NEXTLOOPP interview: Polymer innovation and circularity

VH: Can you explain the challenges faced in creating circular food-grade PP and the various aspects that NEXTLOOPP must address to tackle these?

EK: Polypropylene accounts for around 20% of the world’s plastic. Widely used in pots, tubs, trays and films for food packaging, it is also prevalent in non-food household and personal care products, which complicates recycling the 700,000 tonnes/ annum used in the UK alone. Approximately 300,000 tonnes per year is used as packaging.

Currently PP packaging is either going to waste-to-energy, landfill or being down-cycled into low-performance applications, wasting precious resources. Furthermore, the absence of food-grade recycled PP (FGrPP) means that all PP food packaging is currently made from virgin plastics.

Looming plastic packaging taxes have sharpened a focus on including at least 30% recycled content in packaging and transforming the way we manage our short-lived materials to minimize and reduce current waste levels.

NEXTLOOPP uses commercially-proven marker technologies to separate FGrPP and cutting-edge decontamination to ensure compliance with food-grade standards in the EU and the USA. Both of these challenges required eight years of extensive research and development to validate the ability to achieve the high standards required to convert post-consumer packaging into food-grade resins.

Major organizations including brand-owners, suppliers, universities and industry associations, through to end-users in the PP supply chain, have joined NEXTLOOPP to produce a world-first, high-quality FGrPP that will be available in the UK in 2022.

VH: What packaging design criteria should the value chain bear in mind to truly utilize the circularity potential of PP (and indeed any polymers)?

EK: Addressing packaging design for recycling is an entire topic on its own - particularly as most packaging we see these days is still being designed with the primary purpose to engage with the consumer, protect the contents within and tell a strong brand story. Unfortunately, what recyclable features it may include are not always by design and they are certainly not clearly thought through. Having said this we don’t actually need to wait for innovative designs to improve the circularity potential of PP or any other polymers.

With careful thought, re-designing a pack or bottle to be as recyclable as possible should improve its quality and reduce its cost. Here is a brief outline.

Mono Polymer design: PP Packages need to be made from a single polymer so that there is no other polymer present during the recycling process which would create incompatibility and would reduce the mechanical and technical properties of the new application.

All label no glue: Moving on down the bottle to the label we need to ditch the pressure sensitive adhesive labels that contaminate the recycling streams and opt for stretch labels or shrink sleeves. The aggressive glues are particularly an issue for recyclers and ideally options like self-peeling labels should be selected as they are already on the market. Going further, we need to ensure that these labels don’t bleed inks. The labels themselves need to be readily separated during the recycling process and recycled to avoid any unwanted waste.

Back to source: There is little point in transforming the design details without going back to the source of the actual material used in the container. Many resin manufacturers will use the minimum required stabilizer that prevents reactions that can lead to polymer degradation during processing. This in turn impacts on the quality of the recycled material especially once we enter the circular economy where plastics will go through the loop many times as the level of recycled content reaches beyond 50%.

If instead of being minimally-stabilized, the PP packages were designed for constant recycling, the plastic quality could be maintained and this would improve recycling rates. In many cases the stabilizers need to be present during their initial processing as this is where oxidation reactions can occur that can trigger later impacts through gel formation or photo-chemical reactions during outdoor exposure.

Seeing through colours: As for the rainbow of colours brands are currently deploying, this only goes to show how little deep recycling features in the design remit.

Coloured plastic packaging is much harder to recycle economically than clear plastic since there is little demand for the resulting ‘recycling grey’ that we get when we mix all these colours. Unscrambling the colours is potentially possible via sorting equipment but the multitude of colour variants means that it is impossible to produce a colour that would suit any one brand-owner.

The ironical fact is that in many cases the coloured plastic is often covered by a large label as a means of marketing, making the package below invisible. It might as well be grey or natural and save the pigment costs and improve the final recyclability!

There is no doubt that colour is one of packaging designers’ key tools yet the impact on a pack’s recyclability is huge. Tomorrow’s ideal package would be either transparent, white or self-coloured grey and shrink sleeves or self-peeling labels would be used to ensure the brand is loud and clear.

Shedding the colours of the package would vastly reduce masterbatch costs and all the design cues would be focused on the label (with self-peeling or dissolvable glue) or stretch-sleeves. Recycling yields would increase making high-quality recycled material more plentiful and less expensive. And the actual brand recycling story would be authentic.

VH: Looking at the wider polymer landscape, aside from PP, are there any other ‘newer’ forms of polymers or polymer recyclates you think are promising and that might be considered for future packaging purposes?

EK: The future of recycling should focus on the areas of greatest need. When we look at the plastics that are most widely used there is one area that deserves immediate attention and it is the area of flexible films. These products are the most widely manufactured and are used to protect many foods and yet they are recycled at very low rates. It is also important to add that the little that is recycled does not meet food-grade standards. The polymers involved are LDPE, HDPE, PP and PET and multilayer mixtures of these polymers, which adds to the complexity of recycling since these materials need to be separated into their constituent polymer families for recycling.

VH: Can you explain the importance of POLYPRISM label marking technology for achieving food-grade PP? What is the outlook for this project in the coming year?

EK: As mentioned earlier we use unique, commercially-proven marker technologies to separate FGrPP. PolyPRISM^TM applies high performing luminescent materials to labels on plastic packaging, creating what is best described as an invisible barcode for plastics recycling.

The process is surprisingly simple. Fluorescent markers - produced from non-rare earth based compounds - are printed on labels or plastic packaging sleeves.

As the mixed plastic waste runs along the conveyor belt the high-speed sorting system is triggered by an ultraviolet (UV) light source that identifies the coded PolyPRISM^TM label, reads its code and air propels it into the appropriate recycling stream.

Following extensive trials PolyPRISM^TM is now well proven in MRF setups and is plug & play ready. It is complementary to existing NIR (Near Infrared) technology and can easily be adapted to most sorting facilities around the world to target specific recycling streams such as food contact plastic packaging.

The innovative technology uses traditional labelling and branding methods and is designed to identify a host of different materials applying multiple markers for a wide range of codes. These markers can be removed during recycling leaving no traces for the next cycle of use.

We recently ran demonstration trials using PolyPRISM^TM to sort plastic packaging waste, which achieved a resounding 99.9% sorting purity at maximum production speed.

Being able to identify and sort any number of pack variants from bleach bottles to milk bottles is a world-first that will transform the way we manage the prolific volume of single-use post-consumer food packaging waste.

VH: Are there any other emerging technologies or innovations that will help NEXTLOOPP – and other such industry organizations – to achieve its circularity goals?

EK: The key areas that continue to attract the attention of engineers and scientists working in this area are those that simplify and boost the performance of the recycling stages such as:

1. Improving the techniques of separating and sorting plastic products into defined categories including food-grade but also into sub-categories such as viscosity/processability characteristics.

2. The development of removable colouration /pigmentation systems that can provide the marketing advantages of colouration yet disappear on recycling. Nature has many examples of coloured bird feathers and iridescent insects that use diffraction of light to create colour without pigments.

3. The use of very thin barrier surfaces such as glass-like coatings that minimize the absorption of formulation components by plastics and also create a safety migration barrier for any harmful residues that might be found in uncontrolled recycled plastics.

4. The use of water-less or low-water cleaning technologies that can be used to clean contaminants from post-consumer packaging to minimize the use of water and reduce waste and water treatment costs.

We are indeed continuing to work on the above challenges so that we can boost the economics and efficiency of the recycling of plastics packaging as we race to reduce and eliminate the impact of plastics in the environment and the dramatic reduction in CO2 emissions that we need to urgently achieve within the next six yea