Alicyclic Polyesters from a Bicyclic 1,3-dioxane-4-one

Congrats to Yuechao, Theona and Mitch on their new Polymer Chemistry paper! This work builds on the group’s previous report on polymerisation of DOX monomers, extending it to the incorporation of alicyclic ring connectivity through ring-opening of a bicyclic monomer- cPeDOX.

Polymerisation to the desired poly(cPeDOX) can be achieved using diethyl zinc, reaching conversions of 99% in 18 hours, although the effects of the previously reported Tishchenko reaction were observed. Copolymerisation of cPeDOX is also possible with more reactive cyclic esters, rac-lactide and caprolactone were employed as comonomers using either aluminium salen or diethyl zinc catalysts. Use of these comonomers also gives significant improvements in conversion for polymerisation of our previously reported PhDOX system.

Coca-Cola and Pepsi falling short on plastic pollution

A report released today by Tearfund revealed the failure of Coca-Cola and Pepsi, two of the world’s big plastic polluters, to provide sufficient pledges on addressing the plastic waste problem – particularly in developing countries.

Previous reports highlighted the scale of the problem, with the two giants as well as Nestle and Unilever responsible for more than half a million tonnes of plastic pollution in six developing countries each year – enough to cover 83 football pitches every day. While Unilever and Nestle scored highly in their pledges, with Unilever committing to halve their use of virgin plastics by 2025, no such public commitments have been made by Pepsi and Coca-Cola. The plastic giants are being called on to reduce their reliance on single-use plastics and switch to refillable/reusable packaging – although Coca-Cola’s current focus is on increasing recycled content and improving collection by 2030.

Urgent action is needed to tackle these issues and consistent commitments in the right direction by big polluters are necessary. However, we need to ensure that these commitments are followed up on and, more importantly, that they will have an impact. Collection will address some of the pollution problems but we need to make sure that this can then be segregated and reused/recycled and not simply be burnt or end up in landfill.

Can we social distance from single- use plastics?

As coronavirus bears down on society, the use of single-use plastics has stepped up. Panic buying in the wake of the virus means demand for hand sanitiser, antibacterial wipes and much more besides (toilet roll) has rocketed. Although the plastic revolution since Blue Planet 2 has put emphasis on reuse and recycling, the threat of a global pandemic has shifted these concerns to the back of people’s minds.

But it is not just packaging where this demand for single-use plastics has soared. Plastics are ubiquitous in healthcare, enabling time consuming and costly sterilisation processes to be replaced with versatile polymers that can be used in an array of hygienic medical equipment such as masks, aprons, wipes, bags, cannulas etc. In other words, single-use plastic has been a global life saver and its role is becoming increasingly prevalent throughout this pandemic. So should we, as has been proposed in various avenues, do away with plastic? The medical practice in particular highlights that we cannot, instead we require a rethink surrounding their material value. Recycling of plastics in the UK is currently riddled with problems – much of it is shipped abroad, incinerated or rejected due to contamination.

Obviously, not all plastics are suitable for reuse (particularly contaminated medical waste), so recycling routes such as chemical recycling then come into play. With the right infrastructure, we can ensure that these classically “unrecyclable” plastics can become part of this circular process.

For more info see Dr Helen Holmes and Mike’s recent article as well as our interdisciplanary “One Bin” project, which aims to standardise plastic waste collection.

UK to Encourage Recycled Content Increase

It was great to see the UK government show ambition towards reducing our plastic waste challenges in their recent budget announcement. From 2022, a levy will be placed on firms that do not have at least 30% recycled content in their packaging, which is predicted to increase the use of recycled plastic materials by up to 40%. By placing impetus on the producer, we should also begin to see demand for new plastic begin to reduce in this respect.

