Poor quality rPET limits use in packaging, finds WRAP

By Joseph James Whitworth contact

- Last updated on GMT

Related tags: Polyethylene terephthalate, Packaging

Improving food grade rPET quality for use in packaging
Improving food grade rPET quality for use in packaging
Poor recycled polyethylene terephthalate (rPET) quality is limiting its use in new food and beverage packaging, according to Waste and Resources Action Programme (WRAP).

Converters, retailers and brand owners identified the discolouration and colour variability of rPET as the primary quality issue affecting its adoption into packaging.

In packaging, rPET makes up between 20-30% of the content of plastic bottles compared to virgin polymers, according to WRAP, but this could grow to 50% if quality was acceptable.

For thermoformed products (e.g. trays) addition rates are typically up to 50%, however these could also be at levels of up to 75-100% if resin quality was improved, said the UK-based organisation​.

Improvements to the quality would enable more to be used in new food packaging to reduce its environmental impact (e.g. the use of one tonne of rPET in drinks bottles saves around 1.5 tonnes of CO2​).

Industry reaction

Alan Davey, LINPAC Packaging Innovations Director, told FoodProductionDaily.com: "Quality is declining and we, as a leading manufacturer in the food packaging market, are having to invest more and more money to deal with a declining quality of materials.

"We have filters and detectors on our machines to stop it getting through to the final product but obviously that’s an expense we could well do with out and we have to dispose of it ultimately.​ This slightly declining quality has happened over the last three years.

"Another factor is that bottles are being continually light-weighted, which is also adding to the problem. A third aspect is that PET bottles are being used for lots more things like household cleaners where they have combined metal and plastic trigger devices on top of the PET bottle."

He added: “We still use high levels of recycled products, over 90% in many cases.”

Frank Coleman, operations director at Holfeld Plastics, told us: "From Holfeld perspective, we have previously invested heavily on machinery and equipment to enable us to cope with quite high levels of contaminates such as metal, paper etc ( super clean process) we have not noticed a fall in quality from our current approved supplier base but prices are high (compared to virgin).

"We also have not seen a shortage, but this is probably linked to price, as we have contracts in place so suppliers are probably have to pay dear for the right quality feedstock."

Bottle bale issues

Bottle bales used to contain 85-90% bottles, but now most deliveries (>90%) of bales have poor quality with up to 30-40% contamination and it is that it is getting worse from a PET perspective.

Quality issues for rPET resin include discolouration and colour variability, presence of small coloured particles and small particles/fines, which increase the level of black specks, gels and general degradation of material.

However, particles smaller than 2mm cannot currently be efficiently sorted, so there needs to be advanced sorting technologies and systems for purification of small PET particles to increase overall PET flake purity and reduce any potential material losses, said the report.

Feedback and data on rPET quality came from PET reprocessors, rPET bottle and sheet converters and brand owners and retailers that use rPET in packaging applications.

rPET quality factors

Factors affecting the quality of rPET are caused by a combination of packaging design, quality of recovered bottle bales and reprocessing methods.

Converters, retailers and brand owners have all identified the discolouration and colour variability of rPET as the primary quality issue affecting the adoption of rPET into packaging.

Variation in rPET colour is also a key concern as it often varies from dark blue/grey to dark brown to yellow/brown.

PET reprocessors identified an overall shift from mixed bottle bales to mixed plastic bales (including pots, tubs and trays) from UK sources over the past three years, resulting in a reduction of PET content of bales.

Some reprocessors said their processes were struggling to keep up with the changes in bale composition.

Those designed to process mixed bottles-only were experiencing difficulties in separating PET from mixed plastics bales but more modern facilities were better able to handle a wide range of plastics.

The survey feedback from both reprocessors and converters suggested that industry protocols or guidelines from organisations such as EPBP or Association of Post-Consumer Recyclers (APR) are not widely used, or perhaps not as well-known as would be expected.

Key contaminants listed by the reprocessors (in order of occurrence from the survey results):

PVC

Other non-bottle plastics including black plastics

Silver and other solid colours used for PET bottles/trays

Metals (aluminium cans and metal springs from trigger packs

Plastic films, bags, carrier bags

Paper

Glass

Silicone

Other plastics heavier than water (PS, HIPS, ABS

Fines, dirt, loose labels

 Rubber

Black specs concern

The presence of black specs in rPET is an issue for reprocessors and converters that melt filter PET flake, said the report.

UK converters said improvements in rPET pellet and flake quality have been achieved by reprocessors in the last three years, which they attributed to better sorting at UK PRFs and investment into separation technologies and equipment.

However converters experience problems with rPET resins and there is concern over a wide variation in rPET quality, particularly flake, across their suppliers, resulting in the need to test regularly and manage their own quality standards.

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