containers such as milk bottles or engine oil.”