PDK: are endlessly recyclable plastics becoming a reality?

Changing plastic’s life cycle from linear to circular

With plastic being an incredibly sturdy, durable, and one of the most versatile materials around, the rate at which it is produced has increased significantly over the last couple of decades. However, due to the limited possibilities for recycling and the fact that plastic can take up to a thousand years to decompose, the processing of plastic has become one of the biggest environmental challenges that we are currently facing and plastic waste has been a massive problem for many years now. Most of the plastic that is produced is quickly discarded and ends up in incinerators, landfills, or in our oceans – Greenpeace reported that 12 million tonnes of plastic enter our oceans every year. Only a small portion of plastics – less than a quarter of what is produced – is recycled, but this is a costly and energy-intensive process, and even these plastics have a linear lifecycle and eventually become unusable.

Plastic soup in the Southern Atlantic Ocean (source)

In order to divert plastic from the oceans and landfills, a more efficient method of recycling is required. With the recycling processes that are currently in use, the already small portion of plastic that is recycled significantly declines in its quality in the recycling process, and the resulting product is hardly ever used in high quality products after being recycled. This is due to the many different chemical additives that most plastics contain to give it its characteristics such as the texture, colour, and shape. After disassembling the polymers that the plastic is built up from, these additives are still attached to the plastic’s monomers with immutable bonds. At the recycling plant, these monomers, with their particular set of additives still attached, end up in a large mixture with different monomers, each with varying sets of additives that determined the qualities of the original product. Because of this large mixture of monomers with countless different chemical additives, it becomes extremely difficult to predict the qualities that the end-product will inherit from the original material. As a result, Science Daily explains, the recycled plastic is usually subject to a decrease in quality and performance. 

As a result, (recycled) plastics have never had a circular life-cycle. That is, until last week when a new research by a team of researchers at the U.S. Department of Energy’s Berkeley Lab, published in Nature Chemistry, introduced a new kind of plastic that can be recycled in closed-loop life cycles. This new material, called poly(diketoenamine) or PDK, contains reversible instead of immutable bonds that, when dunked in a highly acidic solution, allow the plastic to be broken down into its original monomers. Additionally, when disassembled into monomers, the PDKs can be freed of any chemical additives in this acidic solution. These “purified” monomers can in turn be reassembled into polymers, creating new, high quality plastics, thereby allowing them to be fully recycled and be turned into new plastics that don’t necessarily inherit the features of the original material. In short, any plastic product can be turned into any other plastic product.

Process of disassembling PDK plastic (source)

The idea to approach plastic recycling at a molecular level is not completely new and it has been attempted in the past. In the execution of comparable methods, researchers ran into issues with the retrieval of the monomers of “regular plastics” due to irreversible bonds in the polymers, making this process a difficult and costly endeavour. Here, with the relative ease with which the original monomers can be recovered and the fact that this process can be repeated over and over again, PDKs offer an exceptional to provide a plastic with a circular life-cycle with a minimal environmental impact.

4 thoughts on “PDK: are endlessly recyclable plastics becoming a reality?

  1. Hey Juul,
    What are some of the obstacles that this kind of recycling faces? would it be able to compete on a large scale? have large scale facilities already been made?


  2. Hi Juul,
    Thanks for introducing this new type of plastic. Similar to Jake, I was wondering what the downsides of this type of plastic is also looking at the production costs? Secondly, do you reckon this would be a solution on its own or that it be combined with overall plastic use?


  3. Hey Juul, do you think that PDK plastic bags will be better for the environment than biodegradable bags? While I like the idea of circular recycling that PDK bags will introduce, I’m skeptical whether this will decrease the amount of bags just thrown away, as this would require a big shift in people’s actions. Biodegradable bags are not as dependent on a change of behavior, due to their faster decomposition time it’ll be less of a burden if just thrown away. I don’t agree with this behavior, but I have the feeling that this change in type of bags would be accepted easier.


  4. Hey Juul, you mentioned that the process of recycling is often energy intensive and costly. A large amount of plastic waste flooding into the oceans comes from less wealthy states. do you thing this type of recycling would be a viable option to curb these sources of emissions?


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