Associations & Federations Michael Stephen Column

Response to Association of Plastic Recyclers (FREE)

Today Michael responds to the Association of Plastic Recyclers (APR) in the USA

I have been reading a report in Recycling News on 11th April, of a statement by the Association of Plastic Recyclers (APR) in the USA that “Claims regarding the recyclability of degradable additives are unfounded, untested and possibly misleading   …. as No third-party testing data has confirmed these recyclability claims.”

The additives themselves are not of course intended for recycling, but extensive third party testing has been done on plastic products made with them – see Recycling

I asked one of Symphony Environmental’s scientists who specialises in oxo-biodegradable plastics, what he thought of this APR statement and he said that plastics containing masterbatches such as d2w can be safely recyled without separation:

“The use of prodegradant additive systems does not cause any change which does not ordinarily occur in the equivalent conventional plastics. Conventional plastics suffer oxidative degradation during processing, and during repeated mechanical recycling. This is due to the processing temperature and physical stresses of extrusion, in combination with defects present in the molecular structure of all polymers; as well as added impurities – intentional and otherwise – principally metallic species including mineral fillers and pigments. 

Reaction of the polymer with oxygen during processing leads to chain-cleavage and a loss in molecular weight, which in turn results in loss of mechanical properties.

Therefore during initial extrusion and subsequent recycling, unstabilised polymers are vulnerable to degradation, and would often not be stable for their intended service life and subsequent mechanical recycling. Therefore, conventional plastics are routinely protected from thermo-oxidation by the inclusion of antioxidant stabilisers which delay or prevent oxidation.

Conventional plastics also suffer oxidation during exposure to sunlight, leading to rapid failure, and fragmentation into microplastics, but degradation is too slow to reduce the molecular weight enough to permit biodegradation in a meaningful time frame. The stabilizers used to preserve the integrity of conventional short-life plastics such as packaging, offer little protection from sunlight, so for long-life plastic items such as garden furniture, a special stabiliser is always included.

At ambient temperatures oxidation is strongly dependant on sunlight exposure. Therefore while initial degradation is rapid, fragmented plastics are often occluded from sunlight and have the tendency to accumulate in the environment as microplastics – plastics degraded beyond the point of failure but not yet biodegradable.

In order to deal with this problem, prodegradant masterbatches such as d2w are used. They work by accelerating photo-oxidation and/or thermo-oxidation, so that oxidation of littered plastic occurs much more rapidly, whether in sunlight or not.  The d2w masterbatch also includes stabilisers to prevent the onset of degradation until outdoor exposure at the end of useful life.

Mechanical recycling of plastics is rightly focused on products that are valuable for recycling, such as thick-walled materials – for packaging this often means PET bottles and containers. By contrast, the use of prodegradant additives is primarily focused on thin-film single-use packaging, which is more likely to escape into the environment as litter.  For these latter materials, recycling rates have historically been poor, because it makes little sense in economic or environmental terms to recycle them. Recycling is therefore of little relevance to products in which d2w is used.

Nevertheless, the French product specification AFNOR Ac T-51-808 (2012), and the BPA  industry Standard Standards  establish criteria to ensure that polyolefins made with prodegradant systems, not only oxidise sufficiently and rapidly, but also continue to oxidise in dark conditions.  They also ensure that the product is not vulnerable to oxidation prior to disposal, in order to permit a functional life and to permit recycling where appropriate. Reputable prodegradant masterbatch suppliers evaluate each product to ensure the right balance between stability and prodegradant effect.

Unlike compostable type plastics (which are entirely non-recyclable in normal waste streams and will contaminate conventional waste streams), degradation is not an intended disposal route. Reputable providers agree that the priority for any material is to maintain circularity so far as is practicable – this means designing products with their first life functionality, reuse, collection, and waste disposal in mind – including recycling.

For the majority of single-use thin film packaging applications, the secondary goal (in case the material escapes into the open environment as litter) is to facilitate abiotic oxidation of the polymer which is not dependant on continued sunlight exposure and will therefore continue until it becomes a material which is readily biodegradable. 

Academic studies by Jakubowicz (2011) and Babetto (2019) used prodegradant additive at extreme inclusion rates (up to around 10 times normal levels), to demonstrate potential impact on mechanical recycling.  The authors conclude that even at these very high levels any effect on a product made with the recyclate will be neutralised by the stabilisers normally used in conventional plastics.

In 2016 Transfercenter für Kunststofftechnik (TCKT) Austria TCKT Report recycled LDPE film with a prodegradant additive system and found that not only did the film made from the recyclate retain thermal stability after reprocessing, but the impact of the stabiliser was greater than the effect of the prodegradant – resulting in thermal stability which actually increased with the proportion of recyclate containing prodegradant additive.

This is also the experience of technology providers such as Symphony Environmental, and routinely demonstrates that, because of the stabilisation system, recyclate containing oxo-biodegradable plastics can actually be more resistant to thermo-oxidation.  

In a follow-up to their work mentioned above, TCKT explored later in 2016 Weathering Study on LDPE the potential for recyclate from oxo-biodegradable plastic to be used for long-term outdoor applications. The study found that plastics made with recyclate with and without prodegradant additive, both failed rapidly during sunlight exposure; but conventional stabilisers already used in the manufacture of outdoor products, were successful in preserving the products with and without the additive.

These studies demonstrate that recycling of oxo-biodegradable plastics can be safely achieved up to 100%, but in most real life post-consumer recyclate streams the contribution of the prodegradant additive system will be much more diluted.” 

Michael Stephen

Michael Stephen is a lawyer and was a member of the United Kingdom Parliament, where he served on the Environment Select Committee. When he left Parliament Symphony Environmental Technologies Plc. attracted his attention because of his interest in the environment. He is now Deputy Chairman of Symphony, which is listed on the AIM market of the London Stock Exchange, and is the founder and Chairman of the Oxo-biodegradable Plastics Association.

Earlier Postings in this Column

All articles of Michael Stephen can be found here

Interview with Michael Stephen


The opinions expressed here by Michael Stephen and other columnists are their own, not those of

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