High efficiency value-added bulk recycling of polymers by solid state shear milling

Over 300 million tonnes of plastic is produced annually and this is expected to double over the next 20 years. Plastics have become vital materials in many aspects of everyday life but the generation of plastics solid waste (PSW) is becoming an increasing problem, for example 8 million tonnes of plastic waste finds its way into the oceans each year, having a huge impact on marine ecosystems. Some relatively clean and easy to separate types of waste plastics can be recycled economically, such as drinks bottles, and levels of recycling are increasing but many polymeric materials are much more difficult to recycle, for example composites containing different materials of polymers which cannot be re-melted such as rubber tyres and printed circuit boards. As such there is an urgent need worldwide to develop new technically and economically feasible methods to recycle these types of materials. This aligns with the concept of a circular economy which seeks to keep products and materials in use and design out waste and pollution.

Our joint UK-China team aims to develop an industrial scale continuous process to successfully recycle and re-manufacture currently difficult to recycle bulk waste streams, with high efficiency. A continuous milling process will be developed to break down solid polymeric waste into fine powders with controlled properties, which can then be reprocessed into value-added products. We will perform experiments to understand the mechanisms of the milling process and how these can be opitimised for particular waste streams. We will characterise the materials produced and examine different ways of turning these powders into useful, value-added products.

We combine unique skills and strengths of our Chinese and UK groups to address key issues facing both of our countries - effectively reducing the significant amount of plastic waste with efficient routes to re-use. This proposal builds on the highly successful research collaborations over the last decade between the world-class research laboratories of the Polymer IRC at Bradford and Sichuan University State Key Laboratory for Polymer Materials Engineering (SKLPME), an important and international award-winning part of our RCUK Bradford Science Bridges China platform.

This programme focuses on the global issue of solutions for bulk difficult to recycle waste polymers. We aim to develop a recycling process which will convert waste materials into fine powders, and then to re-use these materials in new value-added products. As such there will be a clear national and international societal benefit in reducing the amount of waste plastic and an associated environmental benefit through reduction in the amount of waste which will be disposed of by landfill or leaked into waterways and oceans. This aligns well with the strategic priorities of the UK and China governments, evidence by recent legislation.

Our project aims to make high value added products from controlled manufacturing routes which exploit our underpinning scientific knowledge in a resource efficient manner, by significantly enhancing the properties or functionality of specific polymers, creating added value. The proposal aligns strongly with the Circular Economy agenda, which aims to promote recycling and re-use and move away from the traditional make-use-dispose economic model. This approach is now of first order importance in both the UK and China. There will be direct benefit to the UK and China economies, initially through our collaborator companies in the UK and China, who will be involved in the later stages of the programme to help bring the technology to full scale. More widely there will be an economic benefit to the recycling industry with the introduction of a new technology which will broaden the type and amount of waste polymer materials which can be recycled. There will be an associated benefit to machinery manufacturers and processors, through the introduction of a new manufacturing route.

There will also be a wider benefit to public perception related to polymers and how they are used. Polymers are too good to waste - they are chemically rich and made predominantly from oil which a rich source of energy but one which around 90% of is burned. It makes little sense to scrap polymers having invested energy in making these important and highly useful materials. We aim to disseminate the findings of our research widely through both scientific and general media (for example our research has previously been highlighted on Chinese television channel CCTV) in order to promote the recycling initiative.

Through the scientific underpinning of the research carried out within the programme, there will be direct benefits to the associated scientific and academic community. Research groups working in the fields of polymer recycling and waste management will benefit from understanding of the solid shear milling technology. The wider polymer research community will benefit from improved understand of the types of blended and composite materials which can be formed form recycled fine powders. Groups working in other fields such as the food and pharmaceutical industries will also benefit from exposure to the solid state shear milling, leading to new applications of the technology.