Ensuring reliable traceability coding in a changing world of plastic types

The Global plastic waste problem.

Plastic waste is a huge area of concern globally. The Big Plastic Count, the UK’s largest plastic waste survey conducted by Greenpeace UK and Everyday Plastic, found that in the UK alone an estimated 90 billion plastic pieces are discarded annually, with less than 20% of that recycled – snack foods and fruit and vegetable packaging being some of the largest contributors to plastic waste.

Driving plastic sustainability.

New rules are starting to be introduced to tackle the problem. In the UK, EU (European Union) and globally, Governments are introducing legislation and action plans, such as the UK and EU Plastic Tax, EU Plastics Strategy, and EU Circular Economy Action Plan, with the aim to encourage companies to reduce, reuse and recycle packaging.

Increasingly, there is a drive for manufacturers to ensure that the weight and volume of packaging are minimised, to reduce the amount of plastic packaging waste generated. Companies and consumers want to play their part in the change and are increasingly demanding more recyclable and renewable plastics from suppliers and manufacturers.

Changing plastic packaging.

Major consumer brands are starting to make real changes in the use of plastics, including moving towards lighter films, or more recycled and recyclable materials. As a result, flexible packaging is experiencing elevated levels of growth globally.

Flexible plastics are typically very thin types of PE (polyethylene) and PP (polypropylene) that may be overprinted and coextruded or laminated with other materials to achieve a good oxygen (gas) barrier and strength-to-weight ratio.

With the current worldwide focus on sustainability and reducing plastic waste, many manufacturers are moving towards flexible laminated films of PE (such as LDPE (Low Density PE) and HDPE (High Density PE), PP, and OPP (oriented polypropylene) to reduce the amount of plastic used. These films are typically used as flow wrap films and pouches for dry and fresh foods and household products.

Mono-plastic packaging, made from a single type of plastic, such as polyethylene, is also growing due to its recyclability.

Code adhesion and traceability.

The increasing use of laminated flexible films and mono-plastics can bring manufacturers challenges when it comes to traceability code adhesion, due to the surface energy of these plastic types.

PET is easier to mark as it has a higher surface energy due to oxidised functional groups in its structure, such as C=O and -OH, which makes it easier for ink to adhere to. However, plastics such as PP & PE have lower surface energies due to the plastics not containing any of these oxidised functional groups. Instead, they have hydrophobic hydrocarbon chains which means traceability code adherence is more challenging.

As a result, manufacturers are finding that their ink jet inks that have adhered to their packaging in the past, are now struggling to adhere to the newer packaging – codes often smudge or can be rubbed or scratched off in production or transit, and alternative specialist inks are typically required to overcome this challenge.

The use of laminated flexible films and mono-plastics is expected to grow further, which means manufacturers need inks that are specifically formulated for these lower surface energy plastics to ensure full traceability for their products, and avoid costly fines, rejects and reworks.

CIJ inks today need to be capable of adhering reliably to lower surface energy flexible films and mono-plastics, making ink an important consideration when looking for a new CIJ printer.

Considerations for traceability marking solutions.

Legislation and regulations are continually changing. When looking for a new CIJ printer to print onto plastic packaging, here are some important considerations:

  • Ensure you choose a printer that has an ink specifically formulated for these types of lower surface energy plastics, with the ink having undergone the necessary stress-adhesion tests
  • Request sample marking of the ink on your substrate, or better, request a printer trial to check the adhesion on your substrate in your manufacturing environment and process
  • Check the proposed ink conforms to safety standards and incoming legislation, such as inks that are PFAS-free (Per- and polyfluoroalkyl substances) and CMR-free (Carcinogenic, Mutagenic and Reprotoxic) fluids
  • Verify that the inks comply with standards such as the EuPIA (European Printing Ink Association) Exclusion Policy
  • Understand the dry time and shelf-life for the ink
  • Ask questions on printer reliability and printhead cleaning intervals, specifically how the inks have been formulated and tested in the printer.

Data references:

Home | The Big Plastic Count
eaa6997d-survey-results-global-plastics-treaty.pdf (greenpeace.org)
b9f6a209-survey-results-global-plastics-treaty-executive-summary.pdf (greenpeace.org)

The UK’s Largest Plastic Waste Survey Reveals 1.7 Billion Pieces of Plastic Packaging Still Being Thrown Away by Households Weekly | Greenpeace UK

New EU rules to reduce, reuse and recycle packaging | News | European Parliament (europa.eu)
EU packaging waste generation with record increase – Eurostat (europa.eu)

The UK’s Leading Plastic Trade Association (bpf.co.uk)
What You Need to Know About the Plastics Treaty – Earth Day