Recycled polyethylene, rPE for short, is obtained by turning polyethylene that previously existed as a product or as production scrap back into granules. In the industry it is also often referred to as “regranulate”. In bag production, rPE is used on its own or blended with virgin raw material.
Interest in recycled material has grown with the agenda of both using raw material resources efficiently and reducing packaging waste. This interest makes it more important to know how rPE is obtained and in which bags it can be used, and how.
What sets rPE apart from other raw materials is that it has a history rather than being a chemical type. A batch of rPE can come from HDPE, LDPE, LLDPE or a mixture of these; its properties depend largely on this history.
Where does rPE come from?
Recycled polyethylene has two main sources. The first is production scrap: edge trim from film extrusion, film produced during set-up, and waste from cutting and sealing. This material is usually clean and its type is known; it can be collected and reclaimed in the same plant and fed back into production.
The second is post-consumer material: used and discarded packaging, bags and films. This material is collected, sorted, washed, shredded, melted and filtered, and turned back into granules. Because of the variety of sources, the properties of post-consumer rPE can vary more from batch to batch.
Reclamation step by step
Turning post-consumer polyethylene back into raw material goes through a few basic stages. Each stage directly affects the quality of the resulting granules.
- Sorting: Polyethylene is separated from other plastics, paper and metal.
- Shredding and washing: The material is broken into small pieces; soil, labels and food residues are cleaned off.
- Drying: Moisture is removed; this step is important to prevent bubbles forming in the film.
- Melting and filtering: The pieces are melted in an extruder, and the melt is passed through screens to remove foreign matter.
- Granulating: The melt is cut into granules and packed in batches.
Where is it used in bag production?
rPE is most commonly used in products where appearance is secondary. Dark-coloured garbage bags are a well-known example: the dark colour covers colour variations in the recycled material. In bags expected to look light-coloured or clear, the use of rPE is more limited, because shade differences between batches are more easily noticed.
- Garbage bags: The most established use of rPE.
- Courier and packaging bags: Especially in the inner layer of multi-layer films.
- Industrial films: Function-focused applications such as protective covers and transport packaging.
Co-extrusion offers an important possibility here. When rPE is placed in the middle layer and virgin raw material is used in the outer layers, the film’s print surface and sealing layer remain more predictable while recycled content is still used. The proportion of rPE in the film is determined by the product’s use and the buyer’s specification.
What to watch for when using it
Working with rPE requires more control than virgin raw material. Differences between batches can be reflected directly in film quality. For this reason, many manufacturers prefer to blend rPE with virgin raw material in a set proportion to make both processability and film properties more predictable.
- Flow differences: The melt flow of material from different sources can vary; line settings may need to be reviewed.
- Gels and contamination: Unmelted particles and foreign matter can create specks, holes or weak spots in the film.
- Colour and odour: The colour shade can vary from batch to batch; some batches may have a noticeable odour.
- Strength: Degradation of the material during previous processing can reduce film strength; thickness and blend are planned accordingly.
How is quality monitored?
In plants that reclaim their own production scrap, the job is relatively easy: the type, colour and history of the material are known. Edge trim and set-up waste can be shredded, turned back into granules and reused in a set proportion in the production of the same type of film. For post-consumer material bought in from outside, however, this information relies on batch records from the supplier and on checks carried out at intake.
In production that uses rPE, raw material intake checks become more important. The batch’s source, colour and flow behaviour are recorded; a trial run shows whether the film meets expectations. During production, the screen pack may need to be checked more often.
A business ordering bags that contain rPE also has questions to ask: what are the source and proportion of the recycled material, how much variation in colour and appearance should be expected, and how will strength checks be carried out? Discussing the answers to these questions in advance reduces surprises at delivery.
On the finished bag, checks for thickness, seal strength, tearing and visual defects are applied as rigorously as in production with virgin raw material. When properly planned, rPE can be a meaningful complement to virgin raw material in function-focused bags.