However, there are real challenges with any blanket policy like this. Why is 30% a target? Is that reasonable for all types of plastic in all types of products? We’ve seen clearly in our lab that different polymers – or even the same polymer in different products – have drastically different recycling parameters. 30% as a hard and fast rule is not ambitious enough for some, and an unreachable target that will sacrifice product integrity for others…

While reducing use of new plastic and increasing demand for recyclate is good, it is important to maintain high quality of this recycled content – particularly after multiple mechanical recycling cycles. An efficient waste management system of all plastics is needed to keep up with this increased demand, and indeed improves the quality of our recyclate. Our fear is that the price of reaching this recycled content will increase – as we do not have enough quality recyclate to hand – and this will offset avoiding the levy. Packaging coming out of this must also then be recyclable, not be used as filler in unrecyclable black plastic or composites, thus avoiding replacing one type of plastic waste with another. A more nuanced approach is needed, built on evidence and infrastructure investment. Blanket bans and interventions are easy for governments to do, but have real consequences when you cannot meet demand across the supply chain.

Encouraging the valorisation of plastic waste through these measures is important – but in the end won’t mean much if we do not have the collection and processing system is there to keep up.

The Challenges of Ending Plastic Waste

While we normally try and discourage science chat in our group pub trips, this was an exception. In the first RE3 public engagement event of 2020, Mike represented the GML and Henry Royce Institute as one of a team of experts discussing the challenges of ending our plastic waste problem in the UK.

Pint of Science Jan 2020

Mark Miodownik , Claudia Henninger and Helen Holmes completed the panel to give a broad perspective on the many issues that need to be overcome to end our plastic waste problem. Interrogated by an enthusiastic Mancunian audience, multiple aspects were discussed ranging from the false saviour of biodegradables to changing the behaviour of the fashion industry.

Much has been made of becoming plastic-free as an end-all solution to our waste problem and its negative impacts on the environment. However, as was stressed both at the event and in a recent BBC article, we need systems that prioritise the environmental impact of buying….not one that simply reduces plastic, which often remains the best material for the job.

While this valuable insight certainly highlighted the sheer size of the problem facing us as a society, it is encouraging that the public took such an interest in how best to move forward. Engagement events like these are vital to eradicate confusion around what can be done with our waste and to build public pressure to push ideas forward.

Do biodegradables have their PLAce?

A recent BBC article discussed the merits of both biodegradable and compostable plastics in addressing our throwaway culture. Both the UK and Canada are set to ban single-use plastics in the next two years and alternatives that will not accumulate in landfill or the environment need to be found and established, fast.

With our existing infrastructure, a lot of currently available alternatives to petroleum based plastics are simply replacing one form of plastic waste with another. This is demonstrated within compostable packaging standards – which say that industrial scale composting conditions must be able to break-down the material over 12 weeks leaving pieces no bigger than 2mm. Industrial compositing conditions are far more forcing than household waste, boosting the need for collection schemes to enable such changes. If the plastics don’t make it to the correct conditions then they may simply break down into smaller pieces that are not “composted” and cause more problems than the original.

Its important to remember however that, as with chemical recycling, biodegradables and compostables have their place. The two are distinctly different, and would therefore need differing standards in their widespread use. These materials can particularly play a part in invisible waste streams, such as adhesives and plastic films. These receive less attention due to their difficulty to recycle and relatively smaller size but are a large contributor to our plastic waste problem.

Chemical recycling – all its cracked up to be?

Over 50% of plastic produced each year is discarded after a single-use, contributing to the never ending stream of plastic waste both in the UK and internationally. While plastic remains the best material for the job in a lot of cases, we need to make smart choices with how this is reused, recycled or biodegraded. The GML is an active participator in the RE3 project aiming to address some of these issues in the UK. Currently most of this waste stream is recycled mechanically, which requires separation and is not compatible with all material input – could chemical recycling be the answer we’ve all been looking for?

A collaborative effort amongst US universities recently reported the upcycling of single-use polyethylene into high quality petroleum products in the latest effort to add value to the 40bn tonnes of plastic waste projected to be present on Earth by 2050. This breakthrough has been covered a lot in the news and the BBC asked Mike for his thoughts. Its important to realise the forcing conditions that are still required in this process, with temperatures of 300 °C for over 30 hours, while platinum is by no means a cheap metal to employ. However, chemical recycling, if it can be optimised, could become a key part of the recycling infrastructure in the UK. The process may avoid the need for sorting our waste streams, saving money and time – while converting this mix to a useful feedstock with real value.