Really Recyclable Plastic

We are all aware of the plastic problem our planet faces. As we are made more aware of the issue, supermarkets, traders and even governments are starting to take small actions. Reducing single use plastics, banning plastic straws, charging for plastic bags etc. However, the plastic we use is still not widely recycled, so a new finding from the Berkeley Lab, at the US Department of Energy, promises to ease this plastic plight.

I’ve written many a post on plastic pollution, from research on biodegradable cutlery to enzymes that can eat our plastic problem. I too try to limit my plastic footprint using reusable water bottles, travel mugs and carrying a bag wherever I go for my shopping. These are just small things in a vast ocean of plastic we have created. Recycling seems an easy way to overcome this problem, but even the most recyclable plastic widely used, PET (i.e. poly(ethylene terephthalate)), is recycled at a rate of 20-30% of overall production; the rest ends up in landfill, taking years to break down, or is burnt. This is not a solution.recycling

Without knowing their potential harm, most plastics were not created to be recycled. Recently published research from the Berkeley Lab has founded a new way to assemble plastics, taking recycling into consideration. Currently, plastics that make everything from water bottles to car parts, are made from large polymers (i.e. smaller repeating sections (monomers) which link to form polymers). To give plastic different properties such as colour, hard/toughness, flexibility etc., extra bits are added to the monomer units. When plastics are broken down at a recycling facility, all the different features are mixed into the mass of plastic “mush” which is then recompiled to make new products. However, this new material will then have a plethora of potential features, making it difficult to work with and not recyclable more than once.pet.png

The grand idea is to have a circular system: plastic in, plastic recycled, new/better plastic out, and so on, but this is a difficult task. The research has used PDKs (i.e. poly[diketoenamines]) which have reversible bonds between the monomer units. Even if the plastic has undergone the addition of substances which make it harder, coloured, flexible etc., it will only require a dip in an acidic solution to break this all apart. They have shown not only the successful breakdown of these PDK plastics, but also their ability to be recycled into new plastics which do not possess any of the properties of the original plastic. These plastics could be recycled and improved upon in the process. Check out the time lapse below showing the plastic breakdown in acid (Credit: Peter Christensen/Berkeley Lab)

The researchers next steps are to look at using plant-based or more sustainable materials for the initial plastics, and also increase their application to include thermal and mechanical properties, making them usable in textiles, 3D printing and foams. All these findings were published in the journal Nature Chemistry last month (April, 2019).

In January 2018, our plastic problem became more evident when China officially stopped taking recyclable waste from foreign countries. The UK (for example) has drastically underfunded recycling projects and its own recycling system. This was a problem the UK government was not ready for. Before the ban, more than half of our plastic and cardboard waste went to China. Why? Our waste is now ending up (partly illegally) in sites in Malaysia, Thailand and Vietnam, and fundamentally in our oceans. As these findings come to light, and the public mood is in favour of reducing plastic pollution, now is the time for governments to invest in recycling facilities. If they invest and ensure the facilities can cater for REALLY recyclable plastics (such as the PDKs), we could finally have a circular system and start to make a real change.

